Date   

Re: SNR meter, bandwidth and gain adjustment for transverters

jdow
 

I fail utterly to understand that statement. It is coherency effects that can take a 20 MHz wide GPS P/Y-Code signal and coherently reduce it to its baseband 50 Hz bandwidth and decode the ephemeris against a jammer or other noise source that is on the order of 50 dB larger. It is coherency that allows a 200 kHz FM signal to show more than a 10 dB improvement in a 10 kHz bandwidth. The signal components add coherently - as voltage. The noise components add randomly - as power. Doing this in the frequency domain requires you know what is signal and what is noise and appropriately add power or voltage. And that varies with the mode. The energy in the selected passband is a constant. And it is the term that goes into BER calculations for digital modulation schemes.

If I take the spectral components of an FM signal and add them all up treating them the same as noise then there is no gain that comes out of the coherency of the signal, there is no trade-off between bandwidth and SNR. So I don't see how you can simply add up power in a collection of FFT bins to get an accurate power reading. Please elucidate.

{^_^}

On 20210706 00:12:17, Simon Brown wrote:

Hi,

 

I don’t care about the demodulator, signal strength is just frequency domain stuff. Doesn’t matter what you do with the IQ.

 

Simon Brown, G4ELI

https://www.sdr-radio.com

 

From: main@SDR-Radio.groups.io <main@SDR-Radio.groups.io> On Behalf Of jdow
Sent: 06 July 2021 07:49
To: main@SDR-Radio.groups.io
Subject: Re: [SDR-Radio] SNR meter, bandwidth and gain adjustment for transverters

 

I'd need to see math that proves this is the way to handle coherent sidebands as opposed to summing a large number of complex numbers in pairs of matching sidebands. Are you doing something such that no filtered I and Q value is ever present before the demodulator? That is where it's automatic you get the right value.

{o.o}

On 20210705 23:27:05, Simon Brown wrote:

Hi,

 

Frequency, so using the FFT output. The FFT output is in dBm (log10), so has to be converted back from dB using pow(), averaged and then converted back to dB using log10. This is trivial, doesn’t use much CPU at all.

 

Simon Brown, G4ELI

https://www.sdr-radio.com

 

From: main@SDR-Radio.groups.io <main@SDR-Radio.groups.io> On Behalf Of jdow
Sent: 06 July 2021 07:03
To: main@SDR-Radio.groups.io
Subject: Re: [SDR-Radio] SNR meter, bandwidth and gain adjustment for transverters

 

Averaging across frequency or time? Across frequency summation is perhaps closer, particularly if you presume it's all noise and simply add power per bin. But with coherent sidebands on a signal you can get surprised simply adding power I suspect. Alas, I do not KNOW that. I figure it's easier to do the I^2 + Q^2 operation on the IF before the demodulator. With that signal and something a bit like your noise averaging the signal strength reading and noise reading could actually help you know if there is enough signal to expect your demodulator to provide something understandable, especially for digital modulation schemes. (I'd take your minimum 10% data, sum the powers (I^2+Q^2) in each bin, divide by number of bins, and multiply back by number of bins in the filter bandwidth to get the noise power estimate. That last could probably be reduced to something close to a constant multiply operation.) This makes WGN environments quite predictable. Other environments suffer in comparison. So if the calculation above gives too low an SNR, or value converted to Eb/N0 is too low, then you know a digital mode is not even worth trying. Of it is high enough you know you have a sporting chance.

{^_^}


On 20210705 22:46:33, Simon Brown wrote:

FM power is always constant, this *could* be an area for an averaging signal meter.

 

I’m slowly losing the will to live 😊 .

 

Simon Brown, G4ELI

https://www.sdr-radio.com

 

From: main@SDR-Radio.groups.io <main@SDR-Radio.groups.io> On Behalf Of oldjackbob@...
Sent: 06 July 2021 02:47
To: main@SDR-Radio.groups.io
Subject: Re: [SDR-Radio] SNR meter, bandwidth and gain adjustment for transverters

 

[Edited Message Follows]
[Reason: Initial send occurred for seemingly no reason.]

Joanne,

I probably misspoke at some point if/when I said BCFM carrier is always the greatest power anywhee in teh passband, so I retract any such statement.

