Cell Tower Interference / SDR Trunk

[davejl2001]

I have been monitoring a P25 Phase II LSM 700MHZ system for a few years now with a Airspy R2 with no issues. The system is in the range of 769-774 MHZ. Recently a new cell tower was installed very close to my house (1000 feet). I’m now having problems with audio distortion ever since the new tower was turned on. I have played around with the gain with no luck. I’m using the latest version of SDR Trunk 0.6.1 final with my gain set at 15. My power receive level is within the range of 45dB-60dB and the control channel holds sold with no loss. Any recommendations or types of filters would be greatly appreciated. Thanks

 

[KJ4DHF]

There was someone on another forum at 1 time making SAW filters for this problem.

 

[rabbit108]

I have been monitoring a P25 Phase II LSM 700MHZ system for a few years now with a Airspy R2 with no issues. The system is in the range of 769-774 MHZ. Recently a new cell tower was installed very close to my house (1000 feet). I’m now having problems with audio distortion ever since the new tower was turned on. I have played around with the gain with no luck. I’m using the latest version of SDR Trunk 0.6.1 final with my gain set at 15. My power receive level is within the range of 45dB-60dB and the coudesntrol channel holds sold with no loss. Any recommendations or types of filters would be greatly appreciated. Thanks

You will need to specify the frequency range and type for a custom filter. Since you already have an R2, I suggest you download a copy of SDRSharp v1784 which includes the latest version of Spectrum Spy software.
https://airspy.com/downloads/sdrsharp-x86-dotnet4.zip



This what I get at my location with my R2 and no amp:

 

[davejl2001]

You will need to specify the frequency range and type for a custom filter. Since you already have an R2, I suggest you download a copy of SDRSharp v1784 which includes the latest version of Spectrum Spy software.
https://airspy.com/downloads/sdrsharp-x86-dotnet4.zip

View attachment 175596

This what I get at my location with my R2 and no amp:

View attachment 175597

Already tried something similar to this in SDR Trunk, but still receiving distortion in the 769-774 MHZ range.

 

[rabbit108]

Already tried something similar to this in SDR Trunk with no luck. Still getting distortion

I already tried something similar to this in SDR Trunk, but still getting distortion in the 769-774 MHZ range.

If the distortion is caused by overload from a strong local signal, you must determine the frequency of that signal to order a custom filter. If the distortion is not caused by overload, then you have a problem with SDR Trunk.

If you right click on the scan in Spectrum Spy, a yellow line will collect peaks from intermittent signals. The longer you let the scanner run, the more peaks you will collect.



If you are not able to run a Spectrum Spy scan, I am not able to help you any further. I don't do trunking.

 

[maus92]

LTE / cellular interference will be wideband aka 5-10 MHz per channel just below the talk-out frequencies for the 700 MHz public safety band (Band 14). Ironically it's FirstNet. A filter would need to block below 769 MHz as it is not a specific frequency. There is a band of uplink frequencies just above 775 MHz, but that would come from subscribers aka low power and unlikely to affect you.

 

[WB5UOM]

Might be interesting to see what it looks like if you zoomed in on the 769-774 area you mentioned

 

[davejl2001]

Here it is.

 

[WB5UOM]

Is any of that what you are trying to monitor?

 

[davejl2001]

Yes.

 

[wtp]

you might have to move.
one thing i used to do when going near a tower here is to point the antenna at the tower.
that is the null point for antennas.
best reception is on the broad side.
we now try to avoid going down the road and tower.

 

[maus92]

IDK, lots of usable signals in the slice of spectrum.

 

[WB5UOM]

Thats what I was kinda thinking, op have you tried a different software?
maybe. just a thought

 

[davejl2001]

IDK, lots of usable signals in the slice of spectrum.

When I increase the gain, the distortion gets worse.

 

[maus92]

When I increase the gain, the distortion gets worse.

Which makes sense. But as I said, lots of usable signals in that waterfall shot that should not require boosting gain, but you'll have to be specific about what system/frequencies you are having trouble receiving.