Ian M wrote:
> my skymap aerial is in the same place, with no problems. The antenna
> can see through the panel & the glazing & body with no attenuation.
> GPS can be affected by VHF radio nearby, so try with & without the
> radio switched on. If it is the radio, you need an in-line notch
filter
> (Garmin do them, maybe via AFE at Oxford?).
>
I can't see how a notch filter will solve the OP's problem, as this
item is to trap harmonics while transmitting and only needed on
certain oddball (in U.S.at least ) frequencies at that. As Nigel has
pointed out, interference from a noise source in the panel is a likely
suspect, but this type of noise weakens with the cube of the distance
---From the source, so it needn't necessarily be moved much. If it
occurs when a comm is merely turned on, and it has a switching
regulator, that's a robust noise source. I'd first try moving the
antenna temporarily to various other places in the panel, even in the
area of the right-side shelf. Moving it to the top of the fuselage
will mean quite a few more feet of coax, for up to maybe 40% loss in
signal strength, so that even a compromised location somewhere in the
panel, like inside but underneath the shelf, can be acceptable.
Reg,
Fred F.
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