However, that statement does hold true for BCAM, so I've captured a video of SDRC's S-meter reporting on a BCAM station:

https://drive.google.com/file/d/1Egb4DyIxXtZNP6rNNKg5PLfQzFTH_7zI/view?usp=sharing

Several key observations:

1) The carrier is very steady.
2) The modulation varies greatly.
3) the passband is intentionally varied between 2.5k and 12k.
4) The S-meter never varies at all (at least not more than .1dB in any direction).
5) The S-meter is reporting ONLY the peak signal detected anywhere in the passband, nothing more and nothing less.

So tell me where Simon gets it wrong.

Nevermind, that's a loaded question...Simon gets it right.

I'm done here,
Mark


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Re: SAQ 17.2 kHz QRV today

Allan Isaacs
 

 

This was written a few years ago using my soundcard om.

http://www.radiomuseum.co.uk/vlf.html (complete with a recording!)

Simon’s come a long way since then and SDRs are a tad bit better than the SAQ receiver.

Of course nothing can beat a real receiver with a proper tuning knob and a jack socket for headphones (and a proper S-Meter).

Except perhaps my first venture… a crystal set in a matchbox connected to a pair of high impedance headphones and a really long wire.

Allan G3PIY

 


From: main@SDR-Radio.groups.io [mailto:main@SDR-Radio.groups.io] On Behalf Of PE1OSQ
Sent: 06 July 2021 00:26
To: main@SDR-Radio.groups.io
Subject: Re: [SDR-Radio] SAQ 17.2 kHz QRV today

 

Re-

Oh how nice it would be if Simons program would support VLF reception via soundcards
in this way.
The picture below is a screenshot of SAQ Panoramic Receiver playing back the RF recording (0-96kHz)

Note: the GREEN line is the RF spectrum. One of the peaks on the right is DCF. The WHITE (actually BLUE)
line is the audio spectrum. No waterfall.

_._,_._,_

 


Re: SAQ 17.2 kHz QRV today

Alan G4ZFQ
 

Gisle,

Google "SAQ Panoramic Receiver (v0.98)" gets a top link http://www.dl1dbc.net/SAQ/

Alan


Re: SNR meter, bandwidth and gain adjustment for transverters

Simon Brown
 

Hi,

 

I don’t care about the demodulator, signal strength is just frequency domain stuff. Doesn’t matter what you do with the IQ.

 

Simon Brown, G4ELI

https://www.sdr-radio.com

 

From: main@SDR-Radio.groups.io <main@SDR-Radio.groups.io> On Behalf Of jdow
Sent: 06 July 2021 07:49
To: main@SDR-Radio.groups.io
Subject: Re: [SDR-Radio] SNR meter, bandwidth and gain adjustment for transverters

 

I'd need to see math that proves this is the way to handle coherent sidebands as opposed to summing a large number of complex numbers in pairs of matching sidebands. Are you doing something such that no filtered I and Q value is ever present before the demodulator? That is where it's automatic you get the right value.

{o.o}

On 20210705 23:27:05, Simon Brown wrote:

Hi,

 

Frequency, so using the FFT output. The FFT output is in dBm (log10), so has to be converted back from dB using pow(), averaged and then converted back to dB using log10. This is trivial, doesn’t use much CPU at all.

 

Simon Brown, G4ELI

https://www.sdr-radio.com

 

From: main@SDR-Radio.groups.io <main@SDR-Radio.groups.io> On Behalf Of jdow
Sent: 06 July 2021 07:03
To: main@SDR-Radio.groups.io
Subject: Re: [SDR-Radio] SNR meter, bandwidth and gain adjustment for transverters

 

Averaging across frequency or time? Across frequency summation is perhaps closer, particularly if you presume it's all noise and simply add power per bin. But with coherent sidebands on a signal you can get surprised simply adding power I suspect. Alas, I do not KNOW that. I figure it's easier to do the I^2 + Q^2 operation on the IF before the demodulator. With that signal and something a bit like your noise averaging the signal strength reading and noise reading could actually help you know if there is enough signal to expect your demodulator to provide something understandable, especially for digital modulation schemes. (I'd take your minimum 10% data, sum the powers (I^2+Q^2) in each bin, divide by number of bins, and multiply back by number of bins in the filter bandwidth to get the noise power estimate. That last could probably be reduced to something close to a constant multiply operation.) This makes WGN environments quite predictable. Other environments suffer in comparison. So if the calculation above gives too low an SNR, or value converted to Eb/N0 is too low, then you know a digital mode is not even worth trying. Of it is high enough you know you have a sporting chance.

