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Dan[_1_]
August 5th 06, 09:36 PM
As a followup to my previous post on 396 GPS reception problems, has
anyone noticed GPS reception issues around the Chandler, AZ airport?
As soon as I leave the ground, I seem to always lose satellite lock on
my Garmin 396. I lose satellite lock like crazy in the pattern. Leave
the area, and everything is fine. Throughout 2 cross countries, not one
problem with the satellite. Get near CHD (and once on the ground at
FFZ) and problems are guaranteed.

It's not the on-board radios, since this has happend in 2 different
aircraft, and in one of them, the only radio in use was a GNS 430.
(430 did not lose sat lock).

Maybe there is some kind of interferance, although this pattern of
behaviour is very strange!

--Dan

Mike[_5_]
August 6th 06, 12:17 AM
"Dan" > wrote in message
ups.com...
> As a followup to my previous post on 396 GPS reception problems, has
> anyone noticed GPS reception issues around the Chandler, AZ airport?
> As soon as I leave the ground, I seem to always lose satellite lock on
> my Garmin 396. I lose satellite lock like crazy in the pattern.
> Leave
> the area, and everything is fine. Throughout 2 cross countries, not
> one
> problem with the satellite. Get near CHD (and once on the ground at
> FFZ) and problems are guaranteed.
>
> It's not the on-board radios, since this has happend in 2 different
> aircraft, and in one of them, the only radio in use was a GNS 430.
> (430 did not lose sat lock).
>
> Maybe there is some kind of interferance, although this pattern of
> behaviour is very strange!
>
> --Dan

You might report it to ATC or FSS although depending on the controller
they might not know what to do with it. The FAA actually tracks GPS
anomalies.

Dan[_1_]
August 6th 06, 02:26 AM
I found the problem! Those with 396s might be interested in the
solution.

I setup the 396 w/ external antenna in the car and proceeded to drive
to the airport. Satellite signal was great for about 15 miles until I
arrived at an intersection in the city. All of the sudden, signal
strengths quickly dropped to zero and I got the "signal lost"
message. A half mile or so later, all was fine. Strange...

Continuing towards the airport, I arrived at another spot where the
signal dropped to zero. It was in an especially open area, so
obstructions were not the problem. I quickly pulled over. The signal
stayed at zero, and I looked around to see what would be causing it.
Sure enough, about a quarter mile away were two cell towers with a
clear line of sight to my vehicle. If I moved such that a building was
between me and the cell towers, signal came back. If I switched to the
"stick" antenna, signal came back as well.

So, the problem is the external antenna has some kind of reaction when
in close proximity and line of sight to certain cell towers. Just like
the kind of situation right after takeoff at CHD, and also in the
pattern. At high altitudes, it's not an issue, just in the pattern
near this area. This also explains why sat lock is rock solid in
cruise and out in the boonies.

I did further testing which confirms my theory. Seems I'll be
requesting a new external antenna from Garmin, or purchasing a 3rd
party external antenna. For now, I'll just use the "stick"
antenna. This was certainly unexpected.

--Dan


Dan wrote:
> As a followup to my previous post on 396 GPS reception problems, has
> anyone noticed GPS reception issues around the Chandler, AZ airport?
> As soon as I leave the ground, I seem to always lose satellite lock on
> my Garmin 396. I lose satellite lock like crazy in the pattern. Leave
> the area, and everything is fine. Throughout 2 cross countries, not one
> problem with the satellite. Get near CHD (and once on the ground at
> FFZ) and problems are guaranteed.
>
> It's not the on-board radios, since this has happend in 2 different
> aircraft, and in one of them, the only radio in use was a GNS 430.
> (430 did not lose sat lock).
>
> Maybe there is some kind of interferance, although this pattern of
> behaviour is very strange!
>
> --Dan

Ron Rosenfeld
August 6th 06, 03:34 AM
On 5 Aug 2006 13:36:47 -0700, "Dan" > wrote:

>As a followup to my previous post on 396 GPS reception problems, has
>anyone noticed GPS reception issues around the Chandler, AZ airport?
>As soon as I leave the ground, I seem to always lose satellite lock on
>my Garmin 396. I lose satellite lock like crazy in the pattern. Leave
>the area, and everything is fine. Throughout 2 cross countries, not one
>problem with the satellite. Get near CHD (and once on the ground at
>FFZ) and problems are guaranteed.
>
>It's not the on-board radios, since this has happend in 2 different
>aircraft, and in one of them, the only radio in use was a GNS 430.
>(430 did not lose sat lock).
>
>Maybe there is some kind of interferance, although this pattern of
>behaviour is very strange!
>
> --Dan

If the 430 did not lose lock, I'd guess there's some problem with your 396
or its antenna.


