Mrophy Richards DRM27024
Paul Rigg
buying. The price seems pretty good for FM, AM (including DRM) and Band 3
and L Band DAB.
The reviewer does suggest that sensitivity and tuning might be an issue and
looking at the list of transmissions that might be available I'm not sure
that there would be anythung much of interest to receive here in Yorkshire
(assuming that we would be within the skip distance of Wooferton)
Does anybody have any experience of it?
DAB sounds worse than FM
Poor sound quality
Poor reception qulaity
Poor ease-of-use
Avoid.
--
Steve - www.digitalradiotech.co.uk - Digital Radio News & Info
The adoption of DAB was the most incompetent technical
decision ever made in the history of UK broadcasting:
http://www.digitalradiotech.co.uk/dab/incompetent_adoption_of_dab.htm
Kristoff Bonne
Paul Rigg schreef:
I cannot comment on the radio itself as I do not have one, but as it
also has SW, you should be able to pick up quite some station in DRM on SW.
The review from Chris Mackerell of NZDX (who does have quite some
experience with DRM, see http://www.owdjim.gen.nz/chris/radio/DRM/) does
not seams to be that bad at all!
Cheerio! Kr. Bonne.
DAB sounds worse than FM
The actual review is here:
http://www.owdjim.gen.nz/chris/radio/DRM/MorphyRichardsReview.pdf
I agree with him that it was very fiddly to use, but as far as sound quality
and DAB receptino quality goes it was poor.
The only good thing about it is that it's got an impressive feature list,
but I totally disagree with his view that it's a good portable radio for
normal radio listening, which is what he says it is - it's one of the worst
I've ever had to review in that respect.
Kristoff Bonne
DAB sounds worse than FM schreef:
>> The review from Chris Mackerell of NZDX (who does have quite some
>> experience with DRM, see http://www.owdjim.gen.nz/chris/radio/DRM/)
>> does not seams to be that bad at all!
> The actual review is here:
> http://www.owdjim.gen.nz/chris/radio/DRM/MorphyRichardsReview.pdf
> I agree with him that it was very fiddly to use, but as far as sound quality
> and DAB reception quality goes it was poor.
Well, it's strange that you seams to get such a different results than
Chris. Are you sure your receiver wasn't defective?
As there is no "operational" DAB in NZ, it's normal he didn't really
test that part, but he did say he got very good reception for AM, FM and
DRM.
What interests me is how the DRM reception stood up next to the AM
broadcasts. There are a number of stations that broadcast both in AM and
DRM (like the BBC WS, DW and RNW) so it would be interesting to do a
comparision between the two.
How good is the receiver sensitivity for DRM vs. AM.? (concidering the
fact that the DRM broadcasts are usually at a lower power-level then
those in DSB-AM)?
And, what would be most interesting, how well does DRM deal with fading
on SW?
Paul,
BTW. There is a yahoo group specific on this radio. Perhaps there are
more people overthere with practicle experience.
http://groups.yahoo.com/group/mrdrmradio/
Cheerio! Kr. Bonne.
DAB sounds worse than FM
> Steve,
>
>
> DAB sounds worse than FM schreef:
>>> The review from Chris Mackerell of NZDX (who does have quite some
>>> experience with DRM, see http://www.owdjim.gen.nz/chris/radio/DRM/)
>>> does not seams to be that bad at all!
>
>> The actual review is here:
>> http://www.owdjim.gen.nz/chris/radio/DRM/MorphyRichardsReview.pdf
>
>> I agree with him that it was very fiddly to use, but as far as sound
>> quality and DAB reception quality goes it was poor.
>
>
> Well, it's strange that you seams to get such a different results than
> Chris. Are you sure your receiver wasn't defective?
If it was defective I would have said it was defective.
> As there is no "operational" DAB in NZ, it's normal he didn't really
> test that part, but he did say he got very good reception for AM, FM
> and DRM.
From memory, it defaulted to stereo reception on FM even though it's only
got one speaker, so I had to change the settings to make it default to mono
because with stereo it was a bit hissy. I'm not sure I even tried AM
reception, because the AM stations are on DAB anyway. Reception quality on
DAB was poor relative to other DAB radios. The sound quality was poor
relative to other DAB radios. And when I tried playing back high bit rate
MP3 files via the SD card it still sounded poor.
> What interests me is how the DRM reception stood up next to the AM
> broadcasts. There are a number of stations that broadcast both in AM
> and DRM (like the BBC WS, DW and RNW) so it would be interesting to
> do a comparision between the two.
I remember that the DRM stations were sometimes available and sometimes not.
There were typically 2 or 3 DRM stations available at any one time. I can
remember looking into whether I should be able to receive the statinos
permanently, but I can't remember what I found out.
Basically, the radio may be okay for DXing purposes, but for the vast
majority of ordinary radio listeners it's not a good buy.
> How good is the receiver sensitivity for DRM vs. AM.? (concidering the
> fact that the DRM broadcasts are usually at a lower power-level then
> those in DSB-AM)?
>
> And, what would be most interesting, how well does DRM deal with
> fading on SW?
Can't remember, because I wasn't reviewing it on the basis of it being used
for DXing.
Kristoff Bonne
DAB sounds worse than FM schreef:
>>>I agree with him that it was very fiddly to use, but as far as sound
>>>quality and DAB reception quality goes it was poor.
>>Well, it's strange that you seams to get such a different results than
>>Chris. Are you sure your receiver wasn't defective?
> If it was defective I would have said it was defective.
>>As there is no "operational" DAB in NZ, it's normal he didn't really
>>test that part, but he did say he got very good reception for AM, FM
>>and DRM.
> From memory, it defaulted to stereo reception on FM even though it's only
> got one speaker, so I had to change the settings to make it default to mono
> because with stereo it was a bit hissy. I'm not sure I even tried AM
> reception, because the AM stations are on DAB anyway. Reception quality on
> DAB was poor relative to other DAB radios.
These are all reception-issues, so it's strange you had these results
which where completely different from what Chris had.
Looks more like you had a defective model, perhaps something wrong with
the antenna-cabling.
What did Morphy Richard answer to this?
>>What interests me is how the DRM reception stood up next to the AM
>>broadcasts. There are a number of stations that broadcast both in AM
>>and DRM (like the BBC WS, DW and RNW) so it would be interesting to
>>do a comparision between the two.
> I remember that the DRM stations were sometimes available and sometimes not.
> There were typically 2 or 3 DRM stations available at any one time. I can
> remember looking into whether I should be able to receive the stations
> permanently, but I can't remember what I found out.
That's not really the question.
The question was a comparison between reception in DSB-AM and DRM.
Did you also do the tests on SW in DSB-AM at the same time and in the
same conditions?
How much interference from other sources (computers, TVs,
ethernet-over-power, ...) was there at that time?
> Basically, the radio may be okay for DXing purposes, but for the vast
> majority of ordinary radio listeners it's not a good buy.
(...)
>>How good is the receiver sensitivity for DRM vs. AM.? (concidering the
>>fact that the DRM broadcasts are usually at a lower power-level then
>>those in DSB-AM)?
>>And, what would be most interesting, how well does DRM deal with
>>fading on SW?
> Can't remember, because I wasn't reviewing it on the basis of it being used
> for DXing.
As there are no local DRM broadcasts (on MW or LW) in the UK (appart
from a trial and the BBC WS), what else would this radio be for, then
for DX?
To bad.
This is one of the first "customer grade" DRM-capable receivers on the
market, so it should have been interesting to try out -at least- that
part and make a good comparison between DRM and DSB-AM?
BTW. Did the AMSS work (e.g. on 198, 234 or 648 Khz)?
Cheerio! Kr. Bonne.
DAB sounds worse than FM
> Steve,
>
> DAB sounds worse than FM schreef:
>>>> I agree with him that it was very fiddly to use, but as far as
>>>> sound quality and DAB reception quality goes it was poor.
>>> Well, it's strange that you seams to get such a different results
>>> than Chris. Are you sure your receiver wasn't defective?
>> If it was defective I would have said it was defective.
>
>
>>> As there is no "operational" DAB in NZ, it's normal he didn't really
>>> test that part, but he did say he got very good reception for AM, FM
>>> and DRM.
>> From memory, it defaulted to stereo reception on FM even though it's
>> only got one speaker, so I had to change the settings to make it
>> default to mono because with stereo it was a bit hissy. I'm not sure
>> I even tried AM reception, because the AM stations are on DAB
>> anyway. Reception quality on DAB was poor relative to other DAB
>> radios.
>
> These are all reception-issues, so it's strange you had these results
> which where completely different from what Chris had.
>
> Looks more like you had a defective model, perhaps something wrong
> with the antenna-cabling.
>
>
> What did Morphy Richard answer to this?
It wasn't a defective model. If you read the person's review he hardly had
anything to say about FM, so I doubt he actually bothered to do much
listening on FM. The review was baiscally just a review for DXing anoraks.
>>> What interests me is how the DRM reception stood up next to the AM
>>> broadcasts. There are a number of stations that broadcast both in AM
>>> and DRM (like the BBC WS, DW and RNW) so it would be interesting to
>>> do a comparision between the two.
>
>> I remember that the DRM stations were sometimes available and
>> sometimes not. There were typically 2 or 3 DRM stations available at
>> any one time. I can remember looking into whether I should be able
>> to receive the stations permanently, but I can't remember what I
>> found out.
>
> That's not really the question.
>
> The question was a comparison between reception in DSB-AM and DRM.
> Did you also do the tests on SW in DSB-AM at the same time and in the
> same conditions?
No. The review I did was for non-anoraks.
> How much interference from other sources (computers, TVs,
> ethernet-over-power, ...) was there at that time?
My computer wasn't far away. At the end of the day, if a radio can't be used
when a computer is switched on nearby then it's of no use to non-anoraks.
>> Basically, the radio may be okay for DXing purposes, but for the vast
>> majority of ordinary radio listeners it's not a good buy.
>
> (...)
>
>>> How good is the receiver sensitivity for DRM vs. AM.? (concidering
>>> the fact that the DRM broadcasts are usually at a lower power-level
>>> then those in DSB-AM)?
>>> And, what would be most interesting, how well does DRM deal with
>>> fading on SW?
>> Can't remember, because I wasn't reviewing it on the basis of it
>> being used for DXing.
>
>
> As there are no local DRM broadcasts (on MW or LW) in the UK (appart
> from a trial and the BBC WS), what else would this radio be for, then
> for DX?
The radio can receive DAB, FM, AM, SW, it's got an SD card - and it can
receive DRM as well.
> To bad.
> This is one of the first "customer grade" DRM-capable receivers on the
> market, so it should have been interesting to try out -at least- that
> part and make a good comparison between DRM and DSB-AM?
>
>
> BTW. Did the AMSS work (e.g. on 198, 234 or 648 Khz)?
Didn't try it. DRM was basically unreliable in that you never knew whether a
station was going to be there or not when you turned the radio on. I have
about 900 words to describe all the features and the reception and sound
quality. 900 words isn't much, and you certainly aren't able to cover things
as irrelevant to ordinary consumers as AMSS.
Basically, DRM is a waste of time for ordinary radio listeners.
jami...@excite.com
> From memory, it defaulted to stereo reception on FM even though it's only
> got one speaker, so I had to change the settings to make it default to mono
> because with stereo it was a bit hissy.
Again Steve demonstrates his total lack of cluefulness. The mono
speaker carries L+R combined, and when the two channels are combined
all the FM stereo hiss disappears and switching the actual tuner to
mono would make no difference.
Kristoff Bonne
DAB sounds worse than FM schreef:
>> These are all reception-issues, so it's strange you had these results
>> which where completely different from what Chris had.
>> Looks more like you had a defective model, perhaps something wrong
>> with the antenna-cabling.
>> What did Morphy Richard answer to this?
> It wasn't a defective model. If you read the person's review he hardly had
> anything to say about FM, so I doubt he actually bothered to do much
> listening on FM.
You clearly had a problem for all modes that use the telescopic antenna:
SW, FM and DAB; so it looks you did have a general problem.
So, what did the customer-service engineers of MR had to say on this?
Didn't they offer to sent you another receiver to exclude the problems
you have are due to this particular box?
>> The question was a comparison between reception in DSB-AM and DRM.
>> Did you also do the tests on SW in DSB-AM at the same time and in the
>> same conditions?
> No. The review I did was for non-anoraks.
Is that a reason not to test this?
>> How much interference from other sources (computers, TVs,
>> ethernet-over-power, ...) was there at that time?
> My computer wasn't far away. At the end of the day, if a radio can't be used
> when a computer is switched on nearby then it's of no use to non-anoraks.
Is that a reason not to test it?
By the way, that's not the point, is it.
The question is if the problem you had where due to signal-level (i.e.
sensitivity of the radio), interference (i.e. an external influence) or
something else.
The best way to know this is simply tune in on AM. If you have
computer-interference, you would have noticed it immediatly.
How can you judge a technology if you do not know if the problem you are
experiencing are due to your particular receiver, external influence or
the technology itself?
Even if the article you where asked to write wasn't about SW, it did
give you a change to do some real life tests with a new technology.
For me, that would be more then sufficient reason to get my curiosity
started!!!
>> As there are no local DRM broadcasts (on MW or LW) in the UK (appart
>> from a trial and the BBC WS), what else would this radio be for, then
>> for DX?
> The radio can receive DAB, FM, AM, SW, it's got an SD card - and it can
> receive DRM as well.
Sure, but DAB, FM, AM, SD-cards and SW are quite common. DRM isn't.
You actually have one of the few new radios which incorperate a new
technology, and you "forget" to test it?
?????
>> To bad.
>> This is one of the first "customer grade" DRM-capable receivers on the
>> market, so it should have been interesting to try out -at least- that
>> part and make a good comparison between DRM and DSB-AM?
>> BTW. Did the AMSS work (e.g. on 198, 234 or 648 Khz)?
> Didn't try it. DRM was basically unreliable in that you never knew whether a
> station was going to be there or not when you turned the radio on.
And you never asked yourself why that was?
