Radio tuner sensitivity and coax signal loss.

[David Paste]

Hello again.

The manual to my radio states:

Frequency range:
87.5–108.0 MHz (100-kHz step)
Sensitivity:
2.5 μV(IHF)
S/N:
26 dB 2.2 μV

Then this webpage:

https://www.aerialsandtv.com/knowledge/fm-and-dab-radio

says:

"Signal levels for FM & DAB, plus splitting FM/DAB
Some sources say that for FM you should be aiming for a signal level
between 60 and 75dBµV at the tuner input but most tuners will work
fine down to 40dBµV (some even lower) and that includes the
additional signal [15dB or so] that stereo decoders require."


Is the dBuV (decibel microvolts, I know that much, but...) here the same as the uV figure given in the tuner specification?

If so, does this mean I will be laughing with a half wave dipole and 30 or so metres of WF100 from it (at the roof) to the tuner (in the cellar)?

Thanks again you lovely bunch.

[Mark Carver]

The sensitivity quoted (2ish microvolts) is the signal level required
across the input of the tuner for "full quieting". In other words a
noise(*) free mono signal
You need significantly more than that for clean stereo decoding. A good
tuner will do that at around 40-50 dBµV  (200-315 µV ).
For the lowest possible noise in stereo, you need at least 60 dBµV (1
millivolt) However, go above 75 dBµV (about 5mV) and you risk
overloading the tuner,
and introducing intermodulation products and distortion.

* By noise in this context I'm talking about only the noise that's
generated internally by the tuner. In practice, and particularly these
days, trying to listen to a signal that's only 2 microvolts, it'll be
interrupted by lots of external electrical interference, and won't be
practical .

[Mark Carver]

On 05/02/2022 16:45, David Paste wrote:

> If so, does this mean I will be laughing with a half wave dipole and 30 or so metres of WF100 from it (at the roof) to the tuner (in the cellar)?
>

I forgot to answer this question.

WF100 etc has an attenuation at 100 MHz for about 6 or 7dB per 100
metres. Therefore 30 metres will have an attenuation of 2 or 3 dB.

That's not very much, but to work out your 'RF link budget' you need to
know the field strength of your wanted signal, the gain of the aerial,
how much of that ends up as a 'voltage' in your coax, and the loss of
the Co-ax. We only know the latter so far. What are you trying to
receive, and how far away is the transmitter from you (this thread could
run and run....)

[David Paste]

On Saturday, 5 February 2022 at 17:03:04 UTC, Mark Carver wrote:

> A good
> tuner will do that at around 40-50 dBµV (200-315 µV ).

What is the relationship between these two values? I am truly ignorant of this stuff.

Thanks Mark.

[David Paste]

On Saturday, 5 February 2022 at 17:14:49 UTC, Mark Carver wrote:

> That's not very much, but to work out your 'RF link budget' you need to
> know the field strength of your wanted signal,

Can I find that out with a multimeter? :D

> the gain of the aerial,

It'll be a half-wave dipole, so whatever that is I suppose.

> how much of that ends up as a 'voltage' in your coax, and the loss of
> the Co-ax. We only know the latter so far. What are you trying to
> receive

Radios 1-4, Classic FM. All from Holme Moss as far as I know

> and how far away is the transmitter from you (this thread could
> run and run....)

50.37 km according to google maps measuring stick!

Cheers!

[Mark Carver]

Decibels are meaningless unless referenced, so the unit dBµV, are an
expression of voltage referenced to 1 microvolt.

For a voltage ratio, the value is 20log(V2/V1). So say something 1000
times a microvolt, (i.e 1 millivolt) that's 20log(1/1000) or 60dBuV

Actually, I cocked up with my 40-50 dBuV example, I'd referenced the
40dB figure at 2uV and not 1uV, so 40 dBuV relates to 100uV, but 50 dBuV
is  indeed 315uV)

[Mark Carver]

On 05/02/2022 17:39, David Paste wrote:
> On Saturday, 5 February 2022 at 17:14:49 UTC, Mark Carver wrote:
>
>> That's not very much, but to work out your 'RF link budget' you need to
>> know the field strength of your wanted signal,
> Can I find that out with a multimeter? :D

No :-)

>
>> the gain of the aerial,
> It'll be a half-wave dipole, so whatever that is I suppose.