Ron (EPM) (N5843Q, Mooney M20E) (CP, ASEL, ASES, IA)

August 6th 06, 03:55 AM
"Dan" > wrote:
> As a followup to my previous post on 396 GPS reception problems, has
> anyone noticed GPS reception issues around the Chandler, AZ airport?
> As soon as I leave the ground, I seem to always lose satellite lock on
> my Garmin 396. I lose satellite lock like crazy in the pattern. Leave
> the area, and everything is fine. Throughout 2 cross countries, not one
> problem with the satellite. Get near CHD (and once on the ground at
> FFZ) and problems are guaranteed.
>
> It's not the on-board radios, since this has happend in 2 different
> aircraft, and in one of them, the only radio in use was a GNS 430.
> (430 did not lose sat lock).
>
> Maybe there is some kind of interferance, although this pattern of
> behaviour is very strange!

I fly out of CHD. I have a 296 GPS and use the external antenna (mounted
in my back window). I have never had one problem losing satellite
reception with this arrangement. I always had interrupted coverage with
the stick antenna, however.

Cub Driver
August 6th 06, 11:06 AM
On 5 Aug 2006 13:36:47 -0700, "Dan" > wrote:

> Get near CHD (and once on the ground at
>FFZ) and problems are guaranteed.

My first GPS flying was with a unit belonging to my daughter, a
sailor. It regularly lost signal over PSM, the former Pease Air Force
Base; I used to suspect a left-over top secret ray to blind incoming
missiles. I live a couple miles across Great Bay from PSM, and the
only way I could get that GPS to find a signal was to set it on the
dock for half an hour. Very odd.

But once I acquired a GPS of my own, that problem disappeared. It
seemed to have been peculiar to that unit.



-- all the best, Dan Ford

email: usenet AT danford DOT net

Warbird's Forum: www.warbirdforum.com
Piper Cub Forum: www.pipercubforum.com
In Search of Lost Time: www.readingproust.com

.Blueskies.
August 6th 06, 01:03 PM
"Dan" > wrote in message oups.com...
:I found the problem! Those with 396s might be interested in the
: solution.
:
: I setup the 396 w/ external antenna in the car and proceeded to drive
: to the airport. Satellite signal was great for about 15 miles until I
: arrived at an intersection in the city. All of the sudden, signal
: strengths quickly dropped to zero and I got the "signal lost"
: message. A half mile or so later, all was fine. Strange...
:
: Continuing towards the airport, I arrived at another spot where the
: signal dropped to zero. It was in an especially open area, so
: obstructions were not the problem. I quickly pulled over. The signal
: stayed at zero, and I looked around to see what would be causing it.
: Sure enough, about a quarter mile away were two cell towers with a
: clear line of sight to my vehicle. If I moved such that a building was
: between me and the cell towers, signal came back. If I switched to the
: "stick" antenna, signal came back as well.
:
: So, the problem is the external antenna has some kind of reaction when
: in close proximity and line of sight to certain cell towers. Just like
: the kind of situation right after takeoff at CHD, and also in the
: pattern. At high altitudes, it's not an issue, just in the pattern
: near this area. This also explains why sat lock is rock solid in
: cruise and out in the boonies.
:
: I did further testing which confirms my theory. Seems I'll be
: requesting a new external antenna from Garmin, or purchasing a 3rd
: party external antenna. For now, I'll just use the "stick"
: antenna. This was certainly unexpected.
:
: --Dan
:


Probably the magnets in the external antenna are pulling in those cell signals.... ;-)

Dan[_1_]
August 7th 06, 10:46 PM
I was on the phone with Garmin for about 30 seconds and they said this
was a known issue with some antennas and they would be sending me a new
one ASAP. Great customer service.

--Dan


Dan wrote:
> As a followup to my previous post on 396 GPS reception problems, has
> anyone noticed GPS reception issues around the Chandler, AZ airport?
> As soon as I leave the ground, I seem to always lose satellite lock on
> my Garmin 396. I lose satellite lock like crazy in the pattern. Leave
> the area, and everything is fine. Throughout 2 cross countries, not one
> problem with the satellite. Get near CHD (and once on the ground at
> FFZ) and problems are guaranteed.
>
> It's not the on-board radios, since this has happend in 2 different
> aircraft, and in one of them, the only radio in use was a GNS 430.
> (430 did not lose sat lock).
>
> Maybe there is some kind of interferance, although this pattern of
> behaviour is very strange!
>
> --Dan

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