----- Original Message -----
From: "Fred Fillinger" <n3eu@comcast.net>
Subject: Re: Europa-List: GPS problem
|
| 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.
Cheers,
I agree with Fred. Funnily enough I just read an email about a month
ago where one of us had put his antenna on the starboard footwell ceiling in
the engine room.......... I think he said it worked well, but then there's
agreat big metal thing in there. Might be worth trying.
Does your wayward GPS box accept another antenna, perhaps an active
one? The alternate test is a good one.
Ferg
A064
|