Well, that's used as a 0dB reference for specifying yagi gain, if for
sake of argument we say that it translates a 60dBuv/m field into 60 dBuV
of signal (it doesn't, Bill Wright can give us chapter and verse on real
world figures) then if you're only 30 miles from Holme Moss, you're
likely to be on that contour, so after the feeder loss you're going to
end up with 56 or 57 dBuV at the tuner, not quite the magic 60 figure,
but probably good enough.

>
> Radios 1-4, Classic FM. All from Holme Moss as far as I know
>

However, stop. Why are you wanting to use FM for these stations ? The
days of HiFi quality sound on any FM station are long gone.
You'd be better off (in a fixed receiving environment) using the
internet, satellite, or Freeview for these national stations ?

[Java Jive]

On 05/02/2022 18:23, Mark Carver wrote:
>
> However, stop. Why are you wanting to use FM for these stations ? The
> days of HiFi quality sound on any FM station are long gone.
> You'd be better off (in a fixed receiving environment) using the
> internet, satellite, or Freeview for these national stations ?

Yes, much better to use GetIPlayer to download the 320kbps versions of
the BBC's music output.

--

Fake news kills!

I may be contacted via the contact address given on my website:
www.macfh.co.uk

[williamwright]

On 05/02/2022 16:45, David Paste wrote:

> Is the dBuV (decibel microvolts, I know that much, but...) here the same as the uV figure given in the tuner specification?

dBuV is dB related to 1uV. Incidentally 60dBuV is 1000uV or 1mV.
The sensitivity claim you quote is bollocks, but there again they all
seem to quote figures like that.

>
> If so, does this mean I will be laughing with a half wave dipole and 30 or so metres of WF100 from it (at the roof) to the tuner (in the cellar)?

You won't be laughing if you use it to receive a BBC comedy programme on
Radio Four because they aren't funny anymore. But a vertical half wave
(centre fed) is to all intents and purposes the best FM aerial there is,
and the loss on 30m of WF100 is about half a dB, so negligible.

>
> Thanks again you lovely bunch.

How can you tell? Is there a camera on my computer? I do get a lot of
messages saying that people can see me indulging in self abuse, come to
think of it.

Bill

[williamwright]

On 05/02/2022 17:14, Mark Carver wrote:
> On 05/02/2022 16:45, David Paste wrote:
>> If so, does this mean I will be laughing with a half wave dipole and
>> 30 or so metres of WF100 from it (at the roof) to the tuner (in the
>> cellar)?
>>
> I forgot to answer this question.
>
> WF100 etc has an attenuation at 100 MHz for about 6 or 7dB per 100
> metres. Therefore 30 metres will have an attenuation of 2 or 3 dB.

Yes you're right Mark. I thought he wrote 30 feet. I was visualising the
distance it normally is from the roof to the cellar.

Bill

[williamwright]

On 05/02/2022 17:03, Mark Carver wrote:
> The sensitivity quoted (2ish microvolts) is the signal level required
> across the input of the tuner for "full quieting". In other words a
> noise(*) free mono signal

To be honest I've never encountered a tuner that would give anything
like noise free-reception on such a low signal. Not in the real world.
But 6dBuV -- no. 15 to 20dBuV I'd say yes, with a following wind. Maybe
external noise has always been the limiting factor, because when I've
been struggling with this it's usually been somewhere noisy, and with
other signals at around 60dBuV.

> You need significantly more than that for clean stereo decoding. A good
> tuner will do that at around 40-50 dBµV  (200-315 µV ).

Agreed.

> For the lowest possible noise in stereo, you need at least 60 dBµV (1
> millivolt) However, go above 75 dBµV (about 5mV) and you risk
> overloading the tuner,
> and introducing intermodulation products and distortion.

It always used to be a problem when the hi-fi buffs insisted on a six
element aerial when you could see nearby Holme Moss from the roof.
Still, it sold "these special things that reduce the strength without
spoiling the quality" at a fiver each. It was great when the 50p gold
coloured ones came out...

>
> * By noise in this context I'm talking about only the noise that's
> generated internally by the tuner. In practice, and particularly these
> days, trying to listen to a signal that's only 2 microvolts, it'll be
> interrupted by lots of external electrical interference, and won't be
> practical .

Yes.

I've often said the same thing about UHF TV reception when the city is
compared to the country.

