Automatic LNA settings w/band

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someYguy
Posts: 128
Joined: Sun Apr 10, 2016 7:12 pm

Automatic LNA settings w/band

Post by someYguy » Wed Feb 28, 2018 7:24 pm

The RSP1A varies its LNA setting (in the device control panel) automatically per frequency band selection. For example, if I have the radio tuned to 10 mhz, LNA set where I want it, and then retune to, say, 100 mhz in the FM broadcast band, the LNA gain automatically increases and raises the noise floor slightly.

I find this annoying because I am constantly readjusting, especially when I use the RSP1a as a spectrum analyzer with SDR#. With the old RSP1 I could leave the LNA off and simply calibrate level by using the IF gain and nothing would change until I changed it again.

Can this behaviour with the RSP1A be stopped? I want the LNA gain to stay where I put it regardless of the center frequency which I select.

Any help appreciated, and thank you :).

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sdrplay
Posts: 978
Joined: Wed Jan 07, 2015 7:58 am

Re: Automatic LNA settings w/band

Post by sdrplay » Wed Feb 28, 2018 7:40 pm

On the RSP1A, the RF Gain reduction range changes from 0-6 below 60 MHz to 0-9 above 60 MHz, the position of the slider looks like it's changing because the range changes. However if you were at setting 3 lower than 60 MHz, you will still be at setting 3 above 60 MHz.

Ideally you should be at 0 (max gain) unless you have ADC overload or inter-modulation issues.

Best regards,

SDRplay Support

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someYguy
Posts: 128
Joined: Sun Apr 10, 2016 7:12 pm

Re: Automatic LNA settings w/band

Post by someYguy » Wed Feb 28, 2018 8:44 pm

Very good and thank you for the super fast response :).

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mark.
Posts: 51
Joined: Tue Oct 03, 2017 9:14 pm

Re: Automatic LNA settings w/band

Post by mark. » Thu Mar 01, 2018 12:38 am

On a related problem. My issue is the IF gain changing, usually going up to full gain, when I switch bands. Multiple times in a listening session I have to manually drag it back down to avoid overload. I do not use AGC.

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g1hbe
Posts: 494
Joined: Sat Jan 17, 2015 3:28 pm
Location: Cheshire, UK

Re: Automatic LNA settings w/band

Post by g1hbe » Thu Mar 01, 2018 12:46 am

Mark - I think this is a known bug. IIRC, it only happens if you have selected 'gain' rather than 'gain reduction'.

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Andy

mark.
Posts: 51
Joined: Tue Oct 03, 2017 9:14 pm

Re: Automatic LNA settings w/band

Post by mark. » Thu Mar 01, 2018 12:48 am

Thanks, I'll switch to gain reduction then.

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