Required SNR on FM for stereo and mono?
DAB sounds worse than FM
Alternatively, if you don't know the exact minimum required SNR levels on FM
for mono and stereo, if you know the difference between the two levels that
would still be useful.
--
Steve - www.digitalradiotech.co.uk - Digital Radio News & Info
Find the cheapest Freeview & DAB prices:
http://www.digitalradiotech.co.uk/freeview/freeview_receivers.php
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harrogate3
"DAB sounds worse than FM" <dab.is@dead> wrote in message
news:NYGFh.32419$s47....@newsfe4-gui.ntli.net...
I would doubt that there is a SNR that defines stereo or mono, or do
you mean what SNRs would be expected in stereo or in mono?
Either way it will vary with the tuner sensitivity.
--
Woody
harrogate3 at ntlworld dot com
DAB sounds worse than FM
I'm just after ballpark figures for what the "minimum" required SNR is on FM
for mono and for stereo. I realise it will vary from model to model.
For example, if there's an SNR level that produces faint hiss on stereo,
then there should also be an SNR level that produces a faint hiss on mono,
and what I'm most interested in is what the difference is between these two
levels of SNR (approximately) - i.e. what "gain" does pressing the mono
button on FM provide?
So I'm most interested in the difference in SNR levels between mono and
stereo, but if anybody knows the actual ballpark figures then that would be
a bonus.
Malcolm Knight
"DAB sounds worse than FM" <dab.is@dead> wrote in message
> For example, if there's an SNR level that produces faint hiss on
> stereo, then there should also be an SNR level that produces a faint
> hiss on mono, and what I'm most interested in is what the difference
> is between these two levels of SNR (approximately) - i.e. what "gain"
> does pressing the mono button on FM provide?
>
> So I'm most interested in the difference in SNR levels between mono
> and stereo, but if anybody knows the actual ballpark figures then that
> would be a bonus.
I have a vague recollection from when the Zenith-GE system for FM stereo
was first introduced that the theoretical difference was said to be
23.5dB. Maybe your friend from Surrey will shake up his grey cells too,
or if you are lucky won't have thrown out some of the old documentation.
--
Malcolm
Bill Wright
"harrogate3" <harro...@ntlworld.com> wrote in message
news:L5HFh.1383$Yv5...@newsfe3-win.ntli.net...
> I would doubt that there is a SNR that defines stereo or mono, or do
> you mean what SNRs would be expected in stereo or in mono?
>
> Either way it will vary with the tuner sensitivity.
I can't really see why. The necessary signal level at the tuner input for a
given performance standard will vary with receiver sensitivity, but the
signal to noise ratio will be quotable for a given performance standard.
After all you could feed a tuner with a signal where the s/n ratio was good,
bad, or indifferent. Assuming the signal level was in all cases sufficient
for receiver noise not to be a major factor the s/n ratio at the input would
determine the performance standard, not the tuner sensitivity.
Bill
Bill Wright
"DAB sounds worse than FM" <dab.is@dead> wrote in message
> harrogate3 wrote:
> I'm just after ballpark figures for what the "minimum" required SNR is on
> FM for mono and for stereo. I realise it will vary from model to model.
In the early days of FM stereo the tuners seemed to need a terrifically
strong signal for stereo compared with mono. Of course the tuners in those
didn't have all the present day gimmicks for reducing or hiding hiss. The
difference was at least 12dB as I recall.
Steve, if you have an FM tuner handy I could let you have a selection of
attenuators and you could perform an experiment.
Bill
DAB sounds worse than FM
> "DAB sounds worse than FM" <dab.is@dead> wrote in message
> news:vsHFh.32430$s47....@newsfe4-gui.ntli.net...
>
>> For example, if there's an SNR level that produces faint hiss on
>> stereo, then there should also be an SNR level that produces a faint
>> hiss on mono, and what I'm most interested in is what the difference
>> is between these two levels of SNR (approximately) - i.e. what "gain"
>> does pressing the mono button on FM provide?
>>
>> So I'm most interested in the difference in SNR levels between mono
>> and stereo, but if anybody knows the actual ballpark figures then
>> that would be a bonus.