Bill

[Java Jive]

On 05/02/2022 18:37, williamwright wrote:
>
> You won't be laughing if you use it to receive a BBC comedy programme on
> Radio Four because they aren't funny anymore. But a vertical half wave
> (centre fed) is to all intents and purposes the best FM aerial there is,
> and the loss on 30m of WF100 is about half a dB, so negligible.

I've just been listening to The News Quiz, and laughed a lot more than I
do at your needle-stuck-in-the-groove grumblings.

[charles]

In article <j680v6...@mid.individual.net>,

2mV would be a sensible level for stereo. Could there be a typo somewhere?

--
from KT24 in Surrey, England
"I'd rather die of exhaustion than die of boredom" Thomas Carlyle

[Jim Lesurf]

In article <j67ou5...@mid.individual.net>, Mark Carver

<mark....@invalid.invalid> wrote:
> The sensitivity quoted (2ish microvolts) is the signal level required
> across the input of the tuner for "full quieting".

Quibble. Some times it is for 30dB SNR for a standard signal level, or for
60dB. i.e. not always the saturation quieting. And may be for mono,
glossing over actual stereo. (Which will be poorer even on a mono set
because stereo means a lower L+R level.)

Jim

--
Please use the address on the audiomisc page if you wish to email me.
Electronics https://www.st-andrews.ac.uk/~www_pa/Scots_Guide/intro/electron.htm
biog http://jcgl.orpheusweb.co.uk/history/ups_and_downs.html
Audio Misc http://www.audiomisc.co.uk/index.html

[Jim Lesurf]

In article <j67tki...@mid.individual.net>, Mark Carver

<mark....@invalid.invalid> wrote:
> However, stop. Why are you wanting to use FM for these stations ? The
> days of HiFi quality sound on any FM station are long gone. You'd be
> better off (in a fixed receiving environment) using the internet,
> satellite, or Freeview for these national stations ?

Slight cavil on that. Although for serious 'sit and listen' I tend to
prefer R3 via iplayer 320k, I find that R3/FM on a decent tuner sound very
good. The way the level compression, etc, is applied actually make it sound
warmer and easier to hear.

[Mark Carver]

On 05/02/2022 19:20, williamwright wrote:
> On 05/02/2022 17:03, Mark Carver wrote:
>> The sensitivity quoted (2ish microvolts) is the signal level required
>> across the input of the tuner for "full quieting". In other words a
>> noise(*) free mono signal
>
> To be honest I've never encountered a tuner that would give anything
> like noise free-reception on such a low signal. Not in the real world.
> But 6dBuV -- no. 15 to 20dBuV I'd say yes, with a following wind.
> Maybe external noise has always been the limiting factor, because when
> I've been struggling with this it's usually been somewhere noisy, and
> with other signals at around 60dBuV.
>
>> You need significantly more than that for clean stereo decoding. A

>> good tuner will do that at around 40-50 dBµV  (100-315 µV ).
>
> Agreed.

When I was a lad, I used to receive Capital, LBC, and BBC R London at
about 40 dBµV, (45 miles west of London using a three element yagi,
looking at Croydon/CP)

Perfectly good stereo reception for all three. The only problem was a
pesky high power Belgian station 100kHz below Capital, that used to pop
up at the merest hint of a lift, and spoil things by introducing the
birdies. Switching to mono cleaned those away.

[williamwright]

On 06/02/2022 13:34, Mark Carver wrote:
> When I was a lad, I used to receive Capital, LBC, and BBC R London at
> about 40 dBµV, (45 miles west of London using a three element yagi,
> looking at Croydon/CP)

Ha! That's nowt! When I were a lad I used to receive Capital, LBC, and
BBC R London on a one element yagi!

Ha! You should be so lucky! When I were a lad I used to receive Capital,
LBC, and BBC R London on a bit of wet string!

We used to live in a tiny tumble down house with no electricity so the
only way to receive Capital, LBC, and BBC R London was with a crystal
set. We were poor but we were happy!

We were happy because we were poor! We couldn't afford a crystal set so

(cont p92)

[Brian Gaff (Sofa)]

I had to sort through the coal in every sack till I found one which
functioned as a crystal, it was the cats whiskers of course.
OK enough silliness.
Does anyone recall those early cassette stereo portables with the image
width control. The idea I think was that as you progressed from wide, ie
anti phase to mono, completely in phase and joined the his could be reduced
the nearer you got to mono.

