[Elecraft] Slighty off topic - 80 meter second harmnic how to stop

[Mark Goldberg]

I would expect that if it was getting into an alarm system, the alarm would
fail in some way. I had a bad problem with mine, cured by a 5th order 200
kHz lowpass filter where simple ferrites and caps did not work. The alarm
system has low frequency digital data. I built it with some caps and a few
turns on mix 31 cores I had. Since it is not a 50 ohm system, the filter is
not exactly as designed, but it worked well enough to completely eliminate
the problem. I put it at the alarm controller that was getting affected.

73,

Mark
W7MLG
On Feb 23, 2016 2:04 PM, "paulb" <xtr348165 at xtra.co.nz> wrote:

>
> Hello again folks
>
> Thanks to all for the suggestions and hints to  what this problem could be.
>
> Tests have been done at 2 locations; my own home station and here at
> another
> property  ( work in progress as we
> politely say..) about 125km south of Auckland.
>
> The same second harmonic garbage is heard at both places. Over the last day
> I have completely swapped out
> all the 80m and 40m antenna and feeder components here in the provinces. No
> change.
>
> What I now strongly suspect is the only common point at both locales;
>
> both properties have burglar alarms installed.  Both are almost identical
> well known European name brand units.
> There is no detectable RF radiation from the processors or wiring.
> The clincher now that I think about the last time we ran 2 stations here
> without any drama
> was before the alarm was commissioned here.
>
> I have dropped the supply and backup DC to the alarm here without any
> change,
> Likely 3.5 meg RF is simply hammering the PIR's, cable runs are in the roof
> cavity.
> Can't %100 prove this without fairly major re-wiring, will leave it as is
> for the meantime,
>
> thanks again guys
>
> cheers from ZL
>
> Paul
> zl1ajy
>
>
>
>
>
>
> --
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