[Elecraft] RFI With KPA500 Full Output on 40m
Vic K2VCO
k2vco.vic at gmail.com
Sun Mar 18 03:08:50 EDT 2012
One or more of the wires going to your system must be resonant on 40 meters and is picking
up RF directly from the antenna.
I had horrible problems when I had an inverted L with the horizontal part over the house.
My alarm is a 'wired' type that has terminating resistors at each of the switches. 1.5 kW
on 160 meters simply vaporized one of the resistors, and heated others at the alarm box. I
fixed it by winding each of the wires going to the switches around ferrite cores at the
alarm box. I also treated the phone line and the wires that go to the battery and the bell
box.
I used various cores, but the square Radio Shack things worked. No. 31 ferrite mix is
recommended.
That fixed it, but I replaced the inverted L with a T and got rid of a lot of RF floating
around.
Since all of your lights are lighting up, I would start with the phone line and the power
supply. Remember, at 40 meters you need to as many turns as you can get around the cores.
Just passing the wire through a bead won't do it.
On 3/17/2012 8:51 PM, 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
>
--
Vic, K2VCO
Fresno CA
http://www.qsl.net/k2vco/
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