> I have
> about 900 words to describe all the features and the reception and sound
> quality. 900 words isn't much, and you certainly aren't able to cover things
> as irrelevant to ordinary consumers as AMSS.
Is that a reason not test it?
> Basically, DRM is a waste of time for ordinary radio listeners.
That's a bit a strange statement from an engineer who fails to ask the
question if the problem he is experiencing is due to the technology, the
enviroment it is used in or the particular box he is using.
Cheerio! Kr. Bonne.
DAB sounds worse than FM
> Steve,
>
>
>
> DAB sounds worse than FM schreef:
>>> These are all reception-issues, so it's strange you had these
>>> results which where completely different from what Chris had.
>>> Looks more like you had a defective model, perhaps something wrong
>>> with the antenna-cabling.
>
>>> What did Morphy Richard answer to this?
>
>> It wasn't a defective model. If you read the person's review he
>> hardly had anything to say about FM, so I doubt he actually bothered
>> to do much listening on FM.
>
> You clearly had a problem for all modes that use the telescopic
> antenna: SW, FM and DAB; so it looks you did have a general problem.
>
> So, what did the customer-service engineers of MR had to say on this?
>
> Didn't they offer to sent you another receiver to exclude the problems
> you have are due to this particular box?
There was nothing wrong with it other than it was insensitive. This is not a
fault.
>>> The question was a comparison between reception in DSB-AM and DRM.
>>> Did you also do the tests on SW in DSB-AM at the same time and in
>>> the same conditions?
>
>> No. The review I did was for non-anoraks.
>
> Is that a reason not to test this?
Yes, the review was not going to be read by anoraks.
>>> How much interference from other sources (computers, TVs,
>>> ethernet-over-power, ...) was there at that time?
>
>> My computer wasn't far away. At the end of the day, if a radio can't
>> be used when a computer is switched on nearby then it's of no use to
>> non-anoraks.
>
> Is that a reason not to test it?
Yes, the review was not going to be read by anoraks.
> By the way, that's not the point, is it.
>
> The question is if the problem you had where due to signal-level (i.e.
> sensitivity of the radio), interference (i.e. an external influence)
> or something else.
> The best way to know this is simply tune in on AM. If you have
> computer-interference, you would have noticed it immediatly.
AM would have been its usual crackly self, so I doubt it would have proved
anything.
> How can you judge a technology if you do not know if the problem you
> are experiencing are due to your particular receiver, external
> influence or the technology itself?
>
>
> Even if the article you where asked to write wasn't about SW, it did
> give you a change to do some real life tests with a new technology.
>
> For me, that would be more then sufficient reason to get my curiosity
> started!!!
Good for you.
>>> As there are no local DRM broadcasts (on MW or LW) in the UK (appart
>>> from a trial and the BBC WS), what else would this radio be for,
>>> then for DX?
>
>> The radio can receive DAB, FM, AM, SW, it's got an SD card - and it
>> can receive DRM as well.
>
> Sure, but DAB, FM, AM, SD-cards and SW are quite common. DRM isn't.
DXing is not hte only reason to buy this radio,whcih is what you suggested.
> You actually have one of the few new radios which incorperate a new
> technology, and you "forget" to test it?
>
> ?????
But I did get good DRM reception at times, so what's your point? The fact is
that DRM stations weren't always available.
>>> To bad.
>>> This is one of the first "customer grade" DRM-capable receivers on
>>> the market, so it should have been interesting to try out -at
>>> least- that part and make a good comparison between DRM and DSB-AM?
>>> BTW. Did the AMSS work (e.g. on 198, 234 or 648 Khz)?
>
>> Didn't try it. DRM was basically unreliable in that you never knew
>> whether a station was going to be there or not when you turned the
>> radio on.
>
> And you never asked yourself why that was?
But I did get good DRM reception sometimes. I put it down to vagaries of
long distance radio transmissions.
>> I have
>> about 900 words to describe all the features and the reception and
>> sound quality. 900 words isn't much, and you certainly aren't able
>> to cover things as irrelevant to ordinary consumers as AMSS.
>
> Is that a reason not test it?
Yes, because the review was not going to be read by anoraks.
>> Basically, DRM is a waste of time for ordinary radio listeners.
>
> That's a bit a strange statement from an engineer who fails to ask the
> question if the problem he is experiencing is due to the technology,
> the enviroment it is used in or the particular box he is using.
What, so you want me to recommend an expensive portable radio that can't be
used near computers? Yeah, great idea.
Kristoff Bonne
DAB sounds worse than FM schreef:
>>> It wasn't a defective model. If you read the person's review he
>>> hardly had anything to say about FM, so I doubt he actually bothered
>>> to do much listening on FM.
>> You clearly had a problem for all modes that use the telescopic
>> antenna: SW, FM and DAB; so it looks you did have a general problem.
>> So, what did the customer-service engineers of MR had to say on this?
>> Didn't they offer to sent you another receiver to exclude the problems
>> you have are due to this particular box?
> There was nothing wrong with it other than it was insensitive. This is not a
> fault.
Of course it can be a fault; like cabling-issues between the module and
the antenna.
So we are back at square one, aren't we?
How come that your test showed much worse reception-results then then
tests done by Chris?
So what did the customer-services of Morphy Richard actually had to say
about this?
>>>> The question was a comparison between reception in DSB-AM and DRM.
>>>> Did you also do the tests on SW in DSB-AM at the same time and in
>>>> the same conditions?
>>> No. The review I did was for non-anoraks.
>> Is that a reason not to test this?
> Yes, the review was not going to be read by anoraks.
That's not the question.
The question is "it the fact that the review you where asked to write
was for non-technical users a reason not to test something else, just
out of pure intellectual interest?"
>> By the way, that's not the point, is it.
>> The question is if the problem you had where due to signal-level (i.e.
>> sensitivity of the radio), interference (i.e. an external influence)
>> or something else.
>> The best way to know this is simply tune in on AM. If you have
>> computer-interference, you would have noticed it immediatly.
> AM would have been its usual crackly self, so I doubt it would have proved
> anything.
Was that AM on the SW, on the same frequencies used by the DRM stations?
>>>> As there are no local DRM broadcasts (on MW or LW) in the UK (appart
>>>> from a trial and the BBC WS), what else would this radio be for,
>>>> then for DX?
>>> The radio can receive DAB, FM, AM, SW, it's got an SD card - and it
>>> can receive DRM as well.
>> Sure, but DAB, FM, AM, SD-cards and SW are quite common. DRM isn't.
> DXing is not hte only reason to buy this radio, which is what you suggested.
YOU are not buying something!
You are giving the opportunity to play around with a new piece of
broadcasting-technology and write an "expert opinion" about it afterwards.
>> You actually have one of the few new radios which incorperate a new
>> technology, and you "forget" to test it?
>> ?????
> But I did get good DRM reception at times, so what's your point? The fact is
> that DRM stations weren't always available.
And the question is "why?"
It could be related to the broadcaster (does not broadcast continuesly,
does not fill in the correct information in the "alternative frequency"
entries in DRM or AMSS datastream).
If could be related to the receiver (does not use the AF-information
correctly).
It could be related to local aspects (local interference at these new
frequencies, or more or less interference at different times of the day).
It could be related to this particular receiver (sensitivity at
different frequencies).
Did you check that the broadcasters where supposted to be broadcasting
at that time and at what frequency?
Did the receiver tune to the correct frequency?
Did you get someting on AM on these frequencies at these times?
How much was the local interference at these frequencies at these
particular moments?
>>> Didn't try it. DRM was basically unreliable in that you never knew
>>> whether a station was going to be there or not when you turned the
>>> radio on.
>> And you never asked yourself why that was?
> But I did get good DRM reception sometimes. I put it down to vagaries of
> long distance radio transmissions.
Or it can be related to local events, like smebody in your neighbourhood
using a ethernet-over-powerline connection from time to time.
There are quite a lot of source of interference what are not continues
at all.
Where I live; there seams to be a source of interference which pops up a
couple of times an hour (for about half a minute) which blanks out all
LW, MW and SW, and -to some degree- also up to band II (FM).
>>> I have
>>> about 900 words to describe all the features and the reception and
>>> sound quality. 900 words isn't much, and you certainly aren't able
>>> to cover things as irrelevant to ordinary consumers as AMSS.
>> Is that a reason not test it?
> Yes, because the review was not going to be read by anoraks.
But YOU are surely interested in more then just what you are going to
end in the review, aren't you?
>>> Basically, DRM is a waste of time for ordinary radio listeners.
>> That's a bit a strange statement from an engineer who fails to ask the
>> question if the problem he is experiencing is due to the technology,
>> the enviroment it is used in or the particular box he is using.
> What, so you want me to recommend an expensive portable radio that can't be
> used near computers? Yeah, great idea.
That is, unless there is a way you can hook it up to a antenna outside
where you do get a strong enough signal that does not get interupted.
(a bit like you hoop up a satellite-receiver to a antenna outside the
house, or a freeview receiver to a rooftop antenna outside the house).
Of course, this radio does not have an external antenna-connector; but
there is a difference in saying in your review "DRM sucks" and "the fact
that this radio does not have an external antenna sucks".
And what did the Morphy Richards customer-service engineers propose to
solve the issues you reported?
Cheerio! Kr. Bonne.
DAB sounds worse than FM
> Steve,
>
>
>
> DAB sounds worse than FM schreef:
>>>> It wasn't a defective model. If you read the person's review he
>>>> hardly had anything to say about FM, so I doubt he actually
>>>> bothered to do much listening on FM.
>
>>> You clearly had a problem for all modes that use the telescopic
>>> antenna: SW, FM and DAB; so it looks you did have a general problem.
>>> So, what did the customer-service engineers of MR had to say on
>>> this? Didn't they offer to sent you another receiver to exclude the
>>> problems you have are due to this particular box?
>
>> There was nothing wrong with it other than it was insensitive. This
>> is not a fault.
>
> Of course it can be a fault; like cabling-issues between the module
> and the antenna.
FM reception was okay. DRM reception was okay some of the time but other
times stations weren't available, and I think you've said that they're not
always available anyway. DAB reception quality wasn't very good, but it
wasn't a fault, it was just because the receiver was relatively insensitive,
some radios are.
> So we are back at square one, aren't we?
> How come that your test showed much worse reception-results then then
> tests done by Chris?
Chris said he hardly listened to DAB, and I didn't notice him saying
anything about DAB reception. As for DRM reception, I don't live in New
Zealand, do I?
All I could say is what I experienced, which was that DRM wasn't very good
because I could only receive up to 3 stations, some of those were silent at
times (i.e. no reception problems, just silent - can't remember which
statino that was) and other times I couldn't receive certain statinos, such
as WS, but I vaguely remember that the coverage area doesn't cover the UK or
somethign daft.
>>>>> As there are no local DRM broadcasts (on MW or LW) in the UK
>>>>> (appart from a trial and the BBC WS), what else would this radio
>>>>> be for, then for DX?
>>>> The radio can receive DAB, FM, AM, SW, it's got an SD card - and it
>>>> can receive DRM as well.
>>> Sure, but DAB, FM, AM, SD-cards and SW are quite common. DRM isn't.
>
>> DXing is not hte only reason to buy this radio, which is what you
>> suggested.
>
> YOU are not buying something!
>
> You are giving the opportunity to play around with a new piece of
> broadcasting-technology and write an "expert opinion" about it
> afterwards.
And that's what I did.
> And what did the Morphy Richards customer-service engineers propose to
> solve the issues you reported?
Morphy Richards is best known for making kettles and toasters. Morphy
Richards engineers would not have the first idea about radio reception
issues.
Can't be bothered going round in your little circles.
Boltar
No it doesn't. I used to have a radio that did exactly the same. The
hiss isn't part of the stereo signal as you assume, its electronic
noise created in the receiver when the received stereo difference
signal power isn't very good. The L+R channel noise are not exactly
duplicates 180 degrees out of phase so when you add the L+R channels
back together you just get 2 channels of random noise summed.
B2003
DAB sounds worse than FM
> On Apr 23, 5:46 pm, jamie_...@excite.com wrote:
>> On Apr 23, 9:48 am, "DAB sounds worse than FM" <dab.is@dead> wrote:
>>
>>> From memory, it defaulted to stereo reception on FM even though
>>> it's only got one speaker, so I had to change the settings to make
>>> it default to mono because with stereo it was a bit hissy.
>>
>> Again Steve demonstrates his total lack of cluefulness. The mono
>> speaker carries L+R combined, and when the two channels are combined
>> all the FM stereo hiss disappears and switching the actual tuner to
>> mono would make no difference.
Jamie, as I wrote above, and which you're implying was wrong, the radio
defaulted to stereo reception, and when I changed it to default to mono
reception the hiss disappeared. The radio will have been using a standard
Radioscape DAB/DRM/FM receiver module, and whoever set the defaults up
incorrectly set it to stereo on FM, when it should have been mono on the
basis that the radio only has one speaker and mono reception requires a
lower SNR than is required for stereo.
> No it doesn't. I used to have a radio that did exactly the same. The
> hiss isn't part of the stereo signal as you assume, its electronic
> noise created in the receiver when the received stereo difference
> signal power isn't very good. The L+R channel noise are not exactly
> duplicates 180 degrees out of phase so when you add the L+R channels
> back together you just get 2 channels of random noise summed.
No, whether it's in or out of phase has got nothing to do with you hearing
hiss when you put the switch to stereo and the hiss goes when you switch to
mono.
Say the amplitude on the left signal is 5.0 and the amplitude on the right
channel signal is 4.5 at an instant in time.
An FM signal is split as follows:
Mono = L+R = 5 + 4.5 = 9.5
Difference signal for stereo* = L-R = 5.0 - 4.5 = 0.5
Thermal noise, which is the noise due to the RF front-end in the receiver,
will be flat, so the SNR for the L+R is far higher than the SNR for L-R:
Difference in SNR (dB) = 10 log10 ((L+R) / (L-R)) = 10 log10 (9/0.5) = 12.6
dB
i.e. the SNR for mono is far higher than the SNR for stereo, hence changing
from stereo to mono will very likely eliminate hiss on stations that are a
bit hissy on stereo.
