Hello Matthias,
Your measurements and assumptions seem plausible to me.
I am using an Octagon LNB in an 85cm offset dish and also SDR console as software.
Today I measured the following data:
CW beacon signal strength: -52,0 dBm
Average noise: -84,4 dBm,
so the SNR was 32,4 dBm today.
My own signal (1 Watt output into a 1 Meter prime-focus dish, fed with a 5 1/4 turn helical) has 28 dBm (signal strength 56,3 dBm), which seems plausible, too.
Best 73
Holger ‘Geri’, DK8KW
Got 28dB here on the CW beacon, SDR-Console (3.07) as well. Do you use the signal history to get the readings?
abt 34-35db over nbtp floor here, 130cms gibertini dish+octagon lnb
HDSDR, with 4 times averaging and RBW 14,6Hz
I used the SDR Console signal history to determine the data.
vy 73
Holger, DK8KW
Here 1 mt dish + octagon LNB
80cm dish, unmodified Octagon OSLO, Airspy, SDR#
with SDR# RTL-SDR-V3 
120cm dish, Octagon OSLO GPS, RTL-Stick , SDR#
ciao Lucio,
che software stai usando per produrre quei grafici?
what software are you using?
got 54 dB SNR now..
"But how can this be, you said 28dB before?"
different software(algorithm) and/or settings.. and I think here lies the problem in our wildy varying numbers.
We all know we should quote SNR related to receive BW. So most in the community quote it for a 2500 Hz SSB BW (as like for JT modes and many others). Others (like the amateur-DSN people) use 1 Hz as normalized BW and this is fine as well. The conversion factor is simply 10*log(2500)= 34dB.
Our problem here now is that the different SDR packages we use have wildly different algorithms. Take SDR-Console as example.
- no way of setting FFT bin size manually
- signal history seems to display peak values, not mean
- no direct SNR value given and no explanation of underlying parameters (noise BW?)
SDR# has a SNR meter but they depend on the FFT bin size and sampling rate so no easy measurement possible as well.
Andy Talbot G4JNT has a fine tool for doing such measurements:
http://www.g4jnt.com/SignalToNoiseMon.zip
When I let SDR-Console do the drift correction and route the audio via virtual cable to Andy's software I get 54 dB in 1 Hz for the CW beacon in an 88cm dish.
So i guess 45,3db here? Are the settings correct in the SN-Mon SW?
I am by no means an expert on Andy's software but make sure the sampling rate of the virtual audio cable is correct, also press 'peak to CF' and then another box with metrics should come up in the bottom right corner (your center frequency is way off). Still digging through the manual myself but numbers are converging now.
It seems that my pc is to slow for a quick lock on the signal, sometimes in the right bottom of the window some numbers show up and then disappear again.
Also it only locks in the two short periods when the beacon is constantly transmitting.
But if we find a "standard" way to measure the beacon sig to the noise with this nice program it could give us a good way to compare our rx systems.
I believe this is a 'feature' of the program. No signal peak, no SNR measurement. But with the correct settings, the readings in the constant-on periods are fairly reproducible.
I also am no expert in this matter. I'm using a 1.2m Gilbertini offset dish Octogon LNB and a LimeSDR mini here and measuring the CW beacon using SDR Console I get 34dB on the steady carrier and 84dB @ 1 Hz and 49dB @ 2.5kHz using Andy's software.
Flo is correct, it would be good to use and "independant" piece of software such as Andy's to compare results across the many different configurations being used on QO-100. Time to read the manual 
84dB in 1 Hz is technically not possible with the transponder.. have you set the sampling rate correctly in G4JNT's software?