{^_^}


On 20210705 22:46:33, Simon Brown wrote:

FM power is always constant, this *could* be an area for an averaging signal meter.

 

I’m slowly losing the will to live 😊 .

 

Simon Brown, G4ELI

https://www.sdr-radio.com

 

From: main@SDR-Radio.groups.io <main@SDR-Radio.groups.io> On Behalf Of oldjackbob@...
Sent: 06 July 2021 02:47
To: main@SDR-Radio.groups.io
Subject: Re: [SDR-Radio] SNR meter, bandwidth and gain adjustment for transverters

 

[Edited Message Follows]
[Reason: Initial send occurred for seemingly no reason.]

Joanne,

I probably misspoke at some point if/when I said BCFM carrier is always the greatest power anywhee in teh passband, so I retract any such statement.

However, that statement does hold true for BCAM, so I've captured a video of SDRC's S-meter reporting on a BCAM station:

https://drive.google.com/file/d/1Egb4DyIxXtZNP6rNNKg5PLfQzFTH_7zI/view?usp=sharing

Several key observations:

1) The carrier is very steady.
2) The modulation varies greatly.
3) the passband is intentionally varied between 2.5k and 12k.
4) The S-meter never varies at all (at least not more than .1dB in any direction).
5) The S-meter is reporting ONLY the peak signal detected anywhere in the passband, nothing more and nothing less.

So tell me where Simon gets it wrong.

Nevermind, that's a loaded question...Simon gets it right.

I'm done here,
Mark


--

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Please use https://forum.sdr-radio.com:4499/ when posting questions or problems.

 


--

- + - + -

Please use https://forum.sdr-radio.com:4499/ when posting questions or problems.

 


--
- + - + -
Please use https://forum.sdr-radio.com:4499/ when posting questions or problems.


Re: SNR meter, bandwidth and gain adjustment for transverters

jdow
 

I'd need to see math that proves this is the way to handle coherent sidebands as opposed to summing a large number of complex numbers in pairs of matching sidebands. Are you doing something such that no filtered I and Q value is ever present before the demodulator? That is where it's automatic you get the right value.

{o.o}

On 20210705 23:27:05, Simon Brown wrote:

Hi,

 

Frequency, so using the FFT output. The FFT output is in dBm (log10), so has to be converted back from dB using pow(), averaged and then converted back to dB using log10. This is trivial, doesn’t use much CPU at all.

 

Simon Brown, G4ELI

https://www.sdr-radio.com

 

From: main@SDR-Radio.groups.io <main@SDR-Radio.groups.io> On Behalf Of jdow
Sent: 06 July 2021 07:03
To: main@SDR-Radio.groups.io
Subject: Re: [SDR-Radio] SNR meter, bandwidth and gain adjustment for transverters

 

Averaging across frequency or time? Across frequency summation is perhaps closer, particularly if you presume it's all noise and simply add power per bin. But with coherent sidebands on a signal you can get surprised simply adding power I suspect. Alas, I do not KNOW that. I figure it's easier to do the I^2 + Q^2 operation on the IF before the demodulator. With that signal and something a bit like your noise averaging the signal strength reading and noise reading could actually help you know if there is enough signal to expect your demodulator to provide something understandable, especially for digital modulation schemes. (I'd take your minimum 10% data, sum the powers (I^2+Q^2) in each bin, divide by number of bins, and multiply back by number of bins in the filter bandwidth to get the noise power estimate. That last could probably be reduced to something close to a constant multiply operation.) This makes WGN environments quite predictable. Other environments suffer in comparison. So if the calculation above gives too low an SNR, or value converted to Eb/N0 is too low, then you know a digital mode is not even worth trying. Of it is high enough you know you have a sporting chance.

{^_^}

On 20210705 22:46:33, Simon Brown wrote:

FM power is always constant, this *could* be an area for an averaging signal meter.

 

I’m slowly losing the will to live 😊 .

 

Simon Brown, G4ELI

https://www.sdr-radio.com

 

From: main@SDR-Radio.groups.io <main@SDR-Radio.groups.io> On Behalf Of oldjackbob@...
Sent: 06 July 2021 02:47
To: main@SDR-Radio.groups.io
Subject: Re: [SDR-Radio] SNR meter, bandwidth and gain adjustment for transverters

 

[Edited Message Follows]
[Reason: Initial send occurred for seemingly no reason.]

Joanne,

I probably misspoke at some point if/when I said BCFM carrier is always the greatest power anywhee in teh passband, so I retract any such statement.