* equations for reproducing L and R signals from sum and difference signals
are:
Left = 0.5 * ((L+R) + (L-R)) = 0.5 * 2L = L
Right = 0.5 * ((L+R) - (L-R)) = 0.5 * 2R = R
Boltar
> > No it doesn't. I used to have a radio that did exactly the same. The
> > hiss isn't part of the stereo signal as you assume, its electronic
> > noise created in the receiver when the received stereo difference
> > signal power isn't very good. The L+R channel noise are not exactly
> > duplicates 180 degrees out of phase so when you add the L+R channels
> > back together you just get 2 channels of random noise summed.
>
> No, whether it's in or out of phase has got nothing to do with you hearing
> hiss when you put the switch to stereo and the hiss goes when you switch to
> mono.
When you switch to mono on a normal radio it should bypass the stereo
decoder and just play the mono signal so any stereo hiss won't come
into it.
> i.e. the SNR for mono is far higher than the SNR for stereo, hence changing
> from stereo to mono will very likely eliminate hiss on stations that are a
> bit hissy on stereo.
Agreed , but if you have a radio that always decodes stereo no matter
what mode its in , but for mono mode literally just feeds the 2 stereo
channels into one speaker then I think you'll still hear the stereo
hiss.
B2003
DAB sounds worse than FM
> On Apr 24, 1:45 pm, "DAB sounds worse than FM" <dab.is@dead> wrote:
>>> No it doesn't. I used to have a radio that did exactly the same. The
>>> hiss isn't part of the stereo signal as you assume, its electronic
>>> noise created in the receiver when the received stereo difference
>>> signal power isn't very good. The L+R channel noise are not exactly
>>> duplicates 180 degrees out of phase so when you add the L+R channels
>>> back together you just get 2 channels of random noise summed.
>>
>> No, whether it's in or out of phase has got nothing to do with you
>> hearing hiss when you put the switch to stereo and the hiss goes
>> when you switch to mono.
>
> When you switch to mono on a normal radio it should bypass the stereo
> decoder and just play the mono signal so any stereo hiss won't come
> into it.
Thanks for telling me something I already knew.
>> i.e. the SNR for mono is far higher than the SNR for stereo, hence
>> changing from stereo to mono will very likely eliminate hiss on
>> stations that are a bit hissy on stereo.
>
> Agreed , but if you have a radio that always decodes stereo no matter
> what mode its in , but for mono mode literally just feeds the 2 stereo
> channels into one speaker then I think you'll still hear the stereo
> hiss.
I haven't suggested otherwise.
jami...@excite.com
> No it doesn't. I used to have a radio that did exactly the same. The
> hiss isn't part of the stereo signal as you assume,
You're assuming that I assume that. I don't.
> its electronic
> noise created in the receiver when the received stereo difference
> signal power isn't very good.
When the received signal strength of the FM carrier isn't very good.
> The L+R channel noise are not exactly
> duplicates 180 degrees out of phase so when you add the L+R channels
> back together you just get 2 channels of random noise summed.
They are exact duplicates because they're both derived from the same
AM subcarrier demodulator. I've just tested this with a weak FM signal
on my hi-fi tuner and regardless of whether I switch the amplifier to
mono, or the FM tuner to mono, or both, the result is the same - the
hiss disappears.
Kristoff Bonne
DAB sounds worse than FM schreef:
>> You are giving the opportunity to play around with a new piece of
>> broadcasting-technology and write an "expert opinion" about it
>> afterwards.
> And that's what I did.
So much for the value of "expert opinion".
:-)
Cheerio! Kr. Bonne.
Kristoff Bonne
Boltar schreef:
> Agreed , but if you have a radio that always decodes stereo no matter
> what mode its in , but for mono mode literally just feeds the 2 stereo
> channels into one speaker then I think you'll still hear the stereo
> hiss.
Do these kind of radios exist?
Anycase, people in these NGs can make things all very difficult, can't they?
Let's ask the question otherwize:
- why is it possible to decode a AMSS signal from a AM-station which is
hardly hearable?
- what do hams use to decode very weak CW or PSK signals?
> B2003
Cheerio! Kr. Bonne.
DAB sounds worse than FM
No, it's still an "expert opinion", but the readers of the magazine simply
aren't interested in DXing anoraky stuff.
As I said, I had 900 words (that's about 1 and 1/3rd pages of 12-point text
in a Word doc) in which I have to describe the radio itself, how easy it is
to use, the features it provides, the reception quality on each band, and
the sound quality on each band, and in the case of this Morphy Richard I
think it also had the EPG and you coudl record and playback from an SD card.
The number of words I could write on DRM was minimal because this radio
supported shitloads of features all of which needed to be mentioned, and yet
you seem to think that the review should have gone into details about AMSS
and all sorts of DRM bullshit that would first need to be explained to
non-anoraks.
I suggest you actually try writing a review that you have to fit into the
900 words of space available before you slag off what I write in mine. The
biggest challenge for me when writing articles is that you have to fit
everythign into a small number of words and you still have to make it
readable / make it flow and you still have to explain things that readers
may not understand because they're not technical. It's not as easy as you
think it is.
FYI: the above 3 paragraphs I've just written consist of 239 words, so I get
a little over 3 times as much to describe everything about the radio - and
in this case I had to introduce DRM because the vast majority of readers
wouldn't even have heard of it! And you're expecting me to write chapter and
verse about irrelevant interference issues? Yeah, right.
Boltar
> On Apr 24, 12:52 pm, Boltar <boltar2...@yahoo.co.uk> wrote:
>
> > No it doesn't. I used to have a radio that did exactly the same. The
> > hiss isn't part of the stereo signal as you assume,
>
> You're assuming that I assume that. I don't.
>
> > its electronic
> > noise created in the receiver when the received stereo difference
> > signal power isn't very good.
>
> When the received signal strength of the FM carrier isn't very good.
Its quite possible to receive a perfectly good mono signal but a lousy
stereo signal. So "not very good" is all a bit relative.
> mono, or the FM tuner to mono, or both, the result is the same - the
> hiss disappears.
Well , not on my setup it doesn't.
B2003
Richard Evans
That may well be true in theory, and may well be true of a reasonable
quality hi-fi tuner. In the past I observed the same thing from my hi-fi
tuner.
However just because it works with a hi-fi tuner, you can't really
assume that the same would be true of a relatively cheap radio. The
cheaper radio may do things to a lower standard, so the stereo noise
might not stay equal and opposite, there may also be other sources of
noise in a cheaper radio.
For what it's worth I was a bit surprised that switching to mono made
such a big difference, on a radio that has only one speaker. Apparently
though that is what happened, and I'm not about to argue that something
that actually happened, did not happen, just because I have some theory
which suggests that it shouldn't happen.
In theory stereo noise ought to cancel out, but does that necessarily
still work for a radio which does things to a lower standard.
Richard E.
Richard Evans
Did you realize that there are actually two different ways to decode a
stereo FM signal.
One method is to decode the subcarrier to get the L-R signal, to combine
with the mono to recreate the stereo.
The other method is a multiplexing method, where the signal is fed to
the left channel for a moment, then to the right for a moment, then back
to the left and so on.
Believe it or not, both methods can correctly decode a stereo FM signal.
As far as I understand it many receivers use the multiplex method,
because it is a cheaper way of doing it. If his method is used then I
would think that timing would be crucial, and some receivers might do
this better than others, which could make a big difference to the
results, and I would imagine that it would affect the ability of the
noise in Left and Right to cancel out, when added together.
Richard E.
jami...@excite.com
wrote:
I don't see why it should. Both methods perform the exact same task
and consequently 'the same thing gets done to' the hiss.
The only cause I can think of would be if one channel was slightly
louder than the other due to an unrelated fault in the radio post-
stereo-decoding.
Richard Evans
I don't know a great deal about it either, but that was the result that
Steve got with the Morphy Richards radio, so there must be a reason for
it. I'm speculating as to what the cause might be, but my main point is
that the MR is not a hi-fi tuner, and wouldn't necessarily work in the
same way, and to the same standards, hence the results may be different.
Richard E.
jami...@excite.com
wrote:
> jamie_...@excite.com wrote:
>
> > I don't see why it should. Both methods perform the exact same task
> > and consequently 'the same thing gets done to' the hiss.
> > The only cause I can think of would be if one channel was slightly
> > louder than the other due to an unrelated fault in the radio post-
> > stereo-decoding.
>
> I don't know a great deal about it either, but that was the result that
> Steve got with the Morphy Richards radio, so there must be a reason for
> it. I'm speculating as to what the cause might be, but my main point is
> that the MR is not a hi-fi tuner, and wouldn't necessarily work in the
> same way, and to the same standards, hence the results may be different.
Steve's an obsessive idiot with an ego problem. You should take his
words with a pinch of salt.
The simple fact is that hiss from decoded FM stereo is always 180
degrees out of phase and will, therefore, always cancel itself out
when the left and right channels are combined.
Richard Evans
>
> Steve's an obsessive idiot with an ego problem. You should take his
> words with a pinch of salt.
> The simple fact is that hiss from decoded FM stereo is always 180
> degrees out of phase and will, therefore, always cancel itself out
> when the left and right channels are combined.
Well we will have to agree to differ.
What you say in true in theory, but I'm not convinced that it always has
to work in practice.
Richard E.
DAB sounds worse than FM
I haven't read all of the posts in this sub-thread, and I've only read
Jamie's comments where you've included the quotes in your reply, but here's
how I see the noise issue, and it won't cancel:
The L+R signal is at baseband. The L-R signal is upconverted to be centred
at 38 kHz, so the noise on the (L+R) and downconverted (L-R) signals is
different, so the stereo channels would be reconstructed as follows (N1 is
the noise on the L+R signal and N2 is the noise on the L-R signal):
Left = 0.5 [(L+R+N1) + (L-R+N2)] = 0.5 x (2L + N1 + N2) = L + (N1 + N2)/2
Left = 0.5 [(L+R+N1) - (L-R+N2)] = 0.5 x (2R + N1 - N2) = L + (N1 - N2)/2
But (N1 - N2) won't reduce the noise level because noise is a zero mean
random process, so there's just as much probability of both N1 and N2 being
negative as there is of them being positive.
DAB sounds worse than FM
> Left = 0.5 [(L+R+N1) + (L-R+N2)] = 0.5 x (2L + N1 + N2) = L + (N1 +
> N2)/2
> Left = 0.5 [(L+R+N1) - (L-R+N2)] = 0.5 x (2R + N1 - N2) = L + (N1 -
> N2)/2
The 2nd equation should be "Right", not Left.
jami...@excite.com
> Richard Evans wrote:
> > jamie_...@excite.com wrote:
>
> >> Steve's an obsessive idiot with an ego problem. You should take his
> >> words with a pinch of salt.
> >> The simple fact is that hiss from decoded FM stereo is always 180
> >> degrees out of phase and will, therefore, always cancel itself out
> >> when the left and right channels are combined.
>
> > Well we will have to agree to differ.
>
> > What you say in true in theory, but I'm not convinced that it always
> > has to work in practice.
>
> I haven't read all of the posts in this sub-thread, and I've only read
> Jamie's comments where you've included the quotes in your reply, but here's
> how I see the noise issue, and it won't cancel:
>
> The L+R signal is at baseband. The L-R signal is upconverted to be centred
> at 38 kHz, so the noise on the (L+R) and downconverted (L-R) signals is
> different, so the stereo channels would be reconstructed as follows (N1 is
> the noise on the L+R signal and N2 is the noise on the L-R signal):
>
> Left = 0.5 [(L+R+N1) + (L-R+N2)] = 0.5 x (2L + N1 + N2) = L + (N1 + N2)/2
>
> Left = 0.5 [(L+R+N1) - (L-R+N2)] = 0.5 x (2R + N1 - N2) = L + (N1 - N2)/2
>
> But (N1 - N2) won't reduce the noise level because noise is a zero mean
> random process, so there's just as much probability of both N1 and N2 being
> negative as there is of them being positive.
N1 is unwanted noise on L+R which would be present regardless of
whether you're listening in stereo or mono.
N2 is unwanted noise derived from the demodulated L-R 'difference
signal' subcarrier.
In the left channel, we are just adding L+R and L-R together, so in
terms of noise in the left channel we have N1 + N2.
In the right channel, we are subtracting L-R from L+R (subtracting
basically means inverting L-R and then adding it to L+R). So in terms
of noise in the right channel we have N1 - N2.
So if we switch the FM radio to stereo and then recombine its output
to mono, in terms of noise we get (N1 + N2 - N2) = N1 hence no FM
stereo hiss.
Richard Evans
>
>
> I haven't read all of the posts in this sub-thread, and I've only read
> Jamie's comments where you've included the quotes in your reply, but here's
> how I see the noise issue, and it won't cancel:
>
> The L+R signal is at baseband. The L-R signal is upconverted to be centred
> at 38 kHz, so the noise on the (L+R) and downconverted (L-R) signals is
> different, so the stereo channels would be reconstructed as follows (N1 is
> the noise on the L+R signal and N2 is the noise on the L-R signal):
>
> Left = 0.5 [(L+R+N1) + (L-R+N2)] = 0.5 x (2L + N1 + N2) = L + (N1 + N2)/2
>
> Left = 0.5 [(L+R+N1) - (L-R+N2)] = 0.5 x (2R + N1 - N2) = L + (N1 - N2)/2
>
> But (N1 - N2) won't reduce the noise level because noise is a zero mean
> random process, so there's just as much probability of both N1 and N2 being
> negative as there is of them being positive.
Hummm. Well in theory I don't quite agree that N2 would not cancel.
I agree in theory with Jamie's point that N2 is derived from exactly the
same source, the stereo sub carrier. Therefore the N2 noise component in
each channel, coming from exactly the same source, should be exactly
equal and opposite. The fact that it is random, should be irrelevant,
because it should in theory be exactly the same for each channel. Two
things that are the same, are the same, regardless of whether their
identical source was a random source. Therefore adding the channels
together should cancel out N2.
