UHF Interference
Submitted: Sunday, Oct 05, 2003 at 20:52
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Radar
Hi All,
I am having a little problem with my UHF. Whenever I put my lights on to high beam there is an interference niose.
Does anyone have any ideas??
Thanks in advance.
Radar.
Reply By: chrisfrd - Monday, Oct 06, 2003 at 21:58
Monday, Oct 06, 2003 at 21:58
Hang on! MORE INFO please!
Firstly, what is the truck? How old is it? How old is the battery? What condition are the electrical systems in?
I'm presuming that you have the engine running when the high-beam lamps are on. Am I correct?
If the engine is running. then the interference that you are getting is probably from the alternator and the associated rectification systems that you have. Modern rectifiers are built into the alternator housing, whilst older trucks have the rectifiers as a separate system, bolted onto the firewall, (the old 40's and 60's were like that by memory, but I have only ever worked on Patrol's and newer Cruisers.
If you are having noise problems only when the engine is running, then your rectifier, (regulator or such) are faulty or at fairly high load levels. Some older regs clicked and buzzed so much it was like listening to a chain-saw! If this is the case then there are a few things, (short of renewing them), that you can do to sort it out. Firstly, on older Petrol trucks, have the ballast resistor checked and renewed if suspect. Secondly,
check the capacitor on the distributor checked and renewed. Then, move to the alternator and the regulator.
If this doesn't sink it, then you could be getting RF based interference from somewhere in the car. This is uncommon on UHF though, as the FM operation of the radio lends itself to better noise suppression.
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