S-meter Vs dbm

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IZ2245SWL
Posts: 6
Joined: Wed Dec 21, 2016 7:09 pm

S-meter Vs dbm

Postby IZ2245SWL » Fri Nov 03, 2017 3:32 pm

Taking as reference the table shown on Wikipedia (https://en.wikipedia.org/wiki/S_meter), I noted a discrepancy between the SP1 dBm scale and S meter reading. The S-meter is 3 S points higher, more or less. Is there a way to calibrate the S meter Vs SP1 dBm?
Last edited by IZ2245SWL on Thu Jan 01, 1970 12:00 am, edited 0 times in total.
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sdrplay
Posts: 604
Joined: Wed Jan 07, 2015 7:58 am

Re: S-meter Vs dbm

Postby sdrplay » Sat Nov 04, 2017 6:40 am

It is a calibrated system to the input of the RSP. I've just been putting in different power levels and checked the S meter reading and can't see any problem. Can you post an image showing the discrepancy (which RSP are you using?).

I've put in -73dBm at HF and the S-Meter reports S9 and I've also put in -93dBm at VHF and the S-Meter still reports S9 - which is correct as per the Region 1 specification.

Best regards,

SDRplay Support

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IZ2245SWL
Posts: 6
Joined: Wed Dec 21, 2016 7:09 pm

Re: S-meter Vs dbm

Postby IZ2245SWL » Sat Nov 04, 2017 5:01 pm

First of all I want to higlight my total satisfacion for the SDRPlay. It is a true little great receiver.
I work mainly in HF with a passive resonant home made magnetic loop placed in my balcony at 2nd floor of 8th.
Despite of so poor conditions I had confirmed QSO from VK, LU (tierra del fuego), Washington state, etc.
For strong signals I see a good match too. The discrepancy is Is for the weak signals.
I attach a hardcopy of SP1 showing a floor noise of -120 dBm (about) and a S3.5.
I'm using a SDRPlay 2 Pro.
Thank you in advance.
Attachments
SP1.jpg
The SP1 hardcopy
SP1.jpg (207.88 KiB) Viewed 181 times
Last edited by IZ2245SWL on Thu Jan 01, 1970 12:00 am, edited 0 times in total.
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Tech_Support
Posts: 225
Joined: Mon Jun 01, 2015 7:00 pm

Re: S-meter Vs dbm

Postby Tech_Support » Sat Nov 04, 2017 6:34 pm

Hello IZ2245SWL,
You power reading is -104 dBm (31 dB below S9) in the LSB bandwidth of your demodulator, which is pretty well spot on. See the reading above the SNR meter in the SP1 display.
The -120 dBm noise floor level is the noise power within the resolution bandwidth of the SP1 display which is only 33.57 Hz. That is why you perceive a discrepancy.

Sincerely

SDRplay Tech_Support

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IZ2245SWL
Posts: 6
Joined: Wed Dec 21, 2016 7:09 pm

Re: S-meter Vs dbm

Postby IZ2245SWL » Mon Nov 06, 2017 5:19 pm

I installed the SDRUNO 1.2 and changing the new RBW funtionlity of SP1 I understood the stuff.
73.

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