However I'm trying to point out that what works in theory, doesn't
always work in practice. I'm not sure exactly what could happen to stop
this theory from becoming reality, but have been speculation on a few
possibilities.
Perhaps in a cheaper radio, the version of L-R used for the left channel
is not actually identical to the one used for the right. In theory they
should be identical, but are they in reality?
An other idea, if the radio doesn't work that way, but uses the
multiplexing method, then L-R doesn't actually come into it. In theory
the multiplexing method should generate the same results as decoding the
stereo sub carrier. In practice, however perhaps this is not true in an
imperfect receiver. Perhaps if the timing of the multiplexing is not
perfect, then some other effect is preventing N2 from cancelling.
I'm not sure exactly how you got the result you got, where a radio with
one speaker produced more noise when in stereo mode. In theory I don't
think that should happen, however I assume that you have no reason to
lie about it, so there must be some reason why that happened. To me the
best explanation seems to be that the theory doesn't necessarily work in
an imperfect receiver.
Richard E.
DAB sounds worse than FM
> DAB sounds worse than FM wrote:
>
>>
>>
>> I haven't read all of the posts in this sub-thread, and I've only
>> read Jamie's comments where you've included the quotes in your
>> reply, but here's how I see the noise issue, and it won't cancel:
>>
>> The L+R signal is at baseband. The L-R signal is upconverted to be
>> centred at 38 kHz, so the noise on the (L+R) and downconverted (L-R)
>> signals is different, so the stereo channels would be reconstructed
>> as follows (N1 is the noise on the L+R signal and N2 is the noise on
>> the L-R signal): Left = 0.5 [(L+R+N1) + (L-R+N2)] = 0.5 x (2L + N1 + N2)
>> = L + (N1 +
>> N2)/2 Left = 0.5 [(L+R+N1) - (L-R+N2)] = 0.5 x (2R + N1 - N2) = L + (N1 -
>> N2)/2 But (N1 - N2) won't reduce the noise level because noise is a zero
>> mean random process, so there's just as much probability of both N1
>> and N2 being negative as there is of them being positive.
>
> Hummm. Well in theory I don't quite agree that N2 would not cancel.
>
> I agree in theory with Jamie's point that N2 is derived from exactly
> the same source, the stereo sub carrier. Therefore the N2 noise
> component in each channel, coming from exactly the same source,
> should be exactly equal and opposite. The fact that it is random,
> should be irrelevant, because it should in theory be exactly the same
> for each channel. Two things that are the same, are the same,
> regardless of whether their identical source was a random source.
> Therefore adding the channels together should cancel out N2.
You've got L+R situated at baseband, and you'ev got L-R centred on 38 kHz.
The noise is AWGN (additive white Gaussian noise) which is flat across the
whole bandwidth, and this noise signal is what's added to the L+R signal.
But in order to add and subtract L-R with L+R you first need to bandpass
filter L-R then downconvert it. Bandpass filterign L-R also bandpass filters
the noise, and downconverting also downconverts the noise with L-R.
N1 is different from N2 - if you bandpass filtered some white noise it is
not the same as the noise that was originally filtered. The power of a noise
signal is N0 x B, where N0 is the spectral amplitude in V^2/Hz and B is the
bandwidth. So a noise signal with a bandwidth 10 times wider than another
noise signal is going to have different power so it obviously couldn't be
the same signal.
> I'm not sure exactly how you got the result you got, where a radio
> with one speaker produced more noise when in stereo mode.
Because the DAB/DRM/FM receiver module was set by default to receive in
stereo - and the module was using software-defined radio, not analogue.
> In theory I
> don't think that should happen, however I assume that you have no
> reason to lie about it, so there must be some reason why that
> happened. To me the best explanation seems to be that the theory
> doesn't necessarily work in an imperfect receiver.
It's just a stereo signal being sent to one speaker.
Kristoff Bonne
DAB sounds worse than FM schreef:
>>>> You are giving the opportunity to play around with a new piece of
>>>> broadcasting-technology and write an "expert opinion" about it
>>>> afterwards.
>>> And that's what I did.
>> So much for the value of "expert opinion".
> No, it's still an "expert opinion", but the readers of the magazine simply
(...)
Hey, I didn't really ask for a public excuse. This was just a remark to
end the discussion with a light note! :-)
Cheerio! Kr. Bonne.
jami...@excite.com
Steve obviously has *no* idea how this works. He doesn't even seem to
realise that the L-R is an AM subcarrier.
Perhaps somebody would care to enlighten him by quoting my previous
post which explains how 'N2' gets cancelled out when reproduced in
mono, since I'm allegedly on his killfile.
DAB sounds worse than FM
You were in my killfile but I've just taken you out, because I kept on
seeing you saying in replies that Richard was posting "Steve doesn't have a
clue about this" or "Steve doesn't have a clue about that" like the fucking
child that you are.
Sorry Jamie, it's you that hasn't got a fucking clue what you're on about.
I OBVIOUSLY KNEW that the L-R is on a subcarrier - read how many times I
said it's centred on 38 kHz - why else would I say that??
And as for N2 being cancelled, how do you propose it would be cancelled?
You're wrong. You're trying to suggest that a wider bandwidth noise signal
could cancel a narrower bandwidth noise signal. How the fuck would that work
then?
DAB sounds worse than FM
Here's a way that might convince you that you're wrong: the FFT is a linear
operation, so if you took the FFT of two noise signals with different
spectra, if they were equal you should be able to subtract the two spectral
representations and have a result of zero across the whole spectrum. But as
the noise spectra are different, if you subtracted one from teh other you
obviously wouldn't get zero, hence the two signals cannot be the same.
jami...@excite.com
> DAB sounds worse than FM wrote:
>
> > And as for N2 being cancelled, how do you propose it would be
> > cancelled? You're wrong. You're trying to suggest that a wider
> > bandwidth noise signal could cancel a narrower bandwidth noise
> > signal. How the fuck would that work then?
>
> Here's a way that might convince you that you're wrong: the FFT is a linear
> operation, so if you took the FFT of two noise signals with different
> spectra, if they were equal you should be able to subtract the two spectral
> representations and have a result of zero across the whole spectrum. But as
> the noise spectra are different, if you subtracted one from teh other you
> obviously wouldn't get zero, hence the two signals cannot be the same.
You don't appear to understand what I or the others in this thread are
saying.
You originally said that FM-stereo noise (N2) was still audible when
listening to the output of an FM stereo tuner on a single mono speaker
carrying L+R channels combined, and that switching the FM tuner to
mono mode would remove or reduce this hiss, and therefore the tuner
should have been set to FM mono mode by default.
We're not talking about hiss which may be audible on the FM carrier
when listening in mono mode (N1). That doesn't come into it at all.
Allow me to reiterate:
N1 is unwanted audible noise on L+R which would be present regardless
Richard Evans
>
>
> You've got L+R situated at baseband, and you'ev got L-R centred on 38 kHz.
> The noise is AWGN (additive white Gaussian noise) which is flat across the
> whole bandwidth, and this noise signal is what's added to the L+R signal.
> But in order to add and subtract L-R with L+R you first need to bandpass
> filter L-R then downconvert it. Bandpass filterign L-R also bandpass filters
> the noise, and downconverting also downconverts the noise with L-R.
>
> N1 is different from N2 - if you bandpass filtered some white noise it is
> not the same as the noise that was originally filtered. The power of a noise
> signal is N0 x B, where N0 is the spectral amplitude in V^2/Hz and B is the
> bandwidth. So a noise signal with a bandwidth 10 times wider than another
> noise signal is going to have different power so it obviously couldn't be
> the same signal.
OK I don't quite understand your maths, but I think there is a slight
misunderstanding here.
I'm not saying that the noise in the L-R channel is the same as the
noise in the L+R channel, obviously those two noise sources would be
different. I'm saying that the noise in the L-R channel is the same as
the noise in the L-R channel. Basically the signal that is added to the
left channel should be exactly the same as the signal that is subtracted
from the right channel. (Unless the receiver is no a perfect receiver).
It is basically two copies of the same thing, one of which is inverted.
So if at some point later on the left and right are added together,
these two would cancel out. The noise generated in the L-R signal should
also end up being identical and opposite when gets into the left and
right channels, because it is two copies of the same thing. The contents
of the L-R channel, and the way it is generated, would make no
difference if it is later cancelled out by adding left and right together.
So basically when you add left and right together, it ought to cancel
out anything that was in L-R, which would be both the stereo image and
the stereo noise.
>
>
>> I'm not sure exactly how you got the result you got, where a radio
>> with one speaker produced more noise when in stereo mode.
>
>
> Because the DAB/DRM/FM receiver module was set by default to receive in
> stereo - and the module was using software-defined radio, not analogue.
Right, so perhaps it is due to it being a software defined radio, and
perhaps it is not a perfectly defined software radio, so perhaps some
imperfect feature of the radio stops the L-R noise from cancelling out
as I described above.
BTW. this is not just a theory. In the past I've also found it worked in
practice, and more than once. For example my first stereo radio was a
stereo radio cassette, which didn't have a mono FM mode, only stereo. I
did however end up connecting it to an amplifier, which did have a mono
button. I often used to tune into quite distant FM signals, which often
resulted in stereo noise, but if the noise started to annoy me, I'd just
press the mono button on the amplifier, and all the stereo noise
disappeared.
If the Morphy Richards radio doesn't behave in this way, then there must
be something different about the way it works, which might perhaps be
that it is just not a very good implementation of an FM Radio.
Richard E.
DAB sounds worse than FM
> On Apr 25, 10:36 pm, "DAB sounds worse than FM" <dab.is@dead> wrote:
>> DAB sounds worse than FM wrote:
>>
>>> And as for N2 being cancelled, how do you propose it would be
>>> cancelled? You're wrong. You're trying to suggest that a wider
>>> bandwidth noise signal could cancel a narrower bandwidth noise
>>> signal. How the fuck would that work then?
>>
>> Here's a way that might convince you that you're wrong: the FFT is a
>> linear operation, so if you took the FFT of two noise signals with
>> different spectra, if they were equal you should be able to subtract
>> the two spectral representations and have a result of zero across
>> the whole spectrum. But as the noise spectra are different, if you
>> subtracted one from teh other you obviously wouldn't get zero, hence
>> the two signals cannot be the same.
>
> You don't appear to understand what I or the others in this thread are
> saying.
> You originally said that FM-stereo noise (N2)
N2 is the noise on the L-R signal, and FM stereo channel reconstruction is
given by these equations (N1 is the noise on the L+R signal):
Left = 0.5 [(L+R+N1) + (L-R+N2)] = 0.5 x (2L + N1 + N2)
Left = L + (N1 + N2)/2
Right = 0.5 [(L+R+N1) - (L-R+N2)] = 0.5 x (2R + N1 - N2)
Right = R + (N1 - N2)/2
> was still audible when
> listening to the output of an FM stereo tuner on a single mono speaker
> carrying L+R channels combined,
No, when the setting was stereo it wasn't carrying the combined L+R signal -
that's the whole point, and there's nothing surprising about what I was
hearing.
The device was a Morphy Richards 27024 DAB/DRM/FM/MW/etc portable radio that
only has one speaker, and the receiver module, which uses software-defined
radio (i.e. the radio is demodulated etc in software, not hardware, apart
from the RF front-end doing the downconversion to IF), was set to stereo in
the settings on the radio. So the software was doing all the processing for
stereo, and then the output audio signal will simply have been one channel
of the "stereo" signal. The Roberts RD20 was also incorrectly defaulting to
stereo, and this was also using one of Radioscape's new (at the time)
receiver modules.
Radioscape won't make separate receiver modules for 1 and 2 speaker radios.
They will make one module that can be used for both, and the manufacturers
will just have to connect the single speaker to one of the pins on the
module.
So when you say I was still hearing hiss when listening to L+R mono, that's
not what I said, and that's not what I was listening to. I was listening to
the stereo reconstruction of one of the two channels.
> and that switching the FM tuner to
> mono mode would remove or reduce this hiss, and therefore the tuner
> should have been set to FM mono mode by default.
This bit is right.
> We're not talking about hiss which may be audible on the FM carrier
> when listening in mono mode (N1). That doesn't come into it at all.
>
> Allow me to reiterate:
> N1 is unwanted audible noise on L+R which would be present regardless
> of whether you're listening in stereo or mono.
> N2 is unwanted noise derived from the demodulated L-R 'difference
> signal' subcarrier.
> In the left channel, we are just adding L+R and L-R together, so in
> terms of noise in the left channel we have N1 + N2.
> In the right channel, we are subtracting L-R from L+R (subtracting
> basically means inverting L-R and then adding it to L+R). So in terms
> of noise in the right channel we have N1 - N2.
Correct.
> So if we switch the FM radio to stereo and then recombine its output
> to mono, in terms of noise we get (N1 + N2 - N2) = N1 hence no FM
> stereo hiss.
No. N2 is not "stereo hiss". N2 is the noise on the L-R channel. Stereo hiss
is all to do with the fact that the SNR is lower. Here's what I wrote in
reply to Boltar about this:
"Say the amplitude on the left signal is 5.0 and the amplitude on the right
channel signal is 4.5 at an instant in time.
An FM signal is split as follows:
Mono = L+R = 5 + 4.5 = 9.5
Difference signal for stereo = L-R = 5.0 - 4.5 = 0.5
Thermal noise, which is the noise due to the RF front-end in the receiver,
will be flat, so the SNR for the L+R is far higher than the SNR for L-R:
Difference in SNR (dB) = 10 log10 ((L+R) / (L-R)) = 10 log10 (9/0.5) = 12.6
dB
i.e. the SNR for mono is far higher than the SNR for stereo, hence changing
from stereo to mono will very likely eliminate hiss on stations that are a
bit hissy on stereo."
jami...@excite.com
<snip>
> > was still audible when
> > listening to the output of an FM stereo tuner on a single mono speaker
> > carrying L+R channels combined,
>
> No, when the setting was stereo it wasn't carrying the combined L+R signal -
> that's the whole point, and there's nothing surprising about what I was
> hearing...