However, that statement does hold true for BCAM, so I've captured a video of SDRC's S-meter reporting on a BCAM station:

https://drive.google.com/file/d/1Egb4DyIxXtZNP6rNNKg5PLfQzFTH_7zI/view?usp=sharing

Several key observations:

1) The carrier is very steady.
2) The modulation varies greatly.
3) the passband is intentionally varied between 2.5k and 12k.
4) The S-meter never varies at all (at least not more than .1dB in any direction).
5) The S-meter is reporting ONLY the peak signal detected anywhere in the passband, nothing more and nothing less.

So tell me where Simon gets it wrong.

Nevermind, that's a loaded question...Simon gets it right.

I'm done here,
Mark


--

- + - + -

Please use https://forum.sdr-radio.com:4499/ when posting questions or problems.

 


--
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Please use https://forum.sdr-radio.com:4499/ when posting questions or problems.


Re: SAQ 17.2 kHz QRV today

Gisle Vanem
 

On Tue, Jul 6, 2021 at 01:25 AM, PE1OSQ wrote:

To receive SAQ I used a free Windows program called SAQ Panoramic Receiver (v0.98).

Where did you get v0.98 from?

I found v0.94 here: https://sites.google.com/site/swljo30tb/home/files


Re: SNR meter, bandwidth and gain adjustment for transverters

Simon Brown
 

Hi,

 

Frequency, so using the FFT output. The FFT output is in dBm (log10), so has to be converted back from dB using pow(), averaged and then converted back to dB using log10. This is trivial, doesn’t use much CPU at all.

 

Simon Brown, G4ELI

https://www.sdr-radio.com

 

From: main@SDR-Radio.groups.io <main@SDR-Radio.groups.io> On Behalf Of jdow
Sent: 06 July 2021 07:03
To: main@SDR-Radio.groups.io
Subject: Re: [SDR-Radio] SNR meter, bandwidth and gain adjustment for transverters

 

Averaging across frequency or time? Across frequency summation is perhaps closer, particularly if you presume it's all noise and simply add power per bin. But with coherent sidebands on a signal you can get surprised simply adding power I suspect. Alas, I do not KNOW that. I figure it's easier to do the I^2 + Q^2 operation on the IF before the demodulator. With that signal and something a bit like your noise averaging the signal strength reading and noise reading could actually help you know if there is enough signal to expect your demodulator to provide something understandable, especially for digital modulation schemes. (I'd take your minimum 10% data, sum the powers (I^2+Q^2) in each bin, divide by number of bins, and multiply back by number of bins in the filter bandwidth to get the noise power estimate. That last could probably be reduced to something close to a constant multiply operation.) This makes WGN environments quite predictable. Other environments suffer in comparison. So if the calculation above gives too low an SNR, or value converted to Eb/N0 is too low, then you know a digital mode is not even worth trying. Of it is high enough you know you have a sporting chance.

{^_^}

On 20210705 22:46:33, Simon Brown wrote:

FM power is always constant, this *could* be an area for an averaging signal meter.

 

I’m slowly losing the will to live 😊 .

 

Simon Brown, G4ELI

https://www.sdr-radio.com

 

From: main@SDR-Radio.groups.io <main@SDR-Radio.groups.io> On Behalf Of oldjackbob@...
Sent: 06 July 2021 02:47
To: main@SDR-Radio.groups.io
Subject: Re: [SDR-Radio] SNR meter, bandwidth and gain adjustment for transverters

 

[Edited Message Follows]
[Reason: Initial send occurred for seemingly no reason.]

Joanne,

I probably misspoke at some point if/when I said BCFM carrier is always the greatest power anywhee in teh passband, so I retract any such statement.

However, that statement does hold true for BCAM, so I've captured a video of SDRC's S-meter reporting on a BCAM station:

https://drive.google.com/file/d/1Egb4DyIxXtZNP6rNNKg5PLfQzFTH_7zI/view?usp=sharing

Several key observations:

1) The carrier is very steady.
2) The modulation varies greatly.
3) the passband is intentionally varied between 2.5k and 12k.
4) The S-meter never varies at all (at least not more than .1dB in any direction).
5) The S-meter is reporting ONLY the peak signal detected anywhere in the passband, nothing more and nothing less.

So tell me where Simon gets it wrong.

Nevermind, that's a loaded question...Simon gets it right.