Another Philips gimmick. I remember some of their stereo systems of the 70s
had very good turntables and some kind of illumination of the dial that
subtly changed colour with signal strength, then there was the Tandy Tuners
which turned of the AFC while you gripped the tuning knob and turned it on
when you let go.
Brian

--

This newsgroup posting comes to you directly from...
The Sofa of Brian Gaff...
bri...@blueyonder.co.uk
Blind user, so no pictures please
Note this Signature is meaningless.!
"williamwright" <wrights...@f2s.com> wrote in message
news:j6aro2...@mid.individual.net...

[David Paste]

On Saturday, 5 February 2022 at 18:15:06 UTC, Mark Carver wrote:

> Decibels are meaningless unless referenced, so the unit dBµV, are an
> expression of voltage referenced to 1 microvolt.
>
> For a voltage ratio, the value is 20log(V2/V1). So say something 1000
> times a microvolt, (i.e 1 millivolt) that's 20log(1/1000) or 60dBuV
>
> Actually, I cocked up with my 40-50 dBuV example, I'd referenced the
> 40dB figure at 2uV and not 1uV, so 40 dBuV relates to 100uV, but 50 dBuV
> is indeed 315uV)

*nods along blankly* ;) Thanks for the effort though!

[David Paste]

On Saturday, 5 February 2022 at 18:23:16 UTC, Mark Carver wrote:

> However, stop. Why are you wanting to use FM for these stations ? The
> days of HiFi quality sound on any FM station are long gone.
> You'd be better off (in a fixed receiving environment) using the
> internet, satellite, or Freeview for these national stations ?

I know, I can get them via the internet in the cellar, but I like the
radio. I like using the radio, everything about it. Don't ask me
why. I like CDs too.

[David Paste]

On Saturday, 5 February 2022 at 18:32:12 UTC, Java Jive wrote:

> Yes, much better to use GetIPlayer to download the 320kbps versions of
> the BBC's music output.

Cheers, yeah I do if I want to keep something.

[David Paste]

On Saturday, 5 February 2022 at 18:37:29 UTC, wrights...@aol.com wrote:

> But a vertical half wave
> (centre fed) is to all intents and purposes the best FM aerial there is,

Is this the same as a half-wave dipole? same thing / different name?

> > Thanks again you lovely bunch.
> How can you tell? Is there a camera on my computer? I do get a lot of
> messages saying that people can see me indulging in self abuse, come to
> think of it.

I've been advised not to answer.

[David Paste]

On Sunday, 6 February 2022 at 10:56:00 UTC, Jim Lesurf wrote:

> Slight cavil on that. Although for serious 'sit and listen' I tend to
> prefer R3 via iplayer 320k, I find that R3/FM on a decent tuner sound very
> good. The way the level compression, etc, is applied actually make it sound
> warmer and easier to hear.
> Jim

Wot 'e sed.

Things may or may not be lacking in FM broadcast signals quantitavely, but
qualitative listening experience = Radio 3 on FM sounds gorgeous to my ears.

[David Paste]

On Sunday, 6 February 2022 at 13:34:32 UTC, Mark Carver wrote:

> When I was a lad, I used to receive Capital, LBC, and BBC R London at
> about 40 dBµV, (45 miles west of London using a three element yagi,
> looking at Croydon/CP)

How do you measure this? Do you need a special meter?

[charles]

In article <03a74269-b0cc-46a4...@googlegroups.com>,

yes, you need a signal strength meter.

[williamwright]

On 07/02/2022 19:30, David Paste wrote:
> On Saturday, 5 February 2022 at 18:37:29 UTC, wrights...@aol.com wrote:
>
>> But a vertical half wave
>> (centre fed) is to all intents and purposes the best FM aerial there is,
>
> Is this the same as a half-wave dipole? same thing / different name?

Yes. In practice it's going to be centre fed.

Bill

[williamwright]

Yes.

Bill

[Brian Gaff (Sofa)]

One has to also beware of published specs. I bought a Rotel tuner which got
good reviews on its performance both in sensitivity, and its strong signal
handling, but although it was fine for both of these and also s/N, it
sounded leaden, no matter what you did when put against a Pioneer or
Armstrong at the time.
I eventually sold it on, and bought a Pioneer which lasted for many years
till it started to have semiconductor failures in the small signal parts and
the over complex string dial and lights failed.

It turned out the problem was the very aggressive filtering of the bandwidth
giving phase distortions, a bit like an audio noth filter can ring.

