Can Someone Help with A Interference Issue?

[ncsflorida]

I've got this strange issue, well maybe not so strange to hardcore scanners, but to me it's got me puzzled.

I know what's causing it but the static is really bad. This happens only when I've got my main cpu on. But it doesn't happen every single time, only some times.

I've uploaded an audio piece of the static, as you can tell the actual audio is barely audible.

scanner-static.mp3


Anyone have an idea what component it could be or something I could buy to help with situation? I've got a ground loop isolator on the audio line that goes into the pc from the scanner.

Thanks.

 

[w2xq]

After listening to the file, I don't know. If you unplug the scanner's audio cable and/or move the scanner away from the PC, does the interference level change? If the scanner also runs on batteries, does the noise change if you unplug the wallwart?

 

[W2NJS]

All computers radiate RF energy at low levels and there's not much that can be done about it except to move the receiver away from the computer. My Dell desktop has a particularly strong birdie on 146.52 mHz, of all places.

 

[kb2vxa]

No doubt in my mind it's impulse noise, not like any computer or wall wart hash I've ever heard. Since it comes at random intervals having the "cpu" on likely is coincidental with what appears to be power line leakage. Sounds like you have a bad insulator or damaged equipment on a pole in your area, maybe a tree branch in contact with a line. Further investigation is needed like walking the neighborhood with a VHF portable in AM mode on an unused frequency.

Sorry to disagree with you guys, it appears you have been misled by the mention of the "cpu".

 

[ncsflorida]

Unfortunately moving the pc and/or scanner is not possible at this time.

The interference happens on 155.130 frequency, other frequencies have a strong signal. I know it's the computer but I'm not sure what causes it on that frequency only.

The computer is on a surge protector but the scanner isn't.

Antenna is ST2 if that helps.

 

[radioman2001]

Try some toroid coils on both the power cable to the computer and the audio line from the scanner to the computer. As proof of their ability to removed noise, we have a VHF station that sits on the second floor above a 1 megawatt DTV transmitter, the station appeared to work OK. Field sensitivity testing was interesting, since every time we move a cable or touched the station with our hands the sensitivity would change, then we put a spectrum analyzer on it,and found the noise floor exceeded 2 microvolts. For those of you that can't relate that to a scanner RXer, that's about 1000 times more deaf. Placing toroid coils on all power and antenna cables plus some very steep skirted pass filters brought the noise floor down to reasonable .3 to .4 microvolts. We knew that the noise could not be eliminated all together since our antenna is only 10 ft below the TV antenna.

 

[ncsflorida]

Try some toroid coils on both the power cable to the computer and the audio line from the scanner to the computer.

Not familiar with toroid coils, what are they and how do you install them?

 

[radioman2001]

RS has them, you wrap your wires through them, and they snap shut around the wire.