[RFI] RF into home alarm system

W5GN w5gn at mxg.com
Sun Oct 18 22:19:05 EDT 2015

My first time on the air from our vacation cottage in Ireland,
my 100 watt IC756PROIII hit our alarm system; my polywire
inverted V was only 14 feet high and the 80 meter leg passed
near the equipment.

I disconnected the phone line and ran 8 turns around a 2.4 inch
toroid and the problem went away, so I operated in the 2006
WPX SSB contest with no problems in my house, and hopefully
didn't impact our one nearby neighbor.

So I was dismayed on Monday when my cousin stopped by and said
"I saw yer neighbor Michel at church on Sunday; he said he
heard you on the radio this weekend"

Crap, I think, and asked Mihal, "Do you know how he heard me?
Was it the TV, or the radio, or the stero, or the phone?"

Naw, Barry, he heard you thru the window as he walked by.


Barry, W5GN

-----Original Message-----
From: RFI [mailto:rfi-bounces at contesting.com] On Behalf Of W5JR Mike
Sent: Sunday, October 18, 2015 8:35 PM
To: rfi at contesting.com
Subject: [RFI] RF into home alarm system

As the subject line says. 

For the past two years, I've not caused any issue to our home alarm system.
The typical 4 wire JK style wire run all over the house. Lots of doors and
windows. And 13 smoke detectors. I run 1.5 kw, 160 to 10 (less on 30m) and
nary a peep. 

Last eve, wanting to play a bit in the Pre-Stew on 160m, but as yet not
having my 160 antenna repaired, I was able to get the tuner to find a match
on the 80m OCF. Even with just 100w, folks were answering my CQ's. I'm sure
there was lots of stray RF floating around. 

My wife came rushing over to the shack in a panic. It turned out the alarm
was in full on,  every annunciator sounding simultaneously. Fire, intrusion
- one big mess. I knew there wasn't a fire as the control panel told me
there was a fault condition. Nothing on the control panel would clear it.
Only by removing all power was I able to cleared it. 

Now that I've prepped you with the setup, the question is if anyone has had
to tame their alarm system to reduce its RF susceptibility and what steps
did you do to get there?

I don't expect the installer to have any useful input, nor the manufacturer,
but they may have dealt with this for a neighbor to a ham. 

I'm anticipating the recommended solution will be lots of Mix 31. Can I wind
all or several of the wires together on donuts? Am I better off using  one
on each wire (yes, still multiple turns)? Would adding bypass caps be of any

Mike / W5JR
Alpharetta GA
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