Brian

--

This newsgroup posting comes to you directly from...
The Sofa of Brian Gaff...
bri...@blueyonder.co.uk
Blind user, so no pictures please
Note this Signature is meaningless.!
"williamwright" <wrights...@f2s.com> wrote in message

news:j6e1ca...@mid.individual.net...

> On 07/02/2022 19:36, David Paste wrote:
>> On Sunday, 6 February 2022 at 13:34:32 UTC, Mark Carver wrote:
>>
>>> When I was a lad, I used to receive Capital, LBC, and BBC R London at

>>> about 40 dBÁV, (45 miles west of London using a three element yagi,

[Jim Lesurf]

In article <j6aro2...@mid.individual.net>, williamwright

<wrights...@f2s.com> wrote:

> We used to live in a tiny tumble down house with no electricity so the
> only way to receive Capital, LBC, and BBC R London was with a crystal
> set. We were poor but we were happy!

You must be much younger than me. When I lived in London and used a crystal
set (made by an uncle for me) there were no such stations on any band. So
even with a wire from the house down to the end of the garden I wouldn't
have been able to hear them if they'd been TXing AM on the MW/LW band.

Later on, I do recall hearing Radio Caroline, etc, on my tranny in the
garden, though. I still have that radio but it doesn't work any more. Never
got around to trying to fix it. Not exactly 'hi fi'.

[Jim Lesurf]

In article <stqis5$c4j$1...@dont-email.me>, Brian Gaff \(Sofa\)

<bri...@blueyonder.co.uk> wrote:
> then there was the Tandy Tuners which turned of the AFC while you
> gripped the tuning knob and turned it on when you let go.

The Yamaha CT7000 also does that. Superb FM tuner.

[Jim Lesurf]

In article <stt97d$of4$1...@dont-email.me>, Brian Gaff \(Sofa\)

<bri...@blueyonder.co.uk> wrote:
> One has to also beware of published specs. I bought a Rotel tuner which
> got good reviews on its performance both in sensitivity, and its strong
> signal handling, but although it was fine for both of these and also
> s/N, it sounded leaden, no matter what you did when put against a
> Pioneer or Armstrong at the time. I eventually sold it on, and bought a
> Pioneer which lasted for many years till it started to have
> semiconductor failures in the small signal parts and the over complex
> string dial and lights failed.

> It turned out the problem was the very aggressive filtering of the
> bandwidth giving phase distortions, a bit like an audio noth filter can
> ring.

Yes. That's a point tuner reviews generally overlooked. It can also
increase intermod distortion for stereo FM.

I suspect most reviewers (except ones like Fred Judd and Angus McK) had no
clue that a tight IF improved other specs at the expense of the sound
quality. When adjacent channel selectivity became a selling point for a
while that was a pest. Fortunately, good tuners either kept a sensible
width, or allowed it to be switched.

Case of chasing one spec to 'sell' regardless of the effect on actual in
use performance. Also showed that some reviewers were clueless.

[Mark Carver]

On 07/02/2022 19:36, David Paste wrote:

Yep, borrowed from the MoD, but that's quite another story !

Wrotham R2/3/4; 20 miles further away, in more or less the same
direction (for something as blunt as a 3 element yagi) but at 240kW
(rather than 2 kW) so
10Log(240/2) = 20dB higher power, was about  48 dBuV I think.

[R. Mark Clayton]

I was lucky and spotted a small piece of galena walking in the Ochils when about 11 or 12. It worked as a crystal in a crystal set, although the results were better with a diode.

[David Paste]

On Tuesday, 8 February 2022 at 16:49:33 UTC, Mark Carver wrote:

> Yep, borrowed from the MoD, but that's quite another story !

How do they work?

[Brian Gregory]

It's called a logarithmic scale.

0dBuV = 1uV
20dBuV = 10uV
40dBuV = 100uV
60dBuV = 1000uV
80dBuV = 10000uV

--
Brian Gregory (in England).

[Mark Carver]

How long have you got ?

The most basic model is simply a normal receiver, but with a moving coil
meter fed off of the AGC control line (Automatic Gain Control)
In fact lots of FM tuners back in the day had a little moving coil meter
for signal strength indication. The key to it is for it to have
meaningful calibration, which I don't recall any tuner had ?

Present day TVs and DAB radios have bar-graphs for signal strength, same
principle, except they have nonsense calibration, such as using
percentages (of what ?)

