High noise floor on RSP2??

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N8YYB
Posts: 2
Joined: Thu Dec 22, 2016 11:49 pm

High noise floor on RSP2??

Postby N8YYB » Fri Dec 23, 2016 12:00 am

I am new to the whole SDR thing. Used to be an active ham and left the hobby for a while. I just dove in with the RSP2. I tried using the Boni-whip but the noise and effectiveness did not impress me so I purchased the ML-200 with high hopes. Again, the noise floor on the SDR is around -70dB and I did just as well or better with one of those BNC connected accessory wires that come with many SW radios. I actually emailed Dennis at Bonito. He saw the screen shots and pointed out that high noise level. He said that I may have an issue with the RSP. Me having not ever used one before or know anyone else with one, I have no point of reference on what to expect. I just tried the RSP outdoors with that wire and could not even pick up local AM radio very well. I'm concerned and have no way of knowing short of ordering another one and comparing them. Any suggestions or help is appreciated.
Last edited by N8YYB on Thu Jan 01, 1970 12:00 am, edited 0 times in total.
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N7RJN
Posts: 4
Joined: Thu Dec 22, 2016 12:07 am

Re: High noise floor on RSP2??

Postby N7RJN » Fri Dec 23, 2016 4:02 am

Do you have a screen shot showing the noise floor?
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DK7OB
Posts: 47
Joined: Thu Mar 24, 2016 7:14 am

Re: High noise floor on RSP2??

Postby DK7OB » Fri Dec 23, 2016 8:22 am

Did you try to reduce the gain on the RSP?

The RSP has a limited dynamic range and can be easily overdriven with a good broadband antenna if gain is set too high. In this case the noise floor increases dramatically.

How to reduce the gain depends on the SDR software you are using. I am running gqrx on Linux.

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g1hbe
Posts: 195
Joined: Sat Jan 17, 2015 3:28 pm
Location: Cheshire

Re: High noise floor on RSP2??

Postby g1hbe » Fri Dec 23, 2016 9:51 am

Is the noise level high with or without the antenna connected?
Is this on input A, B or Hi-z?
Which software are you using. HDSDR and SDR# do not read absolute values (or they didn't last time I used them). SDRUno gives a real -dBm reading.

Here is what my RSP2 shows:
Ant: Hi-z, but no antenna connected.
SR: 2 MHz, Dec 2
AGC: Medium.
Frequency: 1.5 MHz.
Mode: AM
Filter BW: 8 KHz
Indicated noise level: -130dBm
When loop antenna connected, noise rises to -120dBm.

If you have a low noise level without antenna and it goes very high when you connect one, you either have a very high local noise level or the RSP is overloading.
Note SDRUno currently has a bug in the gain control. When changing modes, band or SR's, the gain may be set very low and the displayed noise level will look high and there may be a large centre spike. Just click on the gain slider to correct this. UPDATE: Version 1.12 of SDR Uno fixes this bug, so check you have the latest version installed.
I doubt your RSP is faulty.

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Andy

N8YYB
Posts: 2
Joined: Thu Dec 22, 2016 11:49 pm

Re: High noise floor on RSP2??

Postby N8YYB » Fri Dec 23, 2016 2:27 pm

Thanks a bunch for the quick replies! I disconnected all antennas and basically the noise floor on all inputs and bands shower between -112 and -116db which seems acceptable based on what y'all say. I did the software upgrade to 1.12 and that seemed to help a bit. Again, right now I am without the real antenna as I am waiting for the ML-052 to arrive. I do have an attic mounted disc-cone antenna for VHF/UHF and that noise level has also dropped a bit. I will keep an eye on the situation. There are just too many variables to deal with so my brain's ADC was a little overloaded as well! Happy Holidays and Merry Christmas.
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DanubeBCL
Posts: 159
Joined: Sat Jul 02, 2016 12:39 pm

Re: High noise floor on RSP2??

Postby DanubeBCL » Fri Dec 23, 2016 5:14 pm

If I understood it right the noise level rises when any kind of antenna is connected: Bonito MiniWhip or simple random wire.
Then I should say the noise level in and around your house is high.
a) Are the antennas far away enough from PCs and monitors?
b) Does the receiver have a good ground connection?
c) Have you got some common mode choke (current balun) at hand which you could insert between coaxial cable and antenna input?
d) Can you check with another receiver?
Any countermeasures are of course useless when your neighbours or your own house generate lots of RF noise. Unfortunately normality with modern consumer electronics.
73, Heinrich

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