Thank you for your reply, Gilles.
A wiring-problem certainly is worth looking into, especially taking the
course of events into consideration. I shall
give the grounding and other wiring a hard look.
The GPS and Radio antenna are almost as far from each other as possible.
Still, it could perhaps be improved.
Also, I shall try to power the GPS from a surplus battery while it is
mounted in the panel, that would be an
easy test.
Finally, I will talk with my avionics-man about the notch filter.
If, and hopefully-when the cause and remedy is found I shall reveal it
through the forum.
Best regards,
Niels
----- Original Message -----
Sent: Tuesday, July 18, 2006 11:07 AM
> <Gilles.Thesee@ac-grenoble.fr>
>
> Niels Kock a crit :
>> ...
>> It may well be an antenna/screening problem. But why does this problem
>> arise after a some years' impeccable service, and
>> then seem to increase?
>> Can anybody help with an explation which even I might grasp, and a
>> solution?
>>
> Niels,
>
> Please remember that shielding is not a one-size-fits-all solution to
> audio noise problems. It only works for specific cases. Many many times it
> has something to do with proper grounding.
> The appearance after some time may indicate a wiring related issue.
>
> Are all your grounds properly connected at a unique point of the firewall
> ?
> Is your intercom corrrectly wired ?
> Why do you have a long coax run for the radio ? Why not shorten it and (at
> least) gain on the signal attenuation ?
> Are your antennas sufficiently remote from each other ?
> Have you tried running each of the suspected device from a completely
> separate power source (battery), to ascertain the radiated or conducted
> origin of the problem ?
> Since the noise seems to be related to some specific frequency ranges,
> have you considered adding a notch-filter to your radio ? The Garmin
> 400-series call for a check of the VHF entire frequency range and the
> addition of a 1.547 GHz notch filter at the rear of the radio in case of
> interference problem.
>
> Regards,
> Gilles Thesee
> Grenoble, France
> http://contrails.free.fr
>
>
> http://www.matronics.com/Navigator?Europa-List
> http://wiki.matronics.com
>
>
>
--
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