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Date: Thu, 17 May 2007 16:02:07 -0400
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From: "Jeffrey Liegner, MD" <liegner@earthlink.net>
Subject: Periodic Chelton GPS Failure...Any Ideas?
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Here's another Chelton item.

I'll be flying along and will get a "GPS Failure" announcement with 
loss of terrain info, plus DR (dead reakoning) counter.  After 1 or 2 
minues, the HITS boxes leave (as expected).  Then in three to five 
minutes the GPS signal is restored, and all is well.  In my recent 
3.5 hour flight to/from St Louis, it dropped out three times each way.

So I have looked at the antenna mounted under the top of the dash, 
just behind the panel, and it is secure and powered correctly.  I 
have checked the wiring to the Chelton and all is secure and fine.

The "GPS Failure" can occur whether the dashboard is installed or the 
GPS antenna is uncovered, meaning the particle board vinyl is not the 
obstruction.

I wonder if the location, behind the top part of the panel, with what 
seems like an excellent view of the sky, gets blanked out by the roof 
edge of the large front windscreen, reducing the satellites by a 
couple.  Is there a way to check the satellites seen by the antenna?

The GX-60 antenna located near by, equally behind the panel looking 
up through the same windscreen, does not drop out like this.

It's been doing this off/on since the beginning.  At first I thought 
I didn't think too much about it, and then I started to rely on it 
more and more, and now I learn from others that this is not a problem 
with other installations.

Your ideas?

Jeff Liegner
LIVP (N334P)