Topband: Tracking noise

[Donald Chester]

I have found one of the most effective tools for tracking down line noise 
and electric fence QRM is a little hand-held portable radio from Radio 
Shack.  It has the AM broadcast band, FM and "aircraft".  The aircraft band 
is just above the FM BC band, but uses AM.  The whip antenna can be 
retracted to reduce sensitivity as the noise source is approached.  I have  
been able to locate noise sources to the exact pole using one of these 
things.  A AM broadcast receiver is all but useless because at those 
frequencies the noise may travel along the lines for miles.  Of course, you 
want to avoid an aircraft receiver that features a built in noise blanker 
that cannot be turned off.

A general coverage receiver  works better still.   One can get a  general 
location of the noise starting at the lower frequencies, and keep tuning 
higher until the noise is almost gone.  Then travel up and down the line 
till the noise reappears, follow it to the strongest point, then keep 
repeating the process.  By the time you get to 10m, you should be pretty 
close to the source,  The VHF aircraft band radio can be used to pinpoint it 
exactly.

One major problem I have lately is that EVERY vehicle we now own puts out so 
much ignition garbage that it obliterates all but the  strongest line noise 
on the portable radio.  The required travelling distances are useally too 
great to walk, and it is unsafe  to attempt to ride a bike along our  local 
highway because of idiot drivers.  Evidently the problemt with the cars is 
electronic ignition, since noise tracking was less a  problem in older 
vehicles that used mechanical ignition points.

Don K4KYV

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