[RFI] Common Mode or Powerline Pickup....?

Pete Smith Pete Smith <n4zr@contesting.com>
Mon, 31 May 1999 02:31:53 +0100

I'm lucky enough to have my antennas over 200 feet from the house, so by
and large my RFI problems aren't serious.  In fact, the only time I have
problems with CW is when I'm on 80 meters, full QRO, and with my lazy-vee
array pointing toward the house.  At that point, my wife notices moderate
but annoying cross-hatching on her computer monitor, which I'd like to
cure.  The monitor shows no RFI when I'm on 80 but pointed away from the
house, and on the higher bands antenna direction is unimportant and there's
no RFI.

My working assumption is that this interference is probably not due to
common mode currents on the feedline (CATV hardline coax, mostly on the
ground surface), but rather to signal pickup on the overhead power lines
coming into the house, which are broadside to the antenna.  On that basis,
I've concluded I probably needn't bother with a common mode choke in the
feedline, and should focus instead on power line filtering

Am I correct?  And if so, can someone recommend a good line filter that I
can use for both the computer and the monitor, since there's no way of
knowing how the RFI is getting onto the screen?

Thanks all, in advance.

73, Pete Smith N4ZR

Sometimes a tower is just a tower

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