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[RFI] WAF - Worked all furnaces!

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Subject: [RFI] WAF - Worked all furnaces!
From: Bud Hippisley <k2kir@telenet.net> (Bud Hippisley)
Date: Mon, 20 Nov 2000 10:58:21 -0500
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!!!

Good luck.

73 -- Bud, K2KIR

At 09:30 AM 2000-11-20 -0600, you wrote:

>Hi all,
>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?
>Any ideas?
>Jon Ogden
>NA9D (ex: KE9NA)

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