[RFI] can a tower re-radiate RFI?

David Robbins k1ttt at verizon.net
Mon Jan 25 08:14:08 EST 2016

DANGER WILL ROBINSON!!!  that could be a very dangerous situation... get a qualified electrician and the power company there ASAP and get everything checked out.  I had a neighbor who went through that and it was the ground at the transformer going to their meter that was bad, they blew all sorts of stuff, replaced it, and blew it up again before it was found.  don't trust a single voltage reading on a circuit to be correct either, as long as the loads are approximately equal voltages can look ok, then have one motor start, even a refrigerator, and it can swing the voltage on both circuits all over the place.  at another place where I saw this when certain loads were energized their circuit would go down to 75-80v and the other side would go up to 160v, not good for lots of stuff on either circuit!

and yes, this can make the neutral be not so neutral, your tower may be the return path for substantial current if this happens under certain circumstances, DO NOT disconnect or connect anything that goes to the tower, you may find that a simple coax is taking the unbalanced current to ground that way and disconnecting it could result in high voltages between the coax and radio while you are holding it!

Jan 25, 2016 07:59:59 AM, kzerocx at rap.midco.net wrote:

“I?m not certain the AC in my house is up to specs.......I have a couple of branch circuits constantly blowing incandescent bulbs, not sure why, last year our prelit Christmas tree (on one of those circuits) blew every bulb, one string at a time....WW3S"

It sounds like you have a missing, or poor, neutral connection. If you measure the problem branch circuits, is the voltage high?

I was also about to suggest disconnecting EVERY conductor to the tower to see if the RFI abates. You may have something connected from the house to the tower that is energized all the time, such as neutral current, mentioned in the previous sentence, flowing on a coax shield.

A tower will re-radiate RFI. Years ago, a friend had terrible broadcast band mixes all over 160 and 80 meters. I DFed the mixes with a broadcast field intensity meter...a Potomac Instruments FIM-41. Everything was coming from my friend’s tower. It turns out that he had an old run of Heliax going up to a remote coax switch about 50 feet above ground level. The Heliax was unjacketed. The poor contact between the tarnished copper outer conductor wrap-locked to the galvanized zinc coating on the Rohn 25 was behaving like a large number of detector diodes. Once the Heliax was replaced with jacketed cable, the mixes were gone.

k - zero - cx
Rapid City, SD 
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