Don't get confused with the Signal _Quality_ meters they also have,
those are a measure in some way of error correction that's being applied.

For digital reception alignment and set up, you really need a proper
spectrum analyser, as it's not just about raw signal strength.

Internet rabbit hole:-

https://www.promaxelectronics.com/ing/

[R. Mark Clayton]

On Saturday, 5 February 2022 at 16:45:39 UTC, David Paste wrote:
> Hello again.
>
> The manual to my radio states:
>
> Frequency range:
> 87.5–108.0 MHz (100-kHz step)
> Sensitivity:
> 2.5 μV(IHF)
> S/N:
> 26 dB 2.2 μV
>
> Then this webpage:
>
> https://www.aerialsandtv.com/knowledge/fm-and-dab-radio
>
> says:
>
> "Signal levels for FM & DAB, plus splitting FM/DAB
> Some sources say that for FM you should be aiming for a signal level
> between 60 and 75dBµV at the tuner input but most tuners will work
> fine down to 40dBµV (some even lower) and that includes the
> additional signal [15dB or so] that stereo decoders require."
>
>
> Is the dBuV (decibel microvolts, I know that much, but...) here the same as the uV figure given in the tuner specification?
>
> If so, does this mean I will be laughing with a half wave dipole and 30 or so metres of WF100 from it (at the roof) to the tuner (in the cellar)?

>
> Thanks again you lovely bunch.

Answering the questions - Bill did experiments ages ago that showed that a vertical half wave dipole gave excellent results on FM, a nd good results on DAB (because the length was a multiple of the wavelength. I acted on this and fitted one to replace the circular folded dipole that was very much the modern fashion. There was a huge improvement on FM, with so many stations (Lancaster to Stoke and Sheffield to Liverpool and Wales that there are more than will fit in my Sony receiver's memory (30).

OTOH it is ~12m up in south Manchester.

I don't use it for DAB, because all our receivers pick up plenty of channels without external aerial.

As regards cables the loss per 100m is usually given on sellers' web sites. For FM (~100MHz) these will be about 20dB for 30m. For less loss use better [i.e. more expensive] cable.

[Phil_M]

I once designed and built a receiver to measure field strength. It
covered Bands 1, 2, part of 3, 4 and 5, using a Mullard tuner and
controlled by a single card BBC Micro.

Phil M

[tony sayer]

In article <59b6f9b...@audiomisc.co.uk>, Jim Lesurf
<no...@audiomisc.co.uk> scribeth thus

>In article <stqis5$c4j$1...@dont-email.me>, Brian Gaff \(Sofa\)
><bri...@blueyonder.co.uk> wrote:
>> then there was the Tandy Tuners which turned of the AFC while you
>> gripped the tuning knob and turned it on when you let go.
>
>The Yamaha CT7000 also does that. Superb FM tuner.
>
>Jim
>

You would say that wouldn't you;!....

https://www.fmtunerinfo.com/yamaha.html
--
Tony Sayer


Man is least himself when he talks in his own person.

Give him a keyboard, and he will reveal himself.

[tony sayer]

In article <j67tki...@mid.individual.net>, Mark Carver

<mark....@invalid.invalid> scribeth thus
>On 05/02/2022 17:39, David Paste wrote:
>> On Saturday, 5 February 2022 at 17:14:49 UTC, Mark Carver wrote:
>>
>>> That's not very much, but to work out your 'RF link budget' you need to
>>> know the field strength of your wanted signal,
>> Can I find that out with a multimeter? :D
>No :-)
>>
>>> the gain of the aerial,
>> It'll be a half-wave dipole, so whatever that is I suppose.
>
>Well, that's used as a 0dB reference for specifying yagi gain, if for
>sake of argument we say that it translates a 60dBuv/m field into 60 dBuV
>of signal (it doesn't, Bill Wright can give us chapter and verse on real
>world figures) then if you're only 30 miles from Holme Moss, you're
>likely to be on that contour, so after the feeder loss you're going to
>end up with 56 or 57 dBuV at the tuner, not quite the magic 60 figure,
>but probably good enough.
>>
>> Radios 1-4, Classic FM. All from Holme Moss as far as I know

>>
>However, stop. Why are you wanting to use FM for these stations ? The
>days of HiFi quality sound on any FM station are long gone.

Dunno R3 is very good from time to time..

