3 replies to this topic

[lupus44]

Hello everybody,

 

The bargraph that appears when the Satelitte Pointer is activated shows the SNR, the AGC and the BER, levels. If the SNR is useful, the AGC is not significant of the quality of signal.

Is there another bargraph available in the plug ins, which gives an indication of signal quality, instead of AGC level.

 

Thank you for answer 

 

Lupus
 

[littlesat]

The AGC was never significant... But users get used to it so we cannot remove it...

 

The real parameter for the quality of the signal (the FEC on the correct side of the tuners) is not available in all tuners as far I know. When it was available we could give a bit error value.... a long long long long time ago I made such thing for the DMM7000 (enigma1) which also changed some tuner parameters to increase the quality by fine tuning the tuner. Since the Enigma2 boxes I was never able to reintroduce this mechanism.

 

Shortly saying... we cannot give this information.

 

We can only approx. it by calculating the SNR when it is correctly presented in dB (which is already doubtfully) and the transponder parameters... But due to the SNR (in dB) is already an approx. thing doing it that way is also not helpfully...

Edited by littlesat, 25 July 2018 - 12:52.

[lupus44]

Thank's for that answer, i understand it is not a priority for you. After all, i'll use the indications given by an external Satfinder like the SF-500. It seems to be a good and no too expensive one. I don't need a spectrum analyser .....

 

Have a nice day

[Erik Slagter]

No that is incorrect.

 

The BER-before-FEC, which Littlesat refers to, is data we don't have access to. It's something the tuner knows about, and only the (closed source) driver have access to the tuners and they don't provide this value. So one way or another, we simply cannot provide this information, even though we'd like to.

 

On the other hand, the tuner, the drivers and enigma DO provide the SNR value. The SNR value is directly related to the BER-before-FEC value. More signal quality (= SNR) means less noise, less distortion, less corrupted bits in the demodulated stream (= BER-before-FEC), they have a tight relation to each other. And then finally, the BER value we provide, is the BER after both FEC rounds are applied, and this value should always be "0", perfect stream  = perfect picture.

 

I don't have a clue what you want with the AGC value. AGC = automatic gain control. It's a circuit in the tuner that increases/decreases the initial gain depening on the strength of the signal, to obtain best demodulation. Crudely said it measures the strength of the signal, more signal = less gain = less AGC. There are two reasons why AGC isn't as interesting as it sounds.

 

1) the strength of the signal is not interesting, really. It simply measure the voltage of the signal, including the real signal + all noise and distortions together. It's really easy to amplify any signal level to an acceptable level (which is what AGC does). It won't buy you anything, because all the noise and distortions get equally amplified. A bad signal is a bad signal and remains a bad signal at any level or amplification.

2) most tuner/drivers provide a value that doesn't seem to have any relationship to actual AGC or signal strength.

 

So take my advice, forget about AGC. Use SNR, that's what's it for.

Edited by Erik Slagter, 18 August 2018 - 12:32.