Computer Interference

[ScannerDude244]

Morning everyone! Today I took out my computer to get dusted out and I notice once I powered it down I was pulling in some frequencies I never got before. And soon as I power the pc back on they disappear. Should I get a band pass filter or is there ways to kick the interference without one?

 

[ka3jjz]

You're going to need to do some detective work to determine what in the PC is actually causing the issue. It could be the power supply, the display, a crappy mouse or keyboard - Try turning things on/off or unplugging them to see what is actually causing the issue. Once you have isolated the cause, then folks can suggest some way to mitigate the issue. Personally I doubt you will ever get rid of it all, but one can hope...

Some general rules here - if you have lots of cables laying about in and near the PC, wrap them up into a loop and tie off with wire ties. This includes keyboard cables, (if possible) mouse cables, modem cables of any kind, all of it. Sometimes putting the power supply on a heavy duty filter will also help (won't hurt, for sure). Any antennas near the PC should run at right angles, and away from it - never in parallel. Keep them as far away from the PC as possible

73 Mike

 

[benbenrf]

You want to try a couple things:

1) Power the scanner off an independent 12vDc battery source (the idea is to isolate the scanner from the same a.c. power and phase circuit as the PC). Alternatively, iff you have a PC UPS, run the PC from the UPS - with the UPS disconnected from the wall AC socket.

Now switch the PC on - has the interference gone? Yes/No.

If yes then the noise stemmed from sharing the same AC circuit, and you are going to have to use a filter in the ac circuit at some point, but if not, try this: purchase a role of tin foil and wrap the PC well in a couple layers of tin foil, ensuring no gaps are left open at any point. Now switch the PC on.

Interference should now be gone, or at least substantialy reduced - you may try also wrapping the power cord from plug socket to PC as well, but I doubt you'll realise much in the way of noise/interference reduction. Interference reduction is going to come from wrapping the PC and/or isolating it from the same power source as the scanner.

The question now of course is, just what component in the PC is causing the interference - and it will almost certainly be the power supply as has already been suggested: poor screening, or a poorly laid out ground circuit. You can open up the p/supply and solder in a whole bunch of earth lines, all running to the same point - but quite frankly, it'll be easier to throw it out and replace it with a decent one, or replace the box/tower that the parts are contained in.

 

[ScannerDude244]

1) Power the scanner off an independent 12vDc battery source (the idea is to isolate the scanner from the same a.c. power and phase circuit as the PC). Alternatively, iff you have a PC UPS, run the PC from the UPS - with the UPS disconnected from the wall AC socket.

Now switch the PC on - has the interference gone? Yes/No.

You read my mind! After doing some detective work like ka3jjz, the first thing I did was unplug the ethernet cable I did have interference with MY DSL modem awhile back till I moved it over to the next room. So I unplug it nothing, So I went down the list nothing. So I can say it has to be the PS I hope! Benbenrf I do have the PC and radios plug into the same UPS. Also should I move one of the UPS over to the next outlet? Or it wont make a difference? So after I'm done with my coffee time to move wires around and see what happens.

 

[benbenrf]

What !! - are you now telling us that your PC (and radio) are normally powered off the main domestic AC circuit in the house through seperate UPS's?

UPS's contain invertor circuits - they take DC voltage/current and turn it into AC voltage/current when the mains circuit is down, and to do that they need to generate frequency (50Hz - 60Hz),. They are frequency generators and can be the cause of all sorts of noise/interference if not designed with care.

Add to the list of things to eliminate - UPS x 2! i.e. run the same tests with/without the UPS's

Will plugging one of the UPS's into another outlet have any effect?

Theres' a couple of answers here:

No if the AC circuit that feeds all the outlets is the same circuit, and is switched on.

Yes if the circuit AC power is switched off and the batteries in each UPS are been used to power the inverter circuits to supply power to the PC and radio respectively (assuming it is the AC circuits in the house that are delivering the interference).

Yes if the interference is down to physical distance i.e by plugging into a distant outlet you increase the physical distance between the PC and the radio.

You could run the tests with certain other household goodies disconnected e.g. that old fridge/freeze in the shed, the gold fish's airpump, that flcikering neon ballast in the garage ........ it could be one of a 101 things you may land up having to go through ultimately.

Keep us posted and good luck!

 

[ScannerDude244]

Just one UPS it is old and doesn't do good with my 1k power supply high end gaming rig only last like 4 minutes lol. But I did take it out and hooked up some apc power strips one just for the radios and one PC and I did notice less interference. I do have the electroline multicoupler power adapter hooked up on the same strip as the radios should I move it over it to the PC strip?

 

[benbenrf]

Tell you what Scannerdude244 - can you make a 20sec - 30sec recording of the interference you are suffering from? Record it as a WAV file if possible (not MPEG if that can be avoided) and email it to me - attached as a WAV file idealy, but if it has to be MPEG, then fine.

I'll run it through an analyser this end and lets see what results we get.

 

[ScannerDude244]

I know this thread is old, but I'm still having the same problem I tried all of above with no out come. Anyone have more suggestion?