glcasey
Joined: 01 Jul 2007
Posts: 23
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 Posted: Thu Oct 11, 2007 4:51 am Post subject: 430W installation |
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I have recently upgraded my 430A to a 430W (WAAS capable) in my
Lancair ES. I received the 430 back along with a new slightly larger
antenna. The antenna cable requires a new connector (threaded vs the
old BNC) and the "book" from Garmin recommends a length between 13
and 35 feet to get the recommend 3 to 7 db loss. Whether they
"require" at least a 3 db loss is not 100% clear in the manual.
Anyway, I installed the antenna under the glare shield in the same
place as the previous antenna, adjacent to the Pinpoint(now Chelton)
GPS antenna. Originally the Chelton used a Crossbow GPS receiver
that was a little marginal and it dropped out now and then, while the
Garmin was "bullet-proof" and often received an adequate signal when
inside the steel hangar (door open). The Pinpoint GPS has been much
better and hasn't dropped once since I installed it. It has a larger
antenna than the previous postage-stamp version, but didn't seem to
interfer with the Garmin reception. Now things are different and the
Garmin is having trouble. First thing I did was change my 2-foot
antenna RG400 to a 13-foot RG400, but there was no detectable
change. I raised the antenna as high as possible while staying under
the glare shield. Then I mounted it to a small aluminum ground plane
and laid it on top of the radio stack, simulating a mounting on top
of the glare shield. The height of the signal bars seems to be
independent of all those changes, including the cable length. It
does receive lots of satellites, typically 9 usable signals at any
given time, so what could possibly go wrong? Every once in a while
the GPS will drop out completely - not just giving and integrity
warning, but a complete loss. When I look at the signal strength
page I will see perhaps one hollow bar and nothing else. How could
it lose all the satellites at once? After maybe 30 seconds to 3
minutes it comes back on line and works well again, including the
vertical navigation functions. I can't come up with a common event
that triggers this - it's not a com transmission, but it seems to
happen after 10 minutes or so of flying and I haven't yet had it
happen twice in one flight, although all my flights have been short
since the installation. So far it has never happened on the ground.
It might be happening more often when pointed east, but I'm not
convinced that is a factor. The tech at Lancair said "the WAAS
signal is more sensitive because it uses satellites closer to the
horizon." I didn't think that was the case as I thought all the
satellites were continuously moving.
Has anyone had a similar experience? Any suggestions?
Gary Casey
Lancair ES
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Gary Casey |
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