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This category was created to discuss various questions and topics regarding ExpertSDR2 operation.

ТЕМА: S-meter reading not lower than S3

S-meter reading not lower than S3 26 Май 2021 15:13 #1

  • pa3hfn
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Hello,

I bought a sunsdr2 dx a few weeks ago.
Everything works fine.
The only thing that strikes me is that the s-meter does not go lower than S3 without antenna.


Exchange the Pc, swapping analoge power supply, connection the eath or disconnect. Notting helps.
There is always min. S3 (noise) on the meter without any antenna.

What do i wrong?

Berto
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S-meter reading not lower than S3 29 Май 2021 17:05 #2

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Hi Berto,

The EESDR S-meter is measuring the power within the RX passband instead of monitoring AGC voltage like most legacy rigs.
If you disconnect your antenna and vary the bandwidth, you'll notice the s-meter reading will be less as you decrease the bandwidth.

Flex and other SDRs behave the same.

Hope that helps,
Bob, W8FB
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S-meter reading not lower than S3 01 Июнь 2021 07:45 #3

  • Rome
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Hi, all.
Please refer to the FAQ page, ESDR2 section, Q#6.
eesdr.com/en/faq-en
Роман, Roman
Expert Electronics
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S-meter reading not lower than S3 01 Июнь 2021 10:45 #4

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Berto

as others said , you are not doing anything wrong

This is how things are measured on true Direct sampling rigs

the S meter will always show some signal as measurements are made at the ADC input and referred back to the antenna by dividing the power at the ADC input by the total gain. So as well as measuring noise from the antenna, you are also measuring the noise generating within the receiver. Even with no antenna it will be measuring noise-( all electronics will have some Nosie) FFT bins

But do not panic as the S meter is calibrated and is very accurate

Also while on this subject since sounds like possibly first experience with a true SDR:

Changing Pre- amp or Attenuation - will not effect the s-Meter readings they will always be calculated at the input so the s meter will not change value like many traditional radios when you use attenuation or turn on a pre- amp.

that said a S9 singal is a S-9 signal regardless of Pre-amp or attenation being applied.
Please do not email me and ask for help I no longer will be part of this, If I could delete /remove my profile I would do so.
Последнее редактирование: 01 Июнь 2021 10:46 от N8SDR.
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S-meter reading not lower than S3 02 Июнь 2021 20:01 #5

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Hello,

Thanks for the info.
I found the setting in 'Options' -> 'Use wide RX filter' + 'Auto enable'.

If i now pull the antenna plug, then the overall noise level drops to -135 (under S1 at the meter).
So the bandfilters switched on and the total signal level on the ADC drops. Do i understand that correct?


wide_rx_filter.png


(I am very happy with the SunSDR2 dx :-)

Regards,
Berto
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