I'm done here,
Mark


--

- + - + -

Please use https://forum.sdr-radio.com:4499/ when posting questions or problems.

 


--
- + - + -
Please use https://forum.sdr-radio.com:4499/ when posting questions or problems.


Re: SNR meter, bandwidth and gain adjustment for transverters

jdow
 

Averaging across frequency or time? Across frequency summation is perhaps closer, particularly if you presume it's all noise and simply add power per bin. But with coherent sidebands on a signal you can get surprised simply adding power I suspect. Alas, I do not KNOW that. I figure it's easier to do the I^2 + Q^2 operation on the IF before the demodulator. With that signal and something a bit like your noise averaging the signal strength reading and noise reading could actually help you know if there is enough signal to expect your demodulator to provide something understandable, especially for digital modulation schemes. (I'd take your minimum 10% data, sum the powers (I^2+Q^2) in each bin, divide by number of bins, and multiply back by number of bins in the filter bandwidth to get the noise power estimate. That last could probably be reduced to something close to a constant multiply operation.) This makes WGN environments quite predictable. Other environments suffer in comparison. So if the calculation above gives too low an SNR, or value converted to Eb/N0 is too low, then you know a digital mode is not even worth trying. Of it is high enough you know you have a sporting chance.

{^_^}

On 20210705 22:46:33, Simon Brown wrote:

FM power is always constant, this *could* be an area for an averaging signal meter.

 

I’m slowly losing the will to live 😊 .

 

Simon Brown, G4ELI

https://www.sdr-radio.com

 

From: main@SDR-Radio.groups.io <main@SDR-Radio.groups.io> On Behalf Of oldjackbob@...
Sent: 06 July 2021 02:47
To: main@SDR-Radio.groups.io
Subject: Re: [SDR-Radio] SNR meter, bandwidth and gain adjustment for transverters

 

[Edited Message Follows]
[Reason: Initial send occurred for seemingly no reason.]

Joanne,

I probably misspoke at some point if/when I said BCFM carrier is always the greatest power anywhee in teh passband, so I retract any such statement.

However, that statement does hold true for BCAM, so I've captured a video of SDRC's S-meter reporting on a BCAM station:

https://drive.google.com/file/d/1Egb4DyIxXtZNP6rNNKg5PLfQzFTH_7zI/view?usp=sharing

Several key observations:

1) The carrier is very steady.
2) The modulation varies greatly.
3) the passband is intentionally varied between 2.5k and 12k.
4) The S-meter never varies at all (at least not more than .1dB in any direction).
5) The S-meter is reporting ONLY the peak signal detected anywhere in the passband, nothing more and nothing less.

So tell me where Simon gets it wrong.

Nevermind, that's a loaded question...Simon gets it right.

I'm done here,
Mark


--
- + - + -
Please use https://forum.sdr-radio.com:4499/ when posting questions or problems.


Re: SNR meter, bandwidth and gain adjustment for transverters

Simon Brown
 

FM power is always constant, this *could* be an area for an averaging signal meter.

 

I’m slowly losing the will to live 😊 .

 

Simon Brown, G4ELI

https://www.sdr-radio.com

 

From: main@SDR-Radio.groups.io <main@SDR-Radio.groups.io> On Behalf Of oldjackbob@...
Sent: 06 July 2021 02:47
To: main@SDR-Radio.groups.io
Subject: Re: [SDR-Radio] SNR meter, bandwidth and gain adjustment for transverters

 

[Edited Message Follows]
[Reason: Initial send occurred for seemingly no reason.]

Joanne,

I probably misspoke at some point if/when I said BCFM carrier is always the greatest power anywhee in teh passband, so I retract any such statement.

However, that statement does hold true for BCAM, so I've captured a video of SDRC's S-meter reporting on a BCAM station:

https://drive.google.com/file/d/1Egb4DyIxXtZNP6rNNKg5PLfQzFTH_7zI/view?usp=sharing

Several key observations:

1) The carrier is very steady.
2) The modulation varies greatly.
3) the passband is intentionally varied between 2.5k and 12k.
4) The S-meter never varies at all (at least not more than .1dB in any direction).
5) The S-meter is reporting ONLY the peak signal detected anywhere in the passband, nothing more and nothing less.

So tell me where Simon gets it wrong.

Nevermind, that's a loaded question...Simon gets it right.

I'm done here,
Mark


--
- + - + -
Please use https://forum.sdr-radio.com:4499/ when posting questions or problems.


