Re: SDR-Console Power dBm Accuracy


Gedas
 

Hi Larry. Have you considered deriving the NF from the MDS ? This is quite repeatable and accurate for detection systems that do not have extremely low NF's.

The same caveats apply requiring a calibrated sig gen and external step attenuator(s) with a calibrated true reading RMS meter. Commonly done in my past life in tempest engineering.

I generated a simple Youtube video illustrating the procedure if you think it is applicable to your needs. 73

https://www.youtube.com/watch?v=qPWXbodjVIA

Gedas, W8BYA EN70JT

Gallery at http://w8bya.com (under repair)
Light travels faster than sound....
This is why some people appear bright until you hear them speak.
On 6/23/2021 9:57 PM, Larry Dodd wrote:

jdow,
Thanks. We use a calibrated on/off noise source to do a Y Factor Method for SDR noise figure measurements. I have found just using the spectrum dBm measurements easier than the dBm meter. It usually reads -140 dBm constantly with low noise floors. 
Thanks,
Larry

On Jun 23, 2021, at 9:49 PM, jdow <jdow@...> wrote:

 That's a big subject.

To a first approximation the spectrum is very accurate for differences in reading. It's theoretically perfect if there is a perfect A/D converter involved. The A/D converter's step to step linearity can mess up this theoretically perfect relative calibration.

In any absolute sense any calibration present is rather loosy goosy unless you provide a precision source and take care getting your readings. Otherwise "loosy goosy" can mean +/- 20 dB or worse.

I refuse to address Simon's S-Meter accuracy until I check to see if I can still spoof it.

{^_^}

On 20210623 17:53:16, Larry Dodd wrote:
I have been asked the question, "How accurate are the SDR-Console dBm spectrograph and dBm meter readings?"  Can anyone answer that question? We are interested in measuring the noise floor of various SDR receivers.
Thanks,
Larry, K4LED

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