>You'd be better off (in a fixed receiving environment) using the
>internet, satellite, or Freeview for these national stations ?

Yes but almost all will have audio processing apart from maybe some net
streams during such times as the Proms..

[tony sayer]

In article <j6fl8q...@mid.individual.net>, Mark Carver
<mark....@invalid.invalid> scribeth thus

>On 07/02/2022 19:36, David Paste wrote:
>> On Sunday, 6 February 2022 at 13:34:32 UTC, Mark Carver wrote:
>>
>>> When I was a lad, I used to receive Capital, LBC, and BBC R London at

>>> about 40 dB0 >>> looking at Croydon/CP)

>> How do you measure this? Do you need a special meter?
>Yep, borrowed from the MoD, but that's quite another story !
>
>Wrotham R2/3/4; 20 miles further away, in more or less the same
>direction (for something as blunt as a 3 element yagi) but at 240kW
>(rather than 2 kW) so
>10Log(240/2) = 20dB higher power, was about  48 dBuV I think.

Wouldn't argue with my Hon friend but that 240 kW is the sum of Vertical
and horizontal components ..

Mind you the TX aerial is rarely perfectly Ommni....

http://txfeatures.mb21.co.uk/wrotham/mixedpol.php

[Mark Carver]

On 12/02/2022 13:24, tony sayer wrote:
> In article <j6fl8q...@mid.individual.net>, Mark Carver
> <mark....@invalid.invalid> scribeth thus
>> On 07/02/2022 19:36, David Paste wrote:
>>> On Sunday, 6 February 2022 at 13:34:32 UTC, Mark Carver wrote:
>>>
>>>> When I was a lad, I used to receive Capital, LBC, and BBC R London at
>>>> about 40 dB0 >>> looking at Croydon/CP)
>>> How do you measure this? Do you need a special meter?
>> Yep, borrowed from the MoD, but that's quite another story !
>>
>> Wrotham R2/3/4; 20 miles further away, in more or less the same
>> direction (for something as blunt as a 3 element yagi) but at 240kW
>> (rather than 2 kW) so
>> 10Log(240/2) = 20dB higher power, was about  48 dBuV I think.
> Wouldn't argue with my Hon friend but that 240 kW is the sum of Vertical
> and horizontal components ..
>
>

Well yes, but so was Croydon's 2kW (1+1kW) so the difference in power
was still 20dB, however you look at it ?

[Rink]

Op 5-2-2022 om 19:15 schreef Mark Carver:
> On 05/02/2022 17:36, David Paste wrote:
>> On Saturday, 5 February 2022 at 17:03:04 UTC, Mark Carver wrote:
>>
>>> A good
>>> tuner will do that at around 40-50 dBµV  (200-315 µV ).
>> What is the relationship between these two values? I am truly ignorant
>> of this stuff.

>>
>>
> Decibels are meaningless unless referenced, so the unit dBµV, are an
> expression of voltage referenced to 1 microvolt.
>
> For a voltage ratio, the value is 20log(V2/V1). So say something 1000
> times a microvolt, (i.e 1 millivolt) that's 20log(1/1000) or 60dBuV

20log(1000/1) I think?

[Mark Carver]

On 05/03/2022 17:22, Rink wrote:
> Op 5-2-2022 om 19:15 schreef Mark Carver:
>> On 05/02/2022 17:36, David Paste wrote:
>>> On Saturday, 5 February 2022 at 17:03:04 UTC, Mark Carver wrote:
>>>
>>>> A good
>>>> tuner will do that at around 40-50 dBµV  (200-315 µV ).
>>> What is the relationship between these two values? I am truly
>>> ignorant of this stuff.
>>>
>>>
>> Decibels are meaningless unless referenced, so the unit dBµV, are an
>> expression of voltage referenced to 1 microvolt.
>>
>> For a voltage ratio, the value is 20log(V2/V1). So say something 1000
>> times a microvolt, (i.e 1 millivolt) that's 20log(1/1000) or 60dBuV
>
> 20log(1000/1)   I think?

Yes, I was upside down !

[Jim Lesurf]

In article <j8hklg...@mid.individual.net>, Mark Carver

I found that the easiest way to teach people (ok, undergrads, not actually
people 8-] ) this was to emphasise that by definition dB was a log *power*
ratio. Hence the extra factor of 2 when using a voltage ratio t get a
result in dB.