Topband: Topband QRN

[Brad Rehm]

"Is it possible to choke the QRN at the TV power cord? Would a large
ferrite
J core wrapped with as many turns of the power cord be effective in
eliminating or attenuating this signal at its source?
"Steve / VE7SL"

Steve,

It's worth a try.  If the noise is in the lower HF bands and it is
conducted out of the set on the power leads, you'll want to find a
high-permeability ferrite torroid.  One of the 2 1/2" o.d. cores that
Amidon sells should work.  No. 77 material would be good.  No. 33
would be better.  If the problem is in the higher bands--15 to 10
meters--then, a more common No. 43 material core might do the trick.
Seven or eight turns on the core is all it takes.

If I had my choice of solutions, I'd use one of the power line filters
made by Corcom and others.  The trouble with them is that you've got
to intercept the power cord as close to the receiver as possible to
make the really effective.  It's also important to provide a ground
reference for these filters so that they have someplace to dump the
common-mode RF currents they've peeled off of the power leads.

Some of the better filters provide over 50 dB of attenuation of
signals below 30 MHz.  That's much more than you can get by wrapping
the power cord around a torroidial core.  Very few neighbors are
willing to let you install them properly, though.

73,
Brad, KV5V