Asking for a friend

[emt_531]

The California, Kings, particularly Sheriff at 460.600 sounds terrible on my feed. It is a ground level discone DJ-130J, with LMR-400 (overkill) to the scanner. I live in a high residential area with a pre-amp to the scanners. Antenna to scanner is maybe 40 feet. I hear noise and have a ground loop isolator. Ideas and suggestions are appreciated.

 

[KN4EHX]

The California, Kings, particularly Sheriff at 460.600 sounds terrible on my feed. It is a ground level discone DJ-130J, with LMR-400 (overkill) to the scanner. I live in a high residential area with a pre-amp to the scanners. Antenna to scanner is maybe 40 feet. I hear noise and have a ground loop isolator. Ideas and suggestions are appreciated.

Perhaps you are getting noise from something, but I’ve also heard of people having issues when using a pre-amp. You might try using a different antenna without a pre-amp just to see if that cures the problem.

Could also be the officer’s radios. I’m not from there so I can only guess, but depending on the landscape and what type of antennas they are using; if they are running phantom antennas on their mobiles and shorty antennas on their portables that might have a lot to do with the poor audio quality.

In my neck of the woods they use the cheap $12 wire antennas on UHF and can’t seem to understand why their receive and transmit audio sounds terrible. Also tons of hills and valleys in the equation.

Play around with you antenna. Line of sight is still important. Hard to get UHF through a mountain. Keep it simple. If you happen to have a mag mount antenna that would work with your scanner as a test it certainly can’t hurt to give it a try just to see if it changes anything.

 

[tvengr]

What kind of preamp are you using? Cheap preamps can cause all kinds of intermod problems and destroy signals. Try taking the preamp out of the antenna line.

 

[scanmanmi]

With 40' of LMR400 you should be hearing quite a bit. You mention scanners plural, is there more than one? Is it on almost all frequencies? Try shutting as many circuit breakers as you can (or put the rig on a battery) and try to find a noise source. I found a very noisy DVD player that way.

 

[merlin]

Try to get your discone at least above roof line and get rid of the preamp. Even then, you may need some attenuation.
Problem sounds like too hot of signal to the scanner. As mentioned, a poor preamp is worse than no preamp.

 

[vagrant]

Just tested and I am up around Fresno and 460.600 MHz has a very strong signal here whether I'm using my amateur radio with a dual band antenna above the roofline, or my discone also above the roofline connected to an SDR. I use 50' of LMR-400 to my discone as well and it is not overkill, especially for UHF, but I am working to hear signals some distance away so I do not use RG6 with it. I also use a ground loop isolator as I push the audio to a computer and external speaker.

1. Initially it sounded terrible on my SDR because I had it set to AM. Is your scanner set to AM for that frequency?
2. I use an amplifier as well on that discone and I cannot use more than 10 dB of gain as it will raise the noise floor way too much.
3. Could the coax connections be bad? It happens.
4. I would think that even at ground level the discone should receive it fine. Why not test by using a regular scanner rubber ducky antenna instead right at the scanner itself.

I think that transmitter is over on the west side toward San Benito and probably over 3000' ASL. Are you far from the San Benito range? Have you always had this "noise" problem, or is it recent? Anyways, my guess would be the wrong mode, a problem with the coax, or either you or a neighbor introduced something that is causing the noise. Let us know what it was if you figure it out, so it may help someone else one day.