[Elecraft] RFI With KPA500 Full Output on 40m

[Mike K2MK]

Hi Jim,

I think it may be a fact of life with alarm systems since they have wiring
all over the house. On mine, high power would signal an alarm identified as
a fire alarm. I identified the wires in the alarm panel that went to the
smoke detector input screw terminals and added a clamp-on ferrite core.
Problem solved. 

In your case you should identify the cables (probably 4 or 5 conductor)
coming from the alarm keypads and clamp on a core on each one.

Anybody with an amplifier should probably have a supply of clamp on ferrite
cores. Odd things start to happen as you approach legal limit. My heated
matress pad would start blinking also on 40 meters. I had to use a larger
diameter split core and wrap the AC power cord for the matress pad
controller through it several times to solve that one.

73,
Mike K2MK


Jim Bennett wrote
> 
> Just when one thinks all is good in the world... I re-worked a Hustler
> 5BTV so that it covers 40-30-20-15-10 meters, rather than 80-40-20-15-10.
> The mod was simple - cutting off five inches from the top tube. No
> problem. It now has a 1.1:1 SWR across most of the bottom of 40 meters.
> Sweet. Kinda.
> 
> When I crank my KPA500 up to full output on 40 meters, I get RFI on my
> home security system. Lights up all the remote panel lights and beeps.
> Luckily it does NOT set off the alarm. If I back off output to 350 watts
> or so, no RFI problem. Both ends of my RG-8 coax have ferrite chokes. This
> problem ONLY happens on 40 meters; full power on any of the other bands
> causes no issues. 
> 
> The vertical is mounted on the ground, 25 feet away from the house, with
> about 40 fairly short radials. The security system controller (an Ademco
> 4150, 21 years old) is in a metal case, and is located in a closet on the
> second floor of the house.
> 
> Anyone else have RFI problems with their security system? If so, how were
> you able to cure it? I was thinking that perhaps ferrite beads on every
> lead coming into the controller box may do it?
> 
> Tnx, Jim / W6JHB
> Folsom CA
> 


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