Re: 116 dB SNR off the back of the 2m beam!


Simon Brown
 

Fine = not causing me any grief when I'm 10kHz away.

When the 'bad boy' is on then we have to stay ~60kHz apart, for next year I'll maybe use an antenna with 12dB more F/B. If the 'bad boy' really gets exactly on the back on my antenna the receiver chain collapses, SNR gets up to 120dB or so then goes 'tits up'. This rarely happens.

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

-----Original Message-----
From: main@SDR-Radio.groups.io <main@SDR-Radio.groups.io> On Behalf Of Conrad, PA5Y
Sent: 02 July 2021 22:41
To: main@SDR-Radio.groups.io
Subject: Re: [SDR-Radio] 116 dB SNR off the back of the 2m beam!

Hello Simon, I am quite used to flogging a dead horse. However if a few of us such as Alwyn Seeds and Rob Sherwood keep going on about transmitters maybe a few people will consider the issues and if I am lucky it could be somebody near me. Of course I appreciate that your experience of VHF in your location is very different from mine. Transceivers are slowly improving and this must be the next marketing topic, receivers are so good these days the manufacturers have nowhere else to make significant improvements.

What you think is fine is quite different to me but you never quantify things so it is very hard to know what 'fine' is. Anyway enough of that I will stop flogging this particular horse.

Now on a slightly different note you please explain to me how the dBm scale shown is derived and how it relates or indeed if it relates in any way to bandwidth? Is it absolute power (probably ADC voltage related to 50 ohm?) Also the SNR meter. I see 12dB SNR when there is no signal present, why is that? I would like to understand. How come the SNR meter reading does not change as I change filter bandwidth? I can hear with good old fashioned lug 'oles that the SNR is improving.

For sun noise, composite noise and a few other things I use my Perseus with various frequency converters. The Perseus is still an excellent SDR and very useful for this. In Linrad I can set a gain offset which maybe based upon a real signal, this then takes care of any gain offset in the frequency converter. It will also read dBm/Hz based upon the RMS or peak in the selected bandwidth. This is very nice but would be much better with your UI! Maybe I can enter this offset somewhere but I could not find it.

I do not see any changes in reported power (I know its a voltage but power in 50 ohm) related to BW. It would be nice to have this.

I use SDR console as an excellent band-scope in conjunction with my transverter and K3S, I simply split the 28MHz IF. I really like the visuals and the demodulation but these gain and BW settings would be the icing on the cake and make SDR console useful for measurements.

Just a thought.

Regards

Conrad PA5Y










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