Page 1 of 1

My winndow only goes down to 120 dbm

Posted: Sun Feb 17, 2019 6:07 am
by sdrom33
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

Re: My winndow only goes down to 120 dbm

Posted: Sun Feb 17, 2019 11:10 am
by g1hbe
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.

Re: My winndow only goes down to 120 dbm

Posted: Sun Feb 17, 2019 2:39 pm
by sdrom33
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!

Re: My winndow only goes down to 120 dbm

Posted: Sun Feb 17, 2019 6:40 pm
by ON5HB
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.

Re: My winndow only goes down to 120 dbm

Posted: Sun Feb 17, 2019 6:46 pm
by Roger
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.

Re: My winndow only goes down to 120 dbm

Posted: Sun Feb 17, 2019 7:01 pm
by sdrom33
thanks Roger, this solved it!

Re: My winndow only goes down to 120 dbm

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