>
> I have a vague recollection from when the Zenith-GE system for FM
> stereo was first introduced that the theoretical difference was said
> to be 23.5dB.
Thanks - and that tallies with the measurement figures for a few tuners in
Hi-Fi World. For example, one has the following figures:
Stereo separation = 39 dB
Distortion = 0.07%
Hiss (IEC A) = -70 dB
Signal for minimum hiss = 0.5 mV
Sensitivity
mono = 2 uV
stereo = 28 uV
(Looks like I should've dug this info out in the thread about FM's maximum
SNR... hiss = -70 dB...)
Power = V^2 / R
and R is constant because it's the same tuner so the difference in SNR
between mono and stereo should be:
20 log (28 / 2) = 22.9 dB
which is close to 23.5 dB, and the 23.5 dB will only be a guideline anyway.
It does vary from tuner to tuner according to the figures for other tuners,
but most had a difference of over 20 dB.
I'm a bit rusty with the following, but signal power for mono:
P = V^2 / Rantenna = (2 x 10^-6)^2 / 75 = 53. x 10^-15 W
and noise power
N = kTB = 1.38 x 10^-23 x 290 x 200 x 10^3 = 8.004 x 10^-16 W
so
SNRmin_mono = 10 log (53 x 10^-15 / 8 x 10^-16) = 18.2 dB
for stereo, the SNR is the SNR for mono plus the difference in SNR between
stereo and mono, so SNR for stereo is:
SNR_min_stereo = 18.2 + 22.9 = 41.1 dB (this is really C/N)
That sounds about right.
Interestingly, that minimum SNR for stereo is higher than the 40 dB SNR that
Croiset said is the maximum possible SNR for FM!
DAB sounds worse than FM
> "harrogate3" <harro...@ntlworld.com> wrote in message
> news:L5HFh.1383$Yv5...@newsfe3-win.ntli.net...
>> I would doubt that there is a SNR that defines stereo or mono, or do
>> you mean what SNRs would be expected in stereo or in mono?
>>
>> Either way it will vary with the tuner sensitivity.
>
> I can't really see why. The necessary signal level at the tuner input
> for a given performance standard will vary with receiver sensitivity,
> but the signal to noise ratio will be quotable for a given
> performance standard.
Yes, the standard should quote a certain required SNR level.
> After all you could feed a tuner with a signal
> where the s/n ratio was good, bad, or indifferent. Assuming the
> signal level was in all cases sufficient for receiver noise not to be
> a major factor the s/n ratio at the input would determine the
> performance standard, not the tuner sensitivity.
I think the likes of the BBC will take into account how actual receivers
perform though when they're calculating how much power to transmit - that's
if they even bother doing any work on FM any more, as seems to be the way
with the BBC these days...
DAB sounds worse than FM
> "DAB sounds worse than FM" <dab.is@dead> wrote in message
> news:vsHFh.32430$s47....@newsfe4-gui.ntli.net...
>> harrogate3 wrote:
>> I'm just after ballpark figures for what the "minimum" required SNR
>> is on FM for mono and for stereo. I realise it will vary from model
>> to model.
>
> In the early days of FM stereo the tuners seemed to need a
> terrifically strong signal for stereo compared with mono.
Right.
> Of course
> the tuners in those didn't have all the present day gimmicks for
> reducing or hiding hiss. The difference was at least 12dB as I recall.
>
> Steve, if you have an FM tuner handy I could let you have a selection
> of attenuators and you could perform an experiment.
Are they ones I could buy from the likes of Maplins? If so, I think it would
be a good idea if I bought some so that I could use them with future tuners
when testing them.
Richard Evans
> Does anybody know what SNR levels are needed on FM for mono and stereo?
>
> Alternatively, if you don't know the exact minimum required SNR levels on FM
> for mono and stereo, if you know the difference between the two levels that
> would still be useful.
>
>
<Wink Wink>
DAB sounds worse than FM
Yep, maximum of 40 dB - Croiset said so, so it must be true.
hwh
> "DAB sounds worse than FM" <dab.is@dead> wrote in message
> news:vsHFh.32430$s47....@newsfe4-gui.ntli.net...