<snip>
> ...the output audio signal will simply have been one channel of the "stereo"
> signal...
<snip>
> ...the manufacturers will just have to connect the single speaker to one of the
> pins on the module...
Bollocks. Internal mono speakers *always* carry L+R combined. You know
this of course, and you're just trying to hide the fact that you
didn't understand how FM stereo works until we told you.
Richard Evans
So do people *always* remember to fuel in their cars
do boats *always* float
does the mains power *always* stay on.
I think the word you should have used is "usually".
Yes when listening through one mono speaker you ought to get L+R, but
then again things don't *always* happen as they ought to.
As I have been saying all along, I agree with your theory that adding
left and right channels together should cancel out the stereo noise, but
this doesn't always follow in reality, and it is probably down to
something happening in this particular radio. Now I know what that
something is, it is not generating real mono sound.
Perhaps they thought it might save them a few pennies by not bothering
to combine both the channels together, or then again perhaps they simply
screwed up.
Richard E.
Richard Evans
>
> If the Morphy Richards radio doesn't behave in this way, then there must
> be something different about the way it works, which might perhaps be
> that it is just not a very good implementation of an FM Radio.
>
> Richard E.
I just read another of your posts. So it seems that it is something
different about this radio. It wasn't actually reproducing mono, but
just one of the stereo channels.
Perhaps this is something that you mentioned in an earlier post that I
didn't spot.
Richard E.
hwh
> Perhaps they thought it might save them a few pennies by not bothering
> to combine both the channels together, or then again perhaps they simply
> screwed up.
Easily achieved by connecting one of the channels out-of-phase.
gr, hwh
jami...@excite.com
wrote:
> *always*???
>
> So do people *always* remember to fuel in their cars
> do boats *always* float
> does the mains power *always* stay on.
>
> I think the word you should have used is "usually".
> Yes when listening through one mono speaker you ought to get L+R, but
> then again things don't *always* happen as they ought to.
>
> As I have been saying all along, I agree with your theory that adding
> left and right channels together should cancel out the stereo noise, but
> this doesn't always follow in reality, and it is probably down to
> something happening in this particular radio. Now I know what that
> something is, it is not generating real mono sound.
>
> Perhaps they thought it might save them a few pennies by not bothering
> to combine both the channels together, or then again perhaps they simply
> screwed up.
He's supposed to have "reviewed" this radio for a magazine or
something.
If the mono speaker was only carrying one stereo channel, then *that*
would have been the criticism he made about the radio. Instead he
criticised the fact that its FM tuner defaulted to stereo.
So what's more likely?
1) He thinks that it doesn't matter if people only hear one of the
stereo channels when listening via the internal speaker and reducing
the background hiss is the only thing they should be worried about.
2) He automatically assumed that "FM tuner in stereo mode = more hiss"
without bothering to compare the two in practice, and without
understanding how FM stereo works, so he's now trying to cover up for
his lack of clue.
DAB sounds worse than FM
> On Apr 26, 9:48 am, "DAB sounds worse than FM" <dab.is@dead> wrote:
>
> <snip>
>
>>> was still audible when
>>> listening to the output of an FM stereo tuner on a single mono
>>> speaker carrying L+R channels combined,
>>
>> No, when the setting was stereo it wasn't carrying the combined L+R
>> signal - that's the whole point, and there's nothing surprising
>> about what I was hearing...
> <snip>
>> ...the output audio signal will simply have been one channel of the
>> "stereo" signal...
> <snip>
>> ...the manufacturers will just have to connect the single speaker to
>> one of the pins on the module...
>
>
> Bollocks. Internal mono speakers *always* carry L+R combined.
DAB portable radios use receiver modules, and Frontier-Silicon produces 80%
of all the DAB receiver modules that go inside DAB receivers that are sold
in the UK. Their list of DAB receiver modules is on here:
http://www.frontier-silicon.com/audio/index.htm
Please find me one that only allows mono reception. You won't be able to
find one, because they will all do both mono and stereo.
The same DAB receiver modules are used inside single-speaker and two-speaker
portable radios, hi-fi tuners, clock radios, you name it. They all support
both mono and stereo. The receiver modules that was inside the Morphy
Richards 27024 was a Radioscape DAB/DRM/FM/AM etc receiver module -
Radioscape is the other DAB receiver module company, and it produces the
majority of the remaining 20% of DAB receiver modules.
In the settings of the Morphy Ricahrds 27024 it was set to "stereo", not
mono. These receiver modules are implemented using software-defined radio,
so if the radio is set to stereo the software will do the necessary
processing to form the stereo signal, and the L and R signals will be sent
to the appropriate pins on the receiver module so that they can be amplified
and sent to the speaker. For single-speaker DAB portable radios they'll only
connect to one of the pins, obviously.
When I changed the setting from stereo to mono, the hiss went, just as it
does on hi-fi tuners or on other DAB portable radios that can be switched
between mono and stereo.
> You know
> this of course, and you're just trying to hide the fact that you
> didn't understand how FM stereo works until we told you.
STFU.
DAB sounds worse than FM
Correct. This was simply an error made when the radios were produced.
DAB sounds worse than FM
> On Apr 26, 12:07 pm, Richard Evans <R.P.Evans.NoS...@NTLWorld.com>
> wrote:
>
>> *always*???
>>
>> So do people *always* remember to fuel in their cars
>> do boats *always* float
>> does the mains power *always* stay on.
>>
>> I think the word you should have used is "usually".
>> Yes when listening through one mono speaker you ought to get L+R, but
>> then again things don't *always* happen as they ought to.
>>
>> As I have been saying all along, I agree with your theory that adding
>> left and right channels together should cancel out the stereo noise,
>> but this doesn't always follow in reality, and it is probably down
>> to something happening in this particular radio. Now I know what that
>> something is, it is not generating real mono sound.
>>
>> Perhaps they thought it might save them a few pennies by not
>> bothering to combine both the channels together, or then again
>> perhaps they simply screwed up.
>
> He's supposed to have "reviewed" this radio for a magazine or
> something.
> If the mono speaker was only carrying one stereo channel, then *that*
> would have been the criticism he made about the radio. Instead he
> criticised the fact that its FM tuner defaulted to stereo.
The reception quality was poor, but when I changed it to mono it became
better.
> So what's more likely?
> 1) He thinks that it doesn't matter if people only hear one of the
> stereo channels when listening via the internal speaker and reducing
> the background hiss is the only thing they should be worried about.
> 2) He automatically assumed that "FM tuner in stereo mode = more hiss"
> without bothering to compare the two in practice,
I did compare the two in practice - as soon as I changed the setting from
stereo to mono the hiss disappeared. Which bit of this don't you understand?
> and without
> understanding how FM stereo works, so he's now trying to cover up for
> his lack of clue.
You really are an utter knobhead.
jami...@excite.com
> You really are an utter knobhead.
At least I'm not a clueless, obsessive idiot with delusions of
competence, bad manners and an ego problem.
DAB sounds worse than FM
The only people who doubt my competence are unsurprisingly people who I
don't get on with, such as people like you, so you saying that I lack
competence is oh so going to devastate me.
As for having bad manners, would you suggest that continually calling
someone a clueless, obsessive idiot etc is good manners? Similarly, you seem
to think that you know it all when you actually know fuck all, so you're
hardly one to be accusing other people of having an ego problem.
Put simply: before you go round accusing others of things, try looking at
yourself first.
Malcolm Knight
news:6bf7e8d8-7b22-4abf...@b1g2000hsg.googlegroups.com...
> 2) He automatically assumed that "FM tuner in stereo mode = more hiss"
> without bothering to compare the two in practice, and without
> understanding how FM stereo works, so he's now trying to cover up for
> his lack of clue.
In 1962, before such things could be bought off the shelf, I made my
own FM stereo receiver from individual components both valve and
transistor and in the process had to learn exactly how the system
worked. Naturally I have forgotten most of it in the intervening years
but I have not as yet read anything from Steve I disagree with whereas
my first reaction to your claims is that you were talking out of your
backside.
But then along came Richard Evans and now I am totally confused. However
I have never then (1962) or since read that you could get rid of the
hiss by simply summing together at the audio stage and TBH I cannot see
how that would work, unless some clot has got a channel in anti-phase.
--
Malcolm
Richard Evans
>
> But then along came Richard Evans and now I am totally confused. However
> I have never then (1962) or since read that you could get rid of the
> hiss by simply summing together at the audio stage and TBH I cannot see
> how that would work, unless some clot has got a channel in anti-phase.
But wouldn't the stereo hiss be in anti-phase?
Surely if the L-R is added to one channel, and subtracted from the
other, then any hiss that was in L-R would be equal and opposite.
OK, adding the two output channels together might not technically be
exactly the same as putting the receiver in mono in the first place, but
surely it would at least cancel out most of the noise that was in L-R.
Richard E.
DAB sounds worse than FM
> Malcolm Knight wrote:
>
>>
>> But then along came Richard Evans and now I am totally confused.
>> However I have never then (1962) or since read that you could get
>> rid of the hiss by simply summing together at the audio stage and
>> TBH I cannot see how that would work, unless some clot has got a
>> channel in anti-phase.
>
> But wouldn't the stereo hiss be in anti-phase?
There is no such thing as "stereo hiss" - Jamie seems to have invented that
out of thin air.
The different signals are as follows:
Sum = L+R+N1
Difference L-R+N2
N1 is NOT the same as N2
Left = 0.5 (sum + difference)
Right = 0.5 (sum - difference)
Left = 0.5 [(L+R+N1) + (L-R+N2)] = L + (N1 + N2)/2
Right = 0.5 [(L+R+N1) - (L-R+N2)] = R + (N1 - N2)/2
> Surely if the L-R is added to one channel, and subtracted from the
> other, then any hiss that was in L-R would be equal and opposite.
If L-R is added to say the left channel then you'd have:
Left = L + L-R = 2L - R
You need to get L with no R left.
> OK, adding the two output channels together might not technically be
> exactly the same as putting the receiver in mono in the first place,
Yes, it is the same.
> but surely it would at least cancel out most of the noise that was in
> L-R.
No, no noise is cancelled.
DAB sounds worse than FM
I haven't read all of their posts, and I haven't read much of Jamie's
because he's been in my killfile for the last few days (I decided to take
him out to keep an eye on him), but if they think they can cancel noise then
they must be doing something wrong.
Richard Evans
>
> But then along came Richard Evans and now I am totally confused. However
> I have never then (1962) or since read that you could get rid of the
> hiss by simply summing together at the audio stage and TBH I cannot see
> how that would work, unless some clot has got a channel in anti-phase.
I thought perhaps I'd better prove the point by some experimentation.
I'm now uploading a compressed folder containing 2 wave files.
StNoise.wav and mono.wav.
Also a simple program I wrote called Wavmono, which basically just
generates a mono wave file by adding together the left and right channels.
StNoise.wav is a sample I recorded from a weak FM station received in
stereo, it sounds rather noisey. I then created mono.wav by using my
executable program. In case you want to try yourself, the command line
was "Wavmono Stnoise mono".
It is very obvious that the stereo version contains far more noise than
the mono version. I don't know what else I can do to illustrate the point.
The download link is
http://www.sendspace.com/file/xyf5jy
Richard E.
Malcolm Knight
news:ywGQj.72764$jH5....@newsfe3-win.ntli.net...
Well looking at it from a purely practical point of view and with a
little historical persepective, stereo hiss was a much talked about
problem when FM stereo was first introduced and I'm sure if summing L/R
audio output was a cure for it the enthusiast home builders would have
incorporated it into our primitive devices instead of more complex
solutions at the front end.
As the L-R (difference channel) is crudely multiplexed on to the carrier
at what is in effect high audio frequencies it's always likely to have
more noise in it than the mono signal. Even if it was at the same level
it wouldn't be related in any way to the L+R such that it could be
cancelled. The only way to lose it is to lose the L-R altogether. ie.
revert to being a mono only receiver. The more I think about it the more
46 years of neglect disappear and the claims become laughable.
--
Malcolm
Richard Evans
>
> I haven't read all of their posts, and I haven't read much of Jamie's
> because he's been in my killfile for the last few days (I decided to take
> him out to keep an eye on him), but if they think they can cancel noise then
> they must be doing something wrong.
>
>
>
Perhaps then you have an explanation for the samples I have just uploaded.
http://www.sendspace.com/file/xyf5jy
Stnoise.wav is a sample I recorded from a weak stereo FM station
mono.wav is a file I then generated using a simple program to add
together the left and right channels from Stnoise.wav.
It is not hard to hear that mono.wav contains far less noise then
Stnoise.wav.
Richard E.
Malcolm Knight
news:5wGQj.72763$jH5....@newsfe3-win.ntli.net...
> Richard Evans wrote:
>> OK, adding the two output channels together might not technically be
>> exactly the same as putting the receiver in mono in the first place,
>
> Yes, it is the same.
>
For clarity, only in the sense that the audio content is the same. The
main reason for using the Zenith GE system was because unlike other
propositions at the time it was thought to be totally compatible with
mono receivers.
>> but surely it would at least cancel out most of the noise that was in
>> L-R.
>
> No, no noise is cancelled.
Two different random noise sources are added together. I suppose a tiny
bit might be randomly cancelled. :-)
--
Malcolm
Richard Evans
> Richard Evans wrote:
>> Malcolm Knight wrote:
>>
>>> But then along came Richard Evans and now I am totally confused.
>>> However I have never then (1962) or since read that you could get
>>> rid of the hiss by simply summing together at the audio stage and
>>> TBH I cannot see how that would work, unless some clot has got a
>>> channel in anti-phase.
>> But wouldn't the stereo hiss be in anti-phase?
>
>
> There is no such thing as "stereo hiss" - Jamie seems to have invented that
> out of thin air.
>
> The different signals are as follows:
>
> Sum = L+R+N1
> Difference L-R+N2
>
> N1 is NOT the same as N2
I have never said that N1 and N2 are the same.
