SDRplay Community Forum

I think Im doing something wrong, Im receiving booming signals and s-meter reads 5/6, i receive mediocre signals and s-meter reads 5/8..and I scratch my head.

The RSP IFAGC will always try to increase the signal level into the ADC without introducing overload by adjusting the IF gain. When you are looking at different signal levels, look at the gain value in the top right corner of the Main Window to see what the AGC is doing.

Best regards,

Andy

That is why I do not use automatic IF-agc. Mostly setting it on -40 dB manual since I started using SDRplay models. Also its the SNR that is most important. S-meters are just a indication, but offers little value to me. I mostly use a external variable attenuator with 5 dB steps up to 65 dB to avoid overdriving the agc. Also using auto IF-agc bounces the noise base level wich I do not like and you can almost not measure exact signal levels. Ok, it will "protect" the adc in some way, but it is not the ideal solution but its rather a lazy operator approach in my opinion.

Just my 2 cents

We Ham Radio Amateurs call the S-meter a Fun-meter or Lie-detector, just depends if the reading is good or bad for you.
Don't think anything of it, it's just a reading that you can use to compare signals for yourself and nothing else.
Any reading you get has no meaning and also can't be compared to other, sadly many do do compare, but is useless.

It will only indicate if one signal is stronger then the other on your receiver, nothing more.
Also levels are different for different frequencies.

That is the reason the military has stopped using S-readings as many didn't see it for what it is and make too much out of it.

IT IS HIGH TIME OLD FASHIONED AND WRONG MISCONCEPTIONS ABOUT THE "S" METER READINGS WERE PUT TO BED & FORGOTTEN

Here, in the thread below, anyone interested can read about "S" meter readings and equivalence to received power levels in dBm. This thread was initiated (story always repeats itself!) by a guy having little faith in "S" meter readings of the RSP receiver and also contains a detailed comment by Tech_Support:

https://www.sdrplay.com/community/viewt ... ter#p11423

While it is true that in the past "S" meter readings were more a matter of speculation than accurate measurements and this because all communications receivers had, inside the chassis, a pot marked "S METER CAL" that many operators felt free to "calibrate" to their heart's content, in our present times SDRuno with the RSP class Spectrum Processors provide EXTREMELY ACCURATE READINGS OF "S" METER VALUES, for the very simple reason that they already measure and calculate the received power in dBm with an accuracy of better +/- 1 dB. It is therefore very easy to transfer this information to "S" meter readings having the same accuracy.

This performance can be easily proven by anyone possessing a calibrated signal generator and caring to do accurate measurements: furthermore it is this performance which marks the difference brought about by RSP technlogy and we all should do well to be aware of it.

To conclude, NO "S" METER CALIBRATION IS EVER NECESSARY with RSP receivers (provided they are used with SDRuno software) and every operator can rest assured that the "S" meter readings displayed are again accurate to better than +/- 1 dB, while "S" units are organised in 6 dB steps!

glosivol: What you wrote maybe so. But, since receive systems are not calibrated, as ON5HB wrote above

It will only indicate if one signal is stronger then the other on your receiver, nothing more.

Mike2459 wrote:glosivol: What you wrote maybe so. But, since receive systems are not calibrated, as ON5HB wrote above

It will only indicate if one signal is stronger then the other on your receiver, nothing more.

Hi Mike2649, sorry to contradict you and Bas: who says RSP Spectrum Processors are not calibrated? And on what grounds? If I connect (I did) a signal generator to the input of my RSPduo and set the generator to 20 MHz and for 50 uV output or -73 dBm output, the power meter on the SDRuno reads -73 dBm and the SDRuno "S" meter reads S9. If I do the same at 14 MHz, or at 7 MHz I find the same result...... Do you perhaps find otherwise with your RSP? BTW I am glovisol, not glosivol...

Think about it: what would the meaning be of the Power Meter on the SDRplay RSP's if it were to give hapzard readings?

The only thing you measure is the voltage at the input-plug of the receiver.

It doesn't say anything about the signal, antenna-system, cable losses, conditions in the sky, etc.

Also, on HF it's 50μV for S9 but on VHF 5μV, so on VHF you should see a different reading.

But it's just that, a μV number at the plug. Has no meaning other then that.

Sorry about the typo.

Never said anything about haphazard readings. I think Bas said it well enough so I won't repeat it. Except that the RSP's take the VHF+ and HF S-meter standards into account and report the correct S-unit value.

ON5HB wrote:The only thing you measure is the voltage at the input-plug of the receiver.

It doesn't say anything about the signal, antenna-system, cable losses, conditions in the sky, etc.

Also, on HF it's 50μV for S9 but on VHF 5μV, so on VHF you should see a different reading.

But it's just that, a μV number at the plug. Has no meaning other then that.

If I'm not mistaken, the RSP s-meter takes account of that.