Noise level reading

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Patrick73
Posts: 25
Joined: Thu May 31, 2018 9:39 am

Noise level reading

Postby Patrick73 » Thu Jul 12, 2018 2:19 pm

Hi there !

I'm tuned to the 2m band and my SDRuno reads abt -125 dBm on a 'clear' frequency (using a 4 elts Yagi, FM mode, 9 kHz filter).
Could someone explain in simple words why, in the spectro, the noise floor shows abt 145-150 dBm ? What is measured there ?

Thanks.
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glovisol
Posts: 115
Joined: Thu May 10, 2018 6:42 pm
Location: Piedmont, Italy

Re: Noise level reading

Postby glovisol » Thu Jul 12, 2018 4:39 pm

PSE read thread on low noise operation.
Glovisol

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Patrick73
Posts: 25
Joined: Thu May 31, 2018 9:39 am

Re: Noise level reading

Postby Patrick73 » Thu Jul 12, 2018 4:54 pm

That's not the kind of reply I was expecting, but thank you ;-)

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Tech_Support
Posts: 341
Joined: Mon Jun 01, 2015 7:00 pm

Re: Noise level reading

Postby Tech_Support » Thu Jul 12, 2018 5:36 pm

Hello Patrick,
The noise floor on the spectrum display is the noise power per bin of the FFT, or put another way, it is the total noise power in the resolution bandwidth of the FFT. I cannot see the RBW value in your picture, but it will be shown in the lower right hand corner of your SP1 display. The Power meter on the other hand shows the total power within the demodulation bandwidth, which in your case is 9 kHz. The difference between the two values will be 10*Log (9 kHz/RBW)

Sincerely

SDRplay Tech_Support

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Patrick73
Posts: 25
Joined: Thu May 31, 2018 9:39 am

Re: Noise level reading

Postby Patrick73 » Thu Jul 12, 2018 7:51 pm

Thanks for the detailed reply and the formula.

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