What I'm saying is that the same version of N2 is added to both of the
output channels (but one is inverted). Therefore N2 is equal and
opposite for the two output channels, so if you add them together the
noise N2 should get cancelled.
Obviously N1 would still remain, but removing N2 still reduces the level
of noise.
>
> Left = 0.5 (sum + difference)
> Right = 0.5 (sum - difference)
>
> Left = 0.5 [(L+R+N1) + (L-R+N2)] = L + (N1 + N2)/2
> Right = 0.5 [(L+R+N1) - (L-R+N2)] = R + (N1 - N2)/2
So what do you get when you add the Left and Right channels together.
(L + (N1 + N2)/2) + (R + (N1 - N2)/2).
Doesn't that work out to L + R + N1 ?
doesn't N2 end being cancelled out ?
>
>
>> Surely if the L-R is added to one channel, and subtracted from the
>> other, then any hiss that was in L-R would be equal and opposite.
>
>
> If L-R is added to say the left channel then you'd have:
>
> Left = L + L-R = 2L - R
>
> You need to get L with no R left.
That's not quite what I mean.
Obviously the Left channel is created by adding L-R to L+R,
and the right channel is generated by subtracting L-R from L+R.
But that is not really the point I'm trying to make.
My point is simply that L-R is added to one of the output channels, and
subtracted form the other. If what you are adding to one channel is
identical to what you subtract from the other, then surely L-R is equal
and opposite in the 2 output channels. That includes both the sound
contained in L-R and the noise contained in L-R. So surely adding the
two output channels together, would include adding the positive copy of
L-R to the negative copy of L-R, and the two would cancel, and this
would also cancel the noise that was in L-R.
>
>
>> OK, adding the two output channels together might not technically be
>> exactly the same as putting the receiver in mono in the first place,
>
>
> Yes, it is the same.
>
>
>> but surely it would at least cancel out most of the noise that was in
>> L-R.
>
>
> No, no noise is cancelled.
To me that doesn't make sense, to me it seems to work both in theory and
in practice (assuming that the FM receiver works correctly).
Richard E.
Richard Evans
>
> Two different random noise sources are added together. I suppose a tiny
> bit might be randomly cancelled. :-)
But for the random noise that was in the stereo sub carrier, you are not
just adding two random sources together, you are adding together two
opposite copies of the *same* random source.
Richard E.
jami...@excite.com
> jamie_...@excite.com wrote:
> > On Apr 26, 12:44 pm, "DAB sounds worse than FM" <dab.is@dead> wrote:
>
> >> You really are an utter knobhead.
>
> > At least I'm not a clueless, obsessive idiot with delusions of
> > competence, bad manners and an ego problem.
>
> The only people who doubt my competence are unsurprisingly people who I
> don't get on with, such as people like you, so you saying that I lack
> competence is oh so going to devastate me.
>
> As for having bad manners, would you suggest that continually calling
> someone a clueless, obsessive idiot etc is good manners? Similarly, you seem
> to think that you know it all when you actually know fuck all, so you're
> hardly one to be accusing other people of having an ego problem.
>
> Put simply: before you go round accusing others of things, try looking at
> yourself first.
I'm more polite than you and I know more than you.
Richard Evans
>
> As the L-R (difference channel) is crudely multiplexed on to the carrier
> at what is in effect high audio frequencies it's always likely to have
> more noise in it than the mono signal. Even if it was at the same level
> it wouldn't be related in any way to the L+R such that it could be
> cancelled. The only way to lose it is to lose the L-R altogether. ie.
> revert to being a mono only receiver. The more I think about it the more
> 46 years of neglect disappear and the claims become laughable.
you and Steve seem to be missing the crucial point that I'm trying to make.
I am in no way suggesting that the noise in L+R is the same as the noise
in L-R.
What I am saying is that the same copy of L-R is used for the two output
channels, but inverted in one of the channels. So if you then add the
two output channels together then yes you do loose the L-R channel all
together, and this includes losing the noise that was in L-R, because
that was also identical and opposite for both output channels. So what
you end up with is essentially the same as if you had received the
signal in mono in the first place. Mono sound with the same level of
noise that you would have got if you received in mono.
Richard E.
Malcolm Knight
"Richard Evans" <R.P.Evan...@NTLWorld.com> wrote in message
news:NgHQj.70675$kN5....@newsfe1-gui.ntli.net...
> Malcolm Knight wrote:
>
<snip>
> you and Steve seem to be missing the crucial point that I'm trying to
> make.
Not missing it, but I'm wondering why your simple solution isn't the one
always adopted instead of defeating the stereo decoder which has been
the traditional method since the 1950s. I suspect that this is where a
little knowledge is a dangerous thing. Not that I am in a position to
prove you wrong.
--
Malcolm
jami...@excite.com
trap.co.uk> wrote:
> Not missing it, but I'm wondering why your simple solution isn't the one
> always adopted instead of defeating the stereo decoder which has been
> the traditional method since the 1950s. I suspect that this is where a
> little knowledge is a dangerous thing. Not that I am in a position to
> prove you wrong.
Maybe you should shut up then?
FM Multiplex stereo decoding is all very simple logic - obviously way
over Steve's head, but if it's over yours too then I think you should
stop making a fool of yourself right now.
A very similar method is used on vinyl records incidentally, with the
horizontal groove modulation carrying L+R and an additional vertical
groove modulation carrying L-R.
Richard Evans
Well I don't know how FM receivers actually do it in practice.
However thinking about how it could be done, what would be easier.
Adding the two output channels together, or switching off the L-R
signal. I suspect that the latter option would be slightly easier, and
also slightly more accurate. But then not being an expert in FM
receivers I couldn't say for certain.
Richard E.
DAB sounds worse than FM
Yes, it works out to be L+R+N1. But you've already got L+R+N1, because
that's the "sum" above, and that's what a receiver outputs! K+R+N1 is the
part of the demodulated FM signal sitting at baseband, i.e. sitting there
ready and waiting to be used by simply applying a lowpass filter to the
FM-demodulated signal and outputting that to teh amplifier. This is what
happens when you switch to mono - there's no need to use L-R AT ALL.
Call the sum signal S = L+R, and the difference signal D = L-R. You're
trying to do this:
Left = 0.5 (S + D)
Right = 0.5 (S - D)
then you're doing:
Output = Left + Right
But all you need to do is:
Output = S
S is sitting there ready to be used!! And S = L+R+N1.
>>> but surely it would at least cancel out most of the noise that was
>>> in L-R.
>>
>>
>> No, no noise is cancelled.
>
> To me that doesn't make sense, to me it seems to work both in theory
> and in practice (assuming that the FM receiver works correctly).
Yes, it does work well in practice, and the reason it works in practice is
because the SNR increases:
Mono = L + R + N1
Stereo left = L + (N1 + N2)/2
Stereo right = R + (N1 - N2)/2
Firstly, with the mono signal the wanted signal is L+R whereas for the
stereo channels it's just either L or R, so the wanted signal part is lower
power - if the power in the L and R channels were the same then the power of
the wanted signal increases by 6 dB by adding the two channels together.
Also, the noise power goes up for the stereo signal as well, because when
adding "uncorrelated" random noise signals together (this is additive white
Gaussion noise (AWGN), so it is uncorrelated random noise) you add the means
and you add the "variances" of the two signals - because you have to
describe random signals by their statistics.
For AWGN, the mean is zero, and because the mean is zero the variance also
equals the power, so when adding two equal-power noise signals together you
get another noise signal with twice the power.
So with mono relative to stereo, you get 6 dB higher SNR for the wanted
signal being higher, and you avoid doubling the power of the noise.
If the L and R channels were of equal power, which they probably would be,
the difference in SNR should be about 12 dB, which is a big difference in
SNR, which is why mono sounds much less hissy than stereo.
Malcolm Knight
news:5d25eec0-8f9c-43c6...@w7g2000hsa.googlegroups.com...
> On Apr 26, 4:30 pm, "Malcolm Knight" <firstinitial.secondinit...@spam-
> trap.co.uk> wrote:
>
>> Not missing it, but I'm wondering why your simple solution isn't the
>> one
>> always adopted instead of defeating the stereo decoder which has been
>> the traditional method since the 1950s. I suspect that this is where
>> a
>> little knowledge is a dangerous thing. Not that I am in a position to
>> prove you wrong.
>
> Maybe you should shut up then?
Only when you tell us why early tuner designers didn't come up with the
idea of mixing the L/R audio derived from the decoder instead of taking
the unadulterated mono signal. The multiplexing process must introduce
extra noise so it's counter-intuitive for it to be the ideal solution.
> FM Multiplex stereo decoding is all very simple logic - obviously way
> over Steve's head, but if it's over yours too then I think you should
> stop making a fool of yourself right now.
The only reason you are not in my kill file is that your ignorance is
sometimes amusing and reinforces my view of the current state of the
education system. You discredited yourself when you first appeared on
the scene although I accept your random noise generator has
occasioanally come up with a right answer since.
> A very similar method is used on vinyl records incidentally, with the
> horizontal groove modulation carrying L+R and an additional vertical
> groove modulation carrying L-R.
Yeah, I worked that out and modified a pickup a little more than fifty
years ago. It sum and differenced the vertical L-R signal and the mono
separately rather than take the usual mechanical route of reading the 45
degree groove walls.
I suppose being an obnoxious little school boy is part of the growing up
process. With luck you won't remain a school boy for ever.
--
Malcolm
Mark Carver
What I would say is this:-
Back in 1973 my father had a Tandberg Tuner-Amp (TR-200) and a Tandberg
Cassette Deck (TCR-300 ISTR). The cassette deck was fed from a 5 pin DIN line
socket, that also carried the output back from the cassette deck. The Tuner
Amp had a 'Tape Monitor' button. The purpose of this is was to feed the signal
from the Tuner section, into the tape deck, and loop back out into the Amp's
input.
It gave same degree of confidence that you were actually recoding the tuner
output.
The cassette deck had a 'Mono' button, that summed the L and R inputs on its
line input. Listening to the tuner, via the deck, and depressing this button
on weak stereo reception would increase the signal to noise ratio, to what
*sounded* to be the same level as operating the 'Mono' button of the tuner
(which killed the decoder).
I have no idea what the *measured* difference between the two methods might
have been, but it does prove that summing left and right downstream of the
decoder does improve s/n ratio. Also, that's what car radios do, albeit
'blending' the AF of the two channels as the AGC voltage in the tuner head
decreases.
--
Mark
Please replace invalid and invalid with gmx and net to reply.
Richard Evans
> Richard Evans wrote:
>> So what do you get when you add the Left and Right channels together.
>>
>> (L + (N1 + N2)/2) + (R + (N1 - N2)/2).
>> Doesn't that work out to L + R + N1 ?
>> doesn't N2 end being cancelled out ?
>
>
> Yes, it works out to be L+R+N1. But you've already got L+R+N1, because
> that's the "sum" above, and that's what a receiver outputs! K+R+N1 is the
> part of the demodulated FM signal sitting at baseband, i.e. sitting there
> ready and waiting to be used by simply applying a lowpass filter to the
> FM-demodulated signal and outputting that to teh amplifier. This is what
> happens when you switch to mono - there's no need to use L-R AT ALL.
>
> Call the sum signal S = L+R, and the difference signal D = L-R. You're
> trying to do this:
>
> Left = 0.5 (S + D)
> Right = 0.5 (S - D)
>
> then you're doing:
>
> Output = Left + Right
>
> But all you need to do is:
>
> Output = S
>
> S is sitting there ready to be used!! And S = L+R+N1.
Couldn't agree more.
So what was all the discussion here about, as you seem to have proved
what I have been trying to say all along. That is that adding together
the Left and Right channels from an FM stereo radio achieves the same
result as having the radio receive in mono in the first place.
I think the only reason why we got onto this discussion is that I didn't
realize that the Morphy Richards radio only outputted one of the stereo
channels to the speaker (not the sum of both channels). Therefore it
seemed strange to me that it produced more noise when in stereo mode. If
it had fed it's single speaker with the sum of both Left and Right
channels, then that would have been equivalent to mono reception, and so
I wouldn't have expected any significant increase in noise.
The rest of your post gets a little to technical for me, so I can't
really comment on it.
Richard E.
jami...@excite.com
trap.co.uk> wrote:
>
> Only when you tell us why early tuner designers didn't come up with the
> idea of mixing the L/R audio derived from the decoder instead of taking
> the unadulterated mono signal. The multiplexing process must introduce
> extra noise so it's counter-intuitive for it to be the ideal solution.
The former is more elegant? The latter involves portions of the
electronics being operated needlessly, which is an issue where tubes
are used?
Who knows, and who cares. Facts are facts. The demodulated difference
signal, noise and all, gets added to L+R generate the left channel,
and subtracted from L+R to generate the right channel, leaving you
with the exact same amount of noise added to the left channel as is
subtracted from the right.
I don't know how many times I have to repeat this before you'll accept
it.
<snip your impression of steve>
> > A very similar method is used on vinyl records incidentally, with the
> > horizontal groove modulation carrying L+R and an additional vertical
> > groove modulation carrying L-R.
>
> Yeah, I worked that out and modified a pickup a little more than fifty
> years ago. It sum and differenced the vertical L-R signal and the mono
> separately rather than take the usual mechanical route of reading the 45
> degree groove walls.
And yet you don't understand how FM MPX stereo works.
> I suppose being an obnoxious little school boy is part of the growing up
> process. With luck you won't remain a school boy for ever.
I'm not obnoxious. :p
jami...@excite.com
> On Apr 26, 6:22 pm, "Malcolm Knight" <firstinitial.secondinit...@spam-
>
> trap.co.uk> wrote:
>
> > Only when you tell us why early tuner designers didn't come up with the
> > idea of mixing the L/R audio derived from the decoder instead of taking
> > the unadulterated mono signal. The multiplexing process must introduce
> > extra noise so it's counter-intuitive for it to be the ideal solution.
>
> The former is more elegant? The latter involves portions of the
> electronics being operated needlessly, which is an issue where tubes
> are used?
