Hi, Jon (& the list) --
This summer we had a new baseboard heating system installed, along with a new
but low-tech bottled gas-fired furnace. When heating season arrived this fall,
I quickly learned that my CW on 80 meters was keying the furnace on and off!
The control board for the furnace is not particularly sophisticated, but it
*does* contain a lot of relay-control logic for turning on the circulators for
the different zones and for various fail-safe requirements. The long run to
one of my zone thermostats at a far away place in the house was picking up the
RF and bringing it to the relay control board, where the anti-spike diodes
across the relay coils on the control board were rectifying it.
I tried ferrites on the thermostat wires first, for a quick fix, but that
didn't work. Instead, I found it necessary to add a pair of Radio Shack 100
microHenry RF chokes (RS # 273-102C) in series with the offending thermostat
wires at the barrier strip inside the control box and then bypass each of them
to the controller board ground with (say) a 0.001 microfarad capacitor.
Thus far only one thermostat link has caused the problem but I fully expect
ultimately to have to add two chokes and two capacitors for each zone as I find
time to operate on all the other HF bands!!!
73 -- Bud, K2KIR
At 09:30 AM 2000-11-20 -0600, you wrote:
>While operating 40 meters last night during SSB Sweepstakes, I ended up
>working my furnace! Around midnight my wife came into the shack and said
>that whatever I was doing sounded like someone banging on the ductwork. She
>couldn't sleep. Our nephews were spending the night and they complained
>Today I had her listen and she confirmed that whatever it was was coming
>from the furnace.
>What the heck would be inside a furnace that would be affected by RFI? It's
>an old, old furnace (probably original - 20 years or so). So it isn't real
>electronic or anything. Could dirt or dust be affected?
>NA9D (ex: KE9NA)
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