Re: SNR meter, bandwidth and gain adjustment for transverters

Simon Brown
 

Nope,

Continuum mode is similar to what's being request here I think, it's used in
radio astronomy and supported in SpectraVue.

http://www.rfspace.com/RFSPACE/Astronomy.html

It really is a real thing.

Simon Brown, G4ELI
https://www.sdr-radio.com

-----Original Message-----
From: main@SDR-Radio.groups.io <main@SDR-Radio.groups.io> On Behalf Of Bob
Dengler
Sent: 06 July 2021 00:07
To: main@SDR-Radio.groups.io
Subject: Re: [SDR-Radio] SNR meter, bandwidth and gain adjustment for
transverters

At 7/5/2021 03:28 PM, you wrote:
WTFF is "Continuum mode". You are losing your audience by inventing terms
that make no sense. Do you mean time domain where everything flows along in
a sampled stream? If so then time domain makes more sense to the engineers
designing things. It's instantly understandable. {+_+}

I thought perhaps he was referring to omnipotent signals.

-Q










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Re: S Meters

Curt Faulk
 

Hi, Simon:

A typo crept in when we weren't looking...

SNR
And here's a Signal to Noise (SNR) meter. When observing what may appear to be just background noise you will typically see a level of ~8dB SNR. This is because the noise floor value is the mean (average) of the noise, but the noise itself will not be constant. If you don't belive this, just watch the S Meter of a traditional radio on what appears to be a quiet band.


Re: SNR meter, bandwidth and gain adjustment for transverters

jdow
 

S-Meter specifics - I sure as HELL have been specific, twit. It should be derived from the power within the IF passband not from one potentially tiny spectral component. It is a signal strength measurement. That is a power measurement not a partial power measurement.
{+_+}

On 20210705 19:57:20, oldjackbob@... wrote:
On Mon, Jul 5, 2021 at 07:18 PM, jdow wrote:
SDRC's S-Meter is NOT a proper measurement. It is a usable measurement. But you cannot use it to calculate signal quality in a precise manner. It is CERTAINLY not correct to the IARU definition. He may use the correct attack and decay times on the meter; but, he is not working off the power in the passband.
You're expecting the S-meter to be something it's not. It's not intended to "calculate signal quality in a precise manner", nor is it intended to "work off the power in the passband".

The S-meter is by definition intended to report the highest voltage measured anywhere in the passband. Per IARU Region 1 Technical Recommendation R.1, a signal strength of 50 microvolts is designated as S9 (which correlates to a -73dBm power level assuming an input impedance of 50 ohms) for the HF bands.

Nowhere in the IARU Region 1 spec (or any other document) is "calculation of signal quality" or "total power in the passband" mentioned at all. So someone looking for a "quality of signal" meter would probably be better off just wishing in one hand and...

You keep saying that Simon isn't conforming to the spec but you never offer any specifics. So I'm done with your nonsense (and your meanness) too.

And one more thing - notice how I always sign my name, and you never do, Joanne (and I'm probably spelling it wrong, but there's no way to know because you never sign).

Mark



Re: SNR meter, bandwidth and gain adjustment for transverters

jdow
 

I put in a signature from time to time. I've used that glyph so much I usually forget to put a name on it. This comes from being stalked online, for a year, back in 1985. I was issued threats of gruesom rapes and deaths. I stuck it out. He ended up suiciding a fe years later. I'm still here and mostly anonymous as a result. Once Was Enough. (I carried a loaded and ready double action revolver for much of that year. My purse was heavier. The hope was that I'd be the one to come out alive if we ever met in person. It left me - scarred at the least.)

{^_^}   Joanne

On 20210705 19:57:20, oldjackbob@... wrote:
On Mon, Jul 5, 2021 at 07:18 PM, jdow wrote:
SDRC's S-Meter is NOT a proper measurement. It is a usable measurement. But you cannot use it to calculate signal quality in a precise manner. It is CERTAINLY not correct to the IARU definition. He may use the correct attack and decay times on the meter; but, he is not working off the power in the passband.
You're expecting the S-meter to be something it's not. It's not intended to "calculate signal quality in a precise manner", nor is it intended to "work off the power in the passband".

The S-meter is by definition intended to report the highest voltage measured anywhere in the passband. Per IARU Region 1 Technical Recommendation R.1, a signal strength of 50 microvolts is designated as S9 (which correlates to a -73dBm power level assuming an input impedance of 50 ohms) for the HF bands.