Correction: 'latter' should say 'former' and vice-versa.
Brian Gregory [UK]
> Oh and one more thing to add.
>
> Did you realize that there are actually two different ways to decode a
> stereo FM signal.
>
> One method is to decode the subcarrier to get the L-R signal, to combine
> with the mono to recreate the stereo.
>
> The other method is a multiplexing method, where the signal is fed to the
> left channel for a moment, then to the right for a moment, then back to
> the left and so on.
I'd be very surprised to find any receiver using anything other than what
you call the multiplexing method.
> Believe it or not, both methods can correctly decode a stereo FM signal.
> As far as I understand it many receivers use the multiplex method, because
> it is a cheaper way of doing it. If his method is used then I would think
> that timing would be crucial, and some receivers might do this better than
> others, which could make a big difference to the results, and I would
> imagine that it would affect the ability of the noise in Left and Right to
> cancel out, when added together.
It's much more likely that the noise will cancel out if the multiplex method
is used. For a start it's much easier to implement precisely. Also even if
the timing is off the noise still cancels out exactly because you are just
switching the signal quickly between two different paths to the summing
circuit that you're hoping will cancel the noise. It doesn't matter what the
timing is -- the noise will cancel out.
If it doesn't cancel in the DRM27024 we can safely assume they are doing
something very stupid.
--
Brian Gregory. (In the UK)
n...@bgdsv.co.uk
To email me remove the letter vee.
Brian Gregory [UK]
> However I'm trying to point out that what works in theory, doesn't always
> work in practice.
How many times have you done it and found it didn't cancel out?
I've done it with at least five different tuners and they all cancelled out
closely enough that there was no audible difference from switching the tuner
to mono.
Something is wrong if they don't cancel at very well.
Brian Gregory [UK]
> Here's a way that might convince you that you're wrong: the FFT is a
> linear operation, so if you took the FFT of two noise signals with
> different spectra, if they were equal you should be able to subtract the
> two spectral representations and have a result of zero across the whole
> spectrum. But as the noise spectra are different, if you subtracted one
> from teh other you obviously wouldn't get zero, hence the two signals
> cannot be the same.
I've respected you as knowledgeable but rather argumentative until now (not
unlike me).
But I'm afraid this makes you look like a total tech moron.
Brian Gregory [UK]
news:48131188$0$14351$e4fe...@news.xs4all.nl...
> Easily achieved by connecting one of the channels out-of-phase.
Maybe but I'll be an utterly crap radio if they have because you won't hear
anything from the centre of the stereo "sound stage" (is that the right
phrase?) at all.
Brian Gregory [UK]
message news:67gosfF...@mid.individual.net...
> In 1962, before such things could be bought off the shelf, I made my own
> FM stereo receiver from individual components both valve and transistor
> and in the process had to learn exactly how the system worked. Naturally I
> have forgotten most of it in the intervening years but I have not as yet
> read anything from Steve I disagree with whereas my first reaction to your
> claims is that you were talking out of your backside.
>
> But then along came Richard Evans and now I am totally confused. However I
> have never then (1962) or since read that you could get rid of the hiss by
> simply summing together at the audio stage and TBH I cannot see how that
> would work, unless some clot has got a channel in anti-phase.
Obviously it's only the extra noise from the L-R channel that cancels.
The noise on the L+R channel will still be present just as it would if you
switched the tuner/receiver to mono.
Brian Gregory [UK]
"DAB sounds worse than FM" <dab.is@dead> wrote in message
> No, no noise is cancelled.
So you're saying x minus x doesn't equal zero now?
This really is laughable.
Brian Gregory [UK]
> Two different random noise sources are added together. I suppose a tiny
> bit might be randomly cancelled. :-)
FFS.
THEY ARE NOT DIFFERENT.
THERE IS ONLY ONE L-R SIGNAL WITH ONE LOT OF NOISE ON IT.
I CAN'T BELIEVE ANYONE WHO CLAMS TO HAVE ANY TECHNICAL ABILITY CAN FAIL TO
SEE THIS.
Brian Gregory [UK]
> But for the random noise that was in the stereo sub carrier, you are not
> just adding two random sources together, you are adding together two
> opposite copies of the *same* random source.
Exactly.
Peter Watson
> jami...@excite.com wrote:
>> On Apr 26, 9:48 am, "DAB sounds worse than FM" <dab.is@dead> wrote:
>>
<snip>
>
> In the settings of the Morphy Ricahrds 27024 it was set to "stereo", not
> mono. These receiver modules are implemented using software-defined radio,
> so if the radio is set to stereo the software will do the necessary
> processing to form the stereo signal, and the L and R signals will be sent
> to the appropriate pins on the receiver module so that they can be amplified
> and sent to the speaker. For single-speaker DAB portable radios they'll only
> connect to one of the pins, obviously.
>
<snip>
Utter nonsense - You have the circuit diagram to confirm this
arrangement presumably?
I'll leave you to consider why this is a ridiculous suggestion :)
Clues:
Stereo drama with characters panned left & right?
Pre & Power amp arrangements including feeds to possible line out and
headphone sockets?
Peter
jami...@excite.com
> "DAB sounds worse than FM" <dab.is@dead> wrote in messagenews:O9sQj.59579$h65....@newsfe2-gui.ntli.net...
>
> > Here's a way that might convince you that you're wrong: the FFT is a
> > linear operation, so if you took the FFT of two noise signals with
> > different spectra, if they were equal you should be able to subtract the
> > two spectral representations and have a result of zero across the whole
> > spectrum. But as the noise spectra are different, if you subtracted one
> > from teh other you obviously wouldn't get zero, hence the two signals
> > cannot be the same.
>
> I've respected you as knowledgeable but rather argumentative until now (not
> unlike me).
> But I'm afraid this makes you look like a total tech moron.
I'm glad he's finally been exposed as an idiot in such an obvious
way. :-) Some people on here were still taking him seriously.
All the random bullsh*t equations he's posted in this thread, plus the
above nonsense, then his pretending that the radio he was testing only
had one stereo channel connected to the internal mono speaker, all in
a desperate effort to hide that fact that he's shown himself up as not
even understanding how simple, old-fashioned FM MPX stereo works.
Here's a quote from earlier in this thread, from before he realised
he'd been proved wrong, which exposes him for all to see:
****
DAB sounds worse than FM wrote:
> Boltar wrote:
> > Agreed , but if you have a radio that always decodes stereo no matter
> > what mode its in , but for mono mode literally just feeds the 2 stereo
> > channels into one speaker then I think you'll still hear the stereo
> > hiss.
> I haven't suggested otherwise.
****
Richard Evans
Actually, although it seems like a stupid thing to do, I can believe
that perhaps once the bean counters got hold of the design, they might
do something like that, to save a few pennies on the production costs.
Richard E.
Richard Evans
> "Richard Evans" <R.P.Evan...@NTLWorld.com> wrote in message
> news:aiqQj.15901$244....@newsfe1-win.ntli.net...
>> However I'm trying to point out that what works in theory, doesn't always
>> work in practice.
>
> How many times have you done it and found it didn't cancel out?
>
> I've done it with at least five different tuners and they all cancelled out
> closely enough that there was no audible difference from switching the tuner
> to mono.
>
> Something is wrong if they don't cancel at very well.
>
only tried it on 2 or 3 receivers, and never on any of these poor
quality DAB/FM receivers. So I did wonder whether something in one of
these poor receivers might not be lined up so well, which might end up
affecting the cancellations. Basically I don't like to rule anything out
unless I know exactly what is going on.
Richard E.
DAB sounds worse than FM
> "Richard Evans" <R.P.Evan...@NTLWorld.com> wrote in message
> news:a8HQj.44392$B83....@newsfe3-gui.ntli.net...
>> But for the random noise that was in the stereo sub carrier, you are
>> not just adding two random sources together, you are adding together
>> two opposite copies of the *same* random source.
>
> Exactly.
Wrong. Scroll down to the Stereo section on here:
http://www.radio-electronics.com/info/broadcast/vhffm/vhf_fm.php
The mono signal is ready and waiting to be used. Where on earth you get the
idea that you need to add different signals together from I really have no
idea.
DAB sounds worse than FM
> "Malcolm Knight" <firstinitial....@spam-trap.co.uk> wrote in
> message news:67gs7sF...@mid.individual.net...
>> Two different random noise sources are added together. I suppose a
>> tiny bit might be randomly cancelled. :-)
>
> FFS.
>
> THEY ARE NOT DIFFERENT.
>
> THERE IS ONLY ONE L-R SIGNAL WITH ONE LOT OF NOISE ON IT.
The L-R signal ISN'T USED for mono. WTF are you going on about?
> I CAN'T BELIEVE ANYONE WHO CLAMS TO HAVE ANY TECHNICAL ABILITY CAN
> FAIL TO SEE THIS.
Oh, the irony.
DAB sounds worse than FM
I can only imagine that Jamie got the wrong end of the stick, and this has
led to you, Brian Gregory and Peter Watson all being led down some garden
path that you didn't need to go down, because the mono signal is sitting
there ready and waiting to be used without any further processing being
required, so all this talk about noise signals cancelling one another is
just bollocks.
> as you seem to have proved
> what I have been trying to say all along. That is that adding together
> the Left and Right channels from an FM stereo radio achieves the same
> result as having the radio receive in mono in the first place.
Well, yes.
> I think the only reason why we got onto this discussion is that I
> didn't realize that the Morphy Richards radio only outputted one of
> the stereo channels to the speaker (not the sum of both channels).
> Therefore it seemed strange to me that it produced more noise when in
> stereo mode.
It uses software-defined radio, so the software just calculates what it's
supposed to do given the radio's settings.
> If it had fed it's single speaker with the sum of both
> Left and Right channels,
No, that sounds like you still haven't understood what really happens, which
is that you have the mono signal sitting there ready and waiting to be used
so there is absolutely no point in summing the Left and Right channels
together.
Here's a figure of the FM spectrum:
http://www.radio-electronics.com/info/broadcast/vhffm/vhf_fm03.gif
The mono signal is simply lowpass filtered and output to the amplifier.
There's no point in reconstructing the Left and the Right stereo signals and
then adding them together just to get the exact same things (L+R) as you
already have sitting there at baseband.
DAB sounds worse than FM
> "DAB sounds worse than FM" <dab.is@dead> wrote in message
> news:5wGQj.72763$jH5....@newsfe3-win.ntli.net...
>> No, no noise is cancelled.
>
> So you're saying x minus x doesn't equal zero now?
>
> This really is laughable.
What is laughable is people who claim they know what they're talking about
suggesting that a mono portable radio will first form the Left and Right
stereo signals and then add these reconstructed Left and Right channels
together when you've already got the L+R mono signal sitting there ready and
waiting to be used.
DAB sounds worse than FM
> On Apr 26, 4:30 pm, "Malcolm Knight" <firstinitial.secondinit...@spam-
> trap.co.uk> wrote:
>
>> Not missing it, but I'm wondering why your simple solution isn't the
>> one always adopted instead of defeating the stereo decoder which has
>> been the traditional method since the 1950s. I suspect that this is
>> where a little knowledge is a dangerous thing. Not that I am in a
>> position to prove you wrong.
>
> Maybe you should shut up then?
I've just read a few posts from earlier in the thread, including reading
some of yours on Google Groups, and the people to blame for misunderstanding
how FM receivers work, which is what's led to some of the idiotic discussion
on this sub-thread, were you and Boltar talking utter crap.
For example:
http://groups.google.com/group/alt.radio.digital/msg/c1c6ea6348ec5ac1
"> The L+R channel noise are not exactly
> duplicates 180 degrees out of phase so when you add the L+R channels
> back together you just get 2 channels of random noise summed.
They are exact duplicates because they're both derived from the same
AM subcarrier demodulator. I've just tested this with a weak FM signal
on my hi-fi tuner and regardless of whether I switch the amplifier to
mono, or the FM tuner to mono, or both, the result is the same - the
hiss disappears."
The hiss is not eliminated, the SNR goes up.
http://groups.google.com/group/alt.radio.digital/msg/b2331d0bf6f85062
"The simple fact is that hiss from decoded FM stereo is always 180
degrees out of phase and will, therefore, always cancel itself out
when the left and right channels are combined."
The left and right channels are NOT added together in the FM receiver,
because there is already an L+R signal sitting there at baseband ready and
waiting to be used.
You are the one who's been to blame for getting this wrong and leading the
others down the wrong path.
> FM Multiplex stereo decoding is all very simple logic - obviously way
> over Steve's head, but if it's over yours too then I think you should
> stop making a fool of yourself right now.
Yet in reality it was you who didn't understand it all along.
Richard Evans
> Brian Gregory [UK] wrote:
>> "Richard Evans" <R.P.Evan...@NTLWorld.com> wrote in message
>> news:a8HQj.44392$B83....@newsfe3-gui.ntli.net...
>>> But for the random noise that was in the stereo sub carrier, you are
>>> not just adding two random sources together, you are adding together
>>> two opposite copies of the *same* random source.
>> Exactly.
>
>
> Wrong. Scroll down to the Stereo section on here:
>
> http://www.radio-electronics.com/info/broadcast/vhffm/vhf_fm.php
>
> The mono signal is ready and waiting to be used. Where on earth you get the
> idea that you need to add different signals together from I really have no
> idea.
>
>
you have to do it the long way round, by adding the two output channels
together. It was all about the theory of whether or not the noise would
actually cancel, if you did this.
You started this by saying that stereo reception produced more noise
than mono, in a radio that has only one speaker. Now to me, (and
presumably to many other people) it seems sensible that a radio that
does this would add the left and right channels together, and this makes
it hard to see why there would still be more noise when the radio is in
stereo mode.
If you had just said in the first place that only one of the stereo
channels was sent to the speaker, then that would have explained the
behaviour. Instead you went on about trying to prove that adding the
channels together would not cancel the noise.
I really don't know what to make of all this, you seemed to be trying to
prove something that is simply wrong. I thought perhaps you were
misunderstanding what I was trying to say, but then you kept going on
about how adding the channels together would not cancel the noise. As
far as I can tell nobody was claiming that this was the best and most
sensible way to achieve mono reception, I was just trying to point out
that I think you were wrong to say that it wouldn't work.
