In the May 2012 edition of QST,
"Hands-On Radio" column author H. Ward Silver has an
article titled, "RFI Hunt." It is a very interesting saga
of discovering, then troubleshooting, then correcting a
very strange and unlikely issue. In a nutshell, Mr. Silver
installed a new 105-foot dipole antenna about 30 feet over
his house and, unbelievably, when he operated CW at 30 or
40 meters (at 25 W or higher), the door safety latch on
his self-cleaning oven would energize during the dot or
dash transmission. He works his way through many
iterations of line chokes, bypass capacitors, and
shielding within the oven to finally stop the
interference. His assumption throughout the process was
that RF energy was being coupled into the oven electronic
controller and triggering the solenoid driver circuit.
The illustration he provided implies that his "shack"
is in the next room. Since with a good match the ladder
line emits very little radiation, and the dipole is so far
above the house, is just seems unlikely to me that the
problem is RF induction. Maybe it really is.
wonder whether the problem instead is a spike of just the
right characteristic being sent on the AC house wiring. No
doubt he has a very good ground bonding system so the
signal would have to be conducted on the neutral or even
the hot wire each time the transmitter is keyed. The
kitchen wiring, per modern electrical code, would not
share an AC circuit with another room, but it is possible
that the two Romex cables run parallel to each other in
the wall or ceiling. If the house is older, and/or
rewiring has been done, it's anyone's guess how the wiring
One sure test would be to place a dummy
load at the transmitter and see if the problem persists.
If so, then RF coupling would be entirely ruled out, and a
simpler solution might be to plug the radio into a
different circuit. Having read Mr. Silver's column for
many years, I know he is a very smart guy and therefore
might have already taken that step, but even smart guys
occasionally forget something. What say ye?
cannot provide a link to the story because only ARRL
members have access to the electronic version, and
otherwise you would have a hard copy to refer to.
- Kirt Blattenberger
Progenitor & Webmaster