Nowhere in the IARU Region 1 spec (or any other document) is "calculation of signal quality" or "total power in the passband" mentioned at all. So someone looking for a "quality of signal" meter would probably be better off just wishing in one hand and...

You keep saying that Simon isn't conforming to the spec but you never offer any specifics. So I'm done with your nonsense (and your meanness) too.

And one more thing - notice how I always sign my name, and you never do, Joanne (and I'm probably spelling it wrong, but there's no way to know because you never sign).

Mark



Re: SNR meter, bandwidth and gain adjustment for transverters

Mark Cayton
 

On Mon, Jul 5, 2021 at 07:18 PM, jdow wrote:
SDRC's S-Meter is NOT a proper measurement. It is a usable measurement. But you cannot use it to calculate signal quality in a precise manner. It is CERTAINLY not correct to the IARU definition. He may use the correct attack and decay times on the meter; but, he is not working off the power in the passband.
You're expecting the S-meter to be something it's not. It's not intended to "calculate signal quality in a precise manner", nor is it intended to "work off the power in the passband".

The S-meter is by definition intended to report the highest voltage measured anywhere in the passband. Per IARU Region 1 Technical Recommendation R.1, a signal strength of 50 microvolts is designated as S9 (which correlates to a -73dBm power level assuming an input impedance of 50 ohms) for the HF bands.

Nowhere in the IARU Region 1 spec (or any other document) is "calculation of signal quality" or "total power in the passband" mentioned at all. So someone looking for a "quality of signal" meter would probably be better off just wishing in one hand and...

You keep saying that Simon isn't conforming to the spec but you never offer any specifics. So I'm done with your nonsense (and your meanness) too.

And one more thing - notice how I always sign my name, and you never do, Joanne (and I'm probably spelling it wrong, but there's no way to know because you never sign).

Mark


Re: SNR meter, bandwidth and gain adjustment for transverters

jdow
 

Pardon me - 1/2 that number of dB, 1.7609125905568124208128900853062 dB.
{^_^}

On 20210705 19:18:19, jdow wrote:
You do not get it. I can see that clearly, Actually the total power in a 100% modulated pure AM signal is about 3.5218251811136248416257801706124 dB greater than the carrier power alone. (Some perversions allow larger excursions by raising the transmitter's power briefly during signal peaks. That's a cheat.)

The TOTAL power in the bandwidth is what builds your signal plus noise plus distortion reading. That said, no known AM receiver, except (holds her hand up), measures the signal in a manner such as to show this. Diode detectors definitely do not show it. Theory shows it. Spectral analysis shows it. But the simple demodulators do not.

You are trying to hit a special case that matches your view of the picture. SDRC's S-Meter is NOT a proper measurement. It is a usable measurement. But you cannot use it to calculate signal quality in a precise manner. It is CERTAINLY not correct to the IARU definition. He may use the correct attack and decay times on the meter; but, he is not working off the power in the passband. You can see this very dramatically with FM. When the signal to noise ratio falls below 9 dB the signal degrades VERY rapidly. With his S-Meter arrangement that number will be very different.

To be meaningful he must collect all the energy within the receiver passband paying attention to phase as well as amplitude. I've shown the simple way. His way gives results at odds with reality in many edge cases, some of which I see frequently.

(If somebody asks me for a signal report it is always, "59 solid copy, Good Buddy." The tone of voice probably clues some in to the fact that it's a canned response.)

{o.o}

On 20210705 18:47:10, oldjackbob@... wrote:
Joanne,

I probably misspoke at some point if/when I said BCFM carrier is always the greatest power anywhee in teh passband, so I retract any such statement.

However, that statement does hold true for BCAM, so I've captured a video of SDRC's S-meter reporting on a BCAM station:

https://drive.google.com/file/d/1Egb4DyIxXtZNP6rNNKg5PLfQzFTH_7zI/view?usp=sharing

Several key observations:

1) The carrier is very steady.
2) The modulation varies greatly.
3) the passband is intentionally varied between  



Re: SNR meter, bandwidth and gain adjustment for transverters

jdow
 

Make taht four.
{+_+}

On 20210705 18:47:10, oldjackbob@... wrote:

[Edited Message Follows]

Joanne,

I probably misspoke at some point if/when I said BCFM carrier is always the greatest power anywhere in the passband, so I retract any such statement.