>> harrogate3 wrote:
>> I'm just after ballpark figures for what the "minimum" required SNR is on
>> FM for mono and for stereo. I realise it will vary from model to model.
>
> In the early days of FM stereo the tuners seemed to need a terrifically
> strong signal for stereo compared with mono. Of course the tuners in those
> didn't have all the present day gimmicks for reducing or hiding hiss. The
> difference was at least 12dB as I recall.
That must be about right. 4 kW of power was enough for a mono station to
have the same range as a 50 kW stereo station, using the same aerial.
gr, hwh
Bill Wright
"DAB sounds worse than FM" <dab.is@dead> wrote in message
> Are they ones I could buy from the likes of Maplins? If so, I think it
> would be a good idea if I bought some so that I could use them with future
> tuners when testing them.
Oh Steve, I've just had a look and they sell 60p ones for a fiver each. They
probably won't be accurate or consistent across different frequencies.
CPC have a variety of decent ones (some variable) for about £3 each. I
happen to know that the current Antiference ones are fairly accurate because
I sorted something out for someone recently who had a meter that wouldn't
read strong signals properly, and we tested a few.
If you don't use CPC you could try the local TV shop. Failing that, email me
your postal address and and I'll shove some in a jiffy bag for you.
Guess what, I've been quite near to your pad today (well, New Mills), so I
could have thrown some through your window!
Bill
Mark Carver
> Does anybody know what SNR levels are needed on FM for mono and stereo?
It's whatever the listener would find acceptable for listening, so wouldn't it
be the same for stereo and mono ? Personally for me about 60dB for music.
> Alternatively, if you don't know the exact minimum required SNR levels on FM
> for mono and stereo, if you know the difference between the two levels that
> would still be useful.
A figure of 18dB sticks in my mind as the difference in audio SNR for
reception of the same signal strength using the Zenith system, but as others
have said tricks like 'hi-blend' help erode this.
Most FM tuners require 60dBuV (1mV) applied to their aerial input for 'full
quieting' on mono (typically about 75ish dB). As Bill says stereo requires
around another 12 dB to deliver the same SNR for stereo ( 72dBuV or 4mV) ?
--
Mark
Please replace invalid and invalid with gmx and net to reply.
Bill Wright
"Mark Carver" <mark....@invalid.invalid> wrote in message
news:54t4fiF...@mid.individual.net...
> Most FM tuners require 60dBuV (1mV) applied to their aerial input for
> 'full quieting' on mono (typically about 75ish dB). As Bill says stereo
> requires around another 12 dB to deliver the same SNR for stereo ( 72dBuV
> or 4mV) ?
I've always worked to the 0dBmV figure given above, but actually I find that
modern FM tuners seem to be able to work tolerably well on much lower signal
levels.
I've carefully looked through all the BBC Eng Info stuff I have about FM
stereo and RDS (1980 to the present) and I can find no mention either of
absolute signal levels or of the differential about which we speak.
Bill
DAB sounds worse than FM
Someone called Mark sent me a copy of a paper about FM from the 1960s
yesterday:
http://www.digitalradiotech.co.uk/FM_Stereophonic_Broadcasting_and_Reception.pdf
(10 MB)
which you and Mark might find interesting.
DAB sounds worse than FM
I've just found this page:
http://www.fmtunerinfo.com/specs.html
and it lists the following two specs as part of a table for a lot of the
tuners listed:
Mono50 1 dBf Mono Sensitivity 50dB Quieting
Ster50 1 dBf Stereo Sensitivity 50dB Quieting
and I've looked at the tuner specs for those listed in the top half of the
page and the difference is always between 18 - 22 dB between stereo and mono
for 50 dB quieting.
Mark Carver
> Someone called Mark sent me a copy of a paper about FM from the 1960s
> yesterday:
>
> http://www.digitalradiotech.co.uk/FM_Stereophonic_Broadcasting_and_Reception.pdf
>
> (10 MB)
>
> which you and Mark might find interesting.
I do; thanks Steve.