My winndow only goes down to 120 dbm

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sdrom33
Posts: 128
Joined: Sun Dec 09, 2018 4:38 pm

My winndow only goes down to 120 dbm

Post by sdrom33 » Sun Feb 17, 2019 6:07 am

My rsp1a before had a signal window going down to - 140 dbm. Now it is two days it goes down to - 120 dbm but the rsp seem to wodk normally, not broken. Any help please

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

Re: My winndow only goes down to 120 dbm

Post by g1hbe » Sun Feb 17, 2019 11:10 am

Hello. The displayed noise level will depend on the sample rate/bandwidth you have selected. Try selecting a narrow bw (maybe 2MHz sample rate with 8 decimation) and then a wider one (try 2 MHz with 1 decimation) and you will see the difference.

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Andy

sdrom33
Posts: 128
Joined: Sun Dec 09, 2018 4:38 pm

Re: My winndow only goes down to 120 dbm

Post by sdrom33 » Sun Feb 17, 2019 2:39 pm

Thanks Andy, but my problem is that the bottom of the scale before started at 140 / 145 dbm, now it has gone begins at 120. excuse my english hope you understand!

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ON5HB
Posts: 140
Joined: Sat Dec 29, 2018 1:07 pm

Re: My winndow only goes down to 120 dbm

Post by ON5HB » Sun Feb 17, 2019 6:40 pm

In fact it's quite simple.

The ADC can do 12/14 bits at low bandwidth, this means a high dynamic range.
If you use a wide bandwidth the number of bits go down to 8 bits, as such the dynamic range drops.

12/14bits can do about 140dbm of range where 8bits does about 90dbm. (not exact figures just to explain it)

So if you make the reception range wider, the number of bits drop and the S/N ratio gets worse.

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Roger
Posts: 217
Joined: Fri Dec 29, 2017 7:59 pm

Re: My winndow only goes down to 120 dbm

Post by Roger » Sun Feb 17, 2019 6:46 pm

sdrom33 wrote:Thanks Andy, but my problem is that the bottom of the scale before started at 140 / 145 dbm, now it has gone begins at 120. excuse my english hope you understand!
If you mean the scale at the left hand side you can change it in the SETTings for that window as shown below. if this does not answer your question post a screenshot showing the problem.
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sdrom33
Posts: 128
Joined: Sun Dec 09, 2018 4:38 pm

Re: My winndow only goes down to 120 dbm

Post by sdrom33 » Sun Feb 17, 2019 7:01 pm

thanks Roger, this solved it!

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

Re: My winndow only goes down to 120 dbm

Post by mark. » Tue Feb 19, 2019 2:37 am

This is why I have posted a few times over the last year that I think it would be handy to have that settings window open and close with the rest of them instead of always having to click it on and drag it into place. I use those sliders a lot. But I never get a reply so I think I must be the only person that would like that feature.

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