However, that statement does hold true for BCAM, so I've captured a video of SDRC's S-meter reporting on a BCAM station:

https://drive.google.com/file/d/1Egb4DyIxXtZNP6rNNKg5PLfQzFTH_7zI/view?usp=sharing

Several key observations:

1) The carrier is very steady.
2) The modulation varies greatly.
3) The passband is intentionally varied between 2.5k and 12k.
4) The S-meter never varies at all (at least not more than .1dB in any direction).
5) The S-meter is reporting ONLY the peak signal detected anywhere in the passband, nothing more and nothing less.

So tell me where Simon gets it wrong.

Nevermind, that's a loaded question...Simon gets it right.

I'm done here,
Mark


Re: SNR meter, bandwidth and gain adjustment for transverters

jdow
 

All three copies are wrong.
{^_^}

On 20210705 18:47:10, oldjackbob@... wrote:

[Edited Message Follows]
[Reason: Punctuation]

Joanne,

I probably misspoke at some point if/when I said BCFM carrier is always the greatest power anywhee in teh passband, so I retract any such statement.

However, that statement does hold true for BCAM, so I've captured a video of SDRC's S-meter reporting on a BCAM station:

https://drive.google.com/file/d/1Egb4DyIxXtZNP6rNNKg5PLfQzFTH_7zI/view?usp=sharing

Several key observations:

1) The carrier is very steady.
2) The modulation varies greatly.
3) The passband is intentionally varied between 2.5k and 12k.
4) The S-meter never varies at all (at least not more than .1dB in any direction).
5) The S-meter is reporting ONLY the peak signal detected anywhere in the passband, nothing more and nothing less.

So tell me where Simon gets it wrong.

Nevermind, that's a loaded question...Simon gets it right.

I'm done here,
Mark


Re: SNR meter, bandwidth and gain adjustment for transverters

jdow
 



On 20210705 18:47:10, oldjackbob@... wrote:
I'm done here,
Mark
Fortunately - I am about to become persona non-grata over this nonsense from you.

{+_+}


Re: SNR meter, bandwidth and gain adjustment for transverters

jdow
 

You do not get it. I can see that clearly, Actually the total power in a 100% modulated pure AM signal is about 3.5218251811136248416257801706124 dB greater than the carrier power alone. (Some perversions allow larger excursions by raising the transmitter's power briefly during signal peaks. That's a cheat.)

The TOTAL power in the bandwidth is what builds your signal plus noise plus distortion reading. That said, no known AM receiver, except (holds her hand up), measures the signal in a manner such as to show this. Diode detectors definitely do not show it. Theory shows it. Spectral analysis shows it. But the simple demodulators do not.

You are trying to hit a special case that matches your view of the picture. SDRC's S-Meter is NOT a proper measurement. It is a usable measurement. But you cannot use it to calculate signal quality in a precise manner. It is CERTAINLY not correct to the IARU definition. He may use the correct attack and decay times on the meter; but, he is not working off the power in the passband. You can see this very dramatically with FM. When the signal to noise ratio falls below 9 dB the signal degrades VERY rapidly. With his S-Meter arrangement that number will be very different.

To be meaningful he must collect all the energy within the receiver passband paying attention to phase as well as amplitude. I've shown the simple way. His way gives results at odds with reality in many edge cases, some of which I see frequently.

(If somebody asks me for a signal report it is always, "59 solid copy, Good Buddy." The tone of voice probably clues some in to the fact that it's a canned response.)

{o.o}

On 20210705 18:47:10, oldjackbob@... wrote:
Joanne,

I probably misspoke at some point if/when I said BCFM carrier is always the greatest power anywhee in teh passband, so I retract any such statement.

However, that statement does hold true for BCAM, so I've captured a video of SDRC's S-meter reporting on a BCAM station:

https://drive.google.com/file/d/1Egb4DyIxXtZNP6rNNKg5PLfQzFTH_7zI/view?usp=sharing

Several key observations:

1) The carrier is very steady.
2) The modulation varies greatly.
3) the passband is intentionally varied between  


Re: SNR meter, bandwidth and gain adjustment for transverters

jdow
 

This is why I loved working on GPS, almost the quintessence of time keeping. It's the best answer most people can afford.

{o.o}

On 20210705 18:46:30, Curt Faulk wrote:
Joanne:

I just love your rants. I love them because I'm usually learning quite a bit as I read them.

You provide immeasurable benefit to us all.  I know how much It must pain you to hear me say that... because it is exceedingly apparent how much you like quantifiable measurements.

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