Richard E.
DAB sounds worse than FM
> On Apr 26, 6:22 pm, "Malcolm Knight" <firstinitial.secondinit...@spam-
> trap.co.uk> wrote:
>
>>
>> Only when you tell us why early tuner designers didn't come up with
>> the idea of mixing the L/R audio derived from the decoder instead of
>> taking the unadulterated mono signal. The multiplexing process must
>> introduce extra noise so it's counter-intuitive for it to be the
>> ideal solution.
>
> The former is more elegant? The latter involves portions of the
> electronics being operated needlessly, which is an issue where tubes
> are used?
> Who knows, and who cares. Facts are facts. The demodulated difference
> signal, noise and all, gets added to L+R generate the left channel,
> and subtracted from L+R to generate the right channel, leaving you
> with the exact same amount of noise added to the left channel as is
> subtracted from the right.
> I don't know how many times I have to repeat this before you'll accept
> it.
But we're talking about mono FM, not stereo.
> <snip your impression of steve>
>
>>> A very similar method is used on vinyl records incidentally, with
>>> the horizontal groove modulation carrying L+R and an additional
>>> vertical groove modulation carrying L-R.
>>
>> Yeah, I worked that out and modified a pickup a little more than
>> fifty years ago. It sum and differenced the vertical L-R signal and
>> the mono separately rather than take the usual mechanical route of
>> reading the 45 degree groove walls.
>
> And yet you don't understand how FM MPX stereo works.
No, it's you that doesn't.
DAB sounds worse than FM
> DAB sounds worse than FM wrote:
>> jami...@excite.com wrote:
>>> On Apr 26, 9:48 am, "DAB sounds worse than FM" <dab.is@dead> wrote:
>>>
> <snip>
>>
>> In the settings of the Morphy Ricahrds 27024 it was set to "stereo",
>> not mono. These receiver modules are implemented using
>> software-defined radio, so if the radio is set to stereo the
>> software will do the necessary processing to form the stereo signal,
>> and the L and R signals will be sent to the appropriate pins on the
>> receiver module so that they can be amplified and sent to the
>> speaker. For single-speaker DAB portable radios they'll only connect
>> to one of the pins, obviously.
> <snip>
>
> Utter nonsense - You have the circuit diagram to confirm this
> arrangement presumably?
The Morphy Richards 27024 has one speaker and it uses a Radioscape
DAB/DRM/FM/AM receiver module that is implemented using software-defined
radio. One of the main reasons for using software-defined radio is that it
eliminates the need to use analogue components, so are you suggesting that
after all the DSP processing has been done to eliminate the use of analogue
components they decide to use unnecessary analogue components to add the
left and right channel signals together?
Richard Evans
>
>> If it had fed it's single speaker with the sum of both
>> Left and Right channels,
>
>
> No, that sounds like you still haven't understood what really happens, which
> is that you have the mono signal sitting there ready and waiting to be used
> so there is absolutely no point in summing the Left and Right channels
> together.
I do understand that the the best way to receive mono is to just low
pass filter the baseband signal. That is not the point.
The point is that if a radio is receiving a signal in stereo (presumably
just in case somebody plugs in a pair of stereo headphones), but it is
then outputting this signal to just one speaker, then the most sensible
way ought to be to add the two channels together, and that ought to
cancel out the noise from the stereo sub carrier.
> Here's a figure of the FM spectrum:
>
> http://www.radio-electronics.com/info/broadcast/vhffm/vhf_fm03.gif
>
> The mono signal is simply lowpass filtered and output to the amplifier.
> There's no point in reconstructing the Left and the Right stereo signals and
> then adding them together just to get the exact same things (L+R) as you
> already have sitting there at baseband.
Yes I understand that.
If the radio is only outputting to one speaker, then the most sensible
way would be to operate in mono mode, behaving like a simple mono
receiver, and simply ignoring (filtering out) all the stuff above 15khz.
The question is not about how things ought to be done, but it is firstly
about what is happening in this particular receiver.
Secondly the point is about what would actually happen if you did things
the long way around, decoding the stereo signal and then adding it
together. I never said that this is always the most sensible way to
produce mono FM, I'm just saying that when this method is used (for
whatever reason) it ought to work.
Richard E.
DAB sounds worse than FM
> "DAB sounds worse than FM" <dab.is@dead> wrote in message
> news:O9sQj.59579$h65....@newsfe2-gui.ntli.net...
>> Here's a way that might convince you that you're wrong: the FFT is a
>> linear operation, so if you took the FFT of two noise signals with
>> different spectra, if they were equal you should be able to subtract
>> the two spectral representations and have a result of zero across
>> the whole spectrum. But as the noise spectra are different, if you
>> subtracted one from teh other you obviously wouldn't get zero, hence
>> the two signals cannot be the same.
>
> I've respected you as knowledgeable but rather argumentative until
> now (not unlike me).
> But I'm afraid this makes you look like a total tech moron.
You claim to be knowledgable, and yet you're disagreeing with something that
is obviously true.
It is definitely true that if you have say random noise that covers
frequencies from DC up to 15 kHz it will be a different signal to random
noise that is centred at 38 kHz and has a 15 kHz bandwidth. The FFT is a
linear operation, so if you subtracted the spectra of the two noise signals
you wouldn't get zero, therefore the noise signals are not the same.
If you disagree with any of that then you obviously haven't understood what
I wrote, which isn't my problem.
jami...@excite.com
> "The simple fact is that hiss from decoded FM stereo is always 180
> degrees out of phase and will, therefore, always cancel itself out
> when the left and right channels are combined."
>
> The left and right channels are NOT added together in the FM receiver,
> because there is already an L+R signal sitting there at baseband ready and
> waiting to be used.
But if they were added together, for example if the receiver only has
a single mono speaker, then the hiss from decoded FM stereo would
cancel itself out, and the result would be the same as if the FM tuner
was set to 'mono'. That's a simple, clean cut fact which I knew and
you didn't, and there is evidence that you didn't from earlier in this
thread:
****
DAB sounds worse than FM wrote:
> Boltar wrote:
> > Agreed , but if you have a radio that always decodes stereo no matter
> > what mode its in , but for mono mode literally just feeds the 2 stereo
> > channels into one speaker then I think you'll still hear the stereo
> > hiss.
> I haven't suggested otherwise.
****
Do you deny typing this?
> You are the one who's been to blame for getting this wrong and leading the
> others down the wrong path.
bollocks.
Richard Evans
> Peter Watson wrote:
>> DAB sounds worse than FM wrote:
>>> jami...@excite.com wrote:
>>>> On Apr 26, 9:48 am, "DAB sounds worse than FM" <dab.is@dead> wrote:
>>>>
>> <snip>
>>> In the settings of the Morphy Ricahrds 27024 it was set to "stereo",
>>> not mono. These receiver modules are implemented using
>>> software-defined radio, so if the radio is set to stereo the
>>> software will do the necessary processing to form the stereo signal,
>>> and the L and R signals will be sent to the appropriate pins on the
>>> receiver module so that they can be amplified and sent to the
>>> speaker. For single-speaker DAB portable radios they'll only connect
>>> to one of the pins, obviously.
>> <snip>
>>
>> Utter nonsense - You have the circuit diagram to confirm this
>> arrangement presumably?
>
>
> The Morphy Richards 27024 has one speaker and it uses a Radioscape
> DAB/DRM/FM/AM receiver module that is implemented using software-defined
> radio. One of the main reasons for using software-defined radio is that it
> eliminates the need to use analogue components, so are you suggesting that
> after all the DSP processing has been done to eliminate the use of analogue
> components they decide to use unnecessary analogue components to add the
> left and right channel signals together?
>
>
drive the speaker, and that this could be very easily modified to add
the two channels together, with the addition of just one resister and
one capacitor. I hesitate however, thinking, perhaps the amplifier is
built into the receiver module, which might prevent them from doing this.
Do you know whether the amplifier is built into the module, or do they
use an additional chip for this?
Richard E.
Richard Evans
>
> It is definitely true that if you have say random noise that covers
> frequencies from DC up to 15 kHz it will be a different signal to random
> noise that is centred at 38 kHz and has a 15 kHz bandwidth.
Obviously this is true, but I haven't seen anybody in this sub thread
say that it it isn't.
What I and a few others have been saying is that the same random noise
centred around 38khz is added to one output channel and subtracted from
the other. Nobody is trying to say that that this is the same as the
random noise that originated below 15 khz. You keep on bringing this up,
and saying that this is what me and others have been saying, but I
haven't actually seen anybody say this.
The point is that the same signal centred around 38khz is used twice,
inverted in one channel. Therefore anything from that 38khz centred
signal will be cancelled if the two output channels are added together,
not just the stereo image, but the noise around 38khz as well.
The noise below 15khz, is a separate issue, and a complete red herring,
to the point that me and other are trying to make.
Richard E.
Peter Watson
> Peter Watson wrote:
>> DAB sounds worse than FM wrote:
>>> jami...@excite.com wrote:
>>>> On Apr 26, 9:48 am, "DAB sounds worse than FM" <dab.is@dead> wrote:
>>>>
>> <snip>
>>> In the settings of the Morphy Ricahrds 27024 it was set to "stereo",
>>> not mono. These receiver modules are implemented using
>>> software-defined radio, so if the radio is set to stereo the
>>> software will do the necessary processing to form the stereo signal,
>>> and the L and R signals will be sent to the appropriate pins on the
>>> receiver module so that they can be amplified and sent to the
>>> speaker. For single-speaker DAB portable radios they'll only connect
>>> to one of the pins, obviously.
>> <snip>
>>
>> Utter nonsense - You have the circuit diagram to confirm this
>> arrangement presumably?
>
>
> The Morphy Richards 27024 has one speaker and it uses a Radioscape
> DAB/DRM/FM/AM receiver module that is implemented using software-defined
> radio. One of the main reasons for using software-defined radio is that it
> eliminates the need to use analogue components, so are you suggesting that
> after all the DSP processing has been done to eliminate the use of analogue
> components they decide to use unnecessary analogue components to add the
> left and right channel signals together?
>
>
radio would take either the L or the R only to the speaker.
As it happens though I am suggesting that you would combine the L and R
to derive mono post module in order to feed the speaker. I'll let you
work out why... (Hint: You snipped the clues from my original post)
Peter Watson
>
>
> I can only imagine that Jamie got the wrong end of the stick, and this has
> led to you, Brian Gregory and *Peter Watson* all being led down some garden
> path that you didn't need to go down, because the mono signal is sitting
> there ready and waiting to be used without any further processing being
> required, so all this talk about noise signals cancelling one another is
> just bollocks.
>
I said nothing of the sort...
DAB sounds worse than FM
What's flawed about outputting the L+R signal to the single speaker??
> As it happens though I am suggesting that you would combine the L and
> R to derive mono post module in order to feed the speaker. I'll let
> you work out why... (Hint: You snipped the clues from my original
> post)
And why would this be beneficial? Surely it would waste power to keep both
DACs running continuously when you only need to use one, and you'd consume
some power when combining the signals as well. Surely it would be better to
output the L+R signal on one channel and then only have the second DAC
running if the headphone socket were inserted.
DAB sounds worse than FM
> On Apr 27, 11:43 am, "DAB sounds worse than FM" <dab.is@dead> wrote:
>
>> "The simple fact is that hiss from decoded FM stereo is always 180
>> degrees out of phase and will, therefore, always cancel itself out
>> when the left and right channels are combined."
>>
>> The left and right channels are NOT added together in the FM
>> receiver, because there is already an L+R signal sitting there at
>> baseband ready and waiting to be used.
>
> But if they were added together, for example if the receiver only has
> a single mono speaker, then the hiss from decoded FM stereo would
> cancel itself out, and the result would be the same as if the FM tuner
> was set to 'mono'.
I'm not disputing that. What I'm disputing is why you would bother doing
this when you've already got the L+R signal at baseband:
http://www.radio-electronics.com/info/broadcast/vhffm/vhf_fm03.gif
Why would a radio with a single speaker first reconstruct the left and right
stereo signals THEN add them back together only to get a signal that's
already there?
> That's a simple, clean cut fact which I knew and
> you didn't,
Look at what was originally said:
http://groups.google.com/group/alt.radio.digital/msg/67fbea9376187484
"Me: > From memory, it defaulted to stereo reception on FM even though it's
only
> got one speaker, so I had to change the settings to make it default to
> mono
> because with stereo it was a bit hissy.
Again Steve demonstrates his total lack of cluefulness. The mono
speaker carries L+R combined, and when the two channels are combined
all the FM stereo hiss disappears and switching the actual tuner to
mono would make no difference."
Explain to me why the hiss disappeared when I changed the FM mode from
stereo to mono. The exact same thing happened on the Roberts RD20 as well,
and it was also a single-speaker radio. You've suggested that all portable
radios with a single speaker combine the left and right channels prior to
the audio going to the amp and speaker, so how did the hiss disappear?
> and there is evidence that you didn't from earlier in this
> thread:
>
> ****
> DAB sounds worse than FM wrote:
>
>> Boltar wrote:
>>> Agreed , but if you have a radio that always decodes stereo no
>>> matter what mode its in , but for mono mode literally just feeds
>>> the 2 stereo channels into one speaker then I think you'll still
>>> hear the stereo hiss.
>> I haven't suggested otherwise.
>
> ****
>
> Do you deny typing this?
No, but I'll admit that it's wrong now - I've never owned an amp with a mono
button, whereas you have. Big deal.
>> You are the one who's been to blame for getting this wrong and
>> leading the others down the wrong path.
>
> bollocks.
Now explain why I heard hiss on the Morphy Richard which disappeared when I
changed the FM mode from stereo to mono, and why the same thing happened on
a Roberts RD20, and both of these radios use Radioscape DAB receiver
modules. Are you suggesting that the left and right channels were combined
on these two radios? And if so, how do you explain the hiss disappearing??