Garmin GpsMap 396 - Flight Test #2

In article . net,
Mike Spera wrote:
O.K., if there is an EMI issue, why does it only affect the Garmin? The
Lowrance and Apollo units were completely unphased by the transmissions
and never lost their lock during the entire test flight (and the
previous 8 years of use). I tested them all side by side. The Garmin sat
bars were hopping all around in straight and level flight while the
older units were stone solid.

Something specific to newer GPS receivers?


I don't know about that, but I do know that Garmin uses an active
antenna, whereas many others (including Lowrance) use a passive antenna.
Not sure how much difference this makes for RFI, but I suppose that any
interference could be amplified from the antenna.

I can tell you that I haven't had any GPS reception problems with my
396, and I have a fairly old panel (King KX170Bs, etc.)

It's unclear whether you've called Garmin Tech Support; if you haven't,
I would highly recommend it. If you aren't going anywhere with them,
call back or escalate until you are talking to someone who can help
narrow the cause(s) of your problem.



JKG

"Mike Spera" wrote in message
ink.net...


I'm sorry to say, it sounds like you have an EMI issue. If you key the
mic and the sats drop, that's a pretty good indication of at least one
problem.

Upgrading the software to the latest code should go without saying.
Garmin will insist that you do that before they will help you
troubleshoot such an issue. Garmin did make GPS reception improvements
in some later software releases.

O.K., if there is an EMI issue, why does it only affect the Garmin? The
Lowrance and Apollo units were completely unphased by the transmissions
and never lost their lock during the entire test flight (and the previous
8 years of use). I tested them all side by side. The Garmin sat bars were
hopping all around in straight and level flight while the older units were
stone solid.

Something specific to newer GPS receivers?

Thanks,

Mike

Hi Mike,

did you try the "almanac" fix as suggested by Dan?

I inquired to Garmin Tech support about our problems and got the
following response about clearing the almanac. Probably worth a shot.

--Dan


========================
Problem:
I had a problem with satellite reception over the weekend. In
disucssing this with other GPSMAP 396 users, including one who recently
upgraded to firmware 3.20, it seems they are experiencing similar
problems as well.
(i.e. intermittent GPS satellite loss) I have a GPSMAP 195 and have
never had a satellite signal issue. Is this a known problem? Will there
be a firmware fix?
===============================
Thank you for contacting Garmin.

As the GPS uses a satellite almanac of data to track the satellites,
corruption of this almanac will cause the unit to drop the satellite
signals. To correct(erase) the almanac, turn the unit off. Press and
hold the OUT button while turning the GPS on. When the GPS powers on,
release the buttons and let it acquire the satellite signals to start
rebuilding the almanac.

If you have any other questions, please let me know.

Best Regards

"Mike Spera" wrote:


I'm sorry to say, it sounds like you have an EMI issue. If you key the
mic and the sats drop, that's a pretty good indication of at least one
problem.

Upgrading the software to the latest code should go without saying.
Garmin will insist that you do that before they will help you
troubleshoot such an issue. Garmin did make GPS reception improvements
in some later software releases.

O.K., if there is an EMI issue, why does it only affect the Garmin? The
Lowrance and Apollo units were completely unphased by the transmissions
and never lost their lock during the entire test flight (and the previous
8 years of use). I tested them all side by side. The Garmin sat bars were
hopping all around in straight and level flight while the older units were
stone solid.

Something specific to newer GPS receivers?

Could be. I'm now suspicious of your particular 396. It might have some
fault that makes it more than normally susceptible to RFI. I can attest
that mine has been solid for about 50 hours of use in the airpane.

It's going to be very interesting to see how a replacement 396 performs.

--
Dan
C172RG at BFM

But Mike gets dropped sats even without keying the mic and with all
electrics off. That can't be totally EMI. It has to be a bad 396 because
his other two old faithfuls hung in there throughout the flight.

-----Original Message-----
From: Jonathan Goodish ]
Posted At: Friday, July 07, 2006 08:11
Posted To: rec.aviation.owning
Conversation: Garmin GpsMap 396 - Flight Test #2
Subject: Garmin GpsMap 396 - Flight Test #2

In article . net,
Mike Spera wrote:
I never did check the SW level of the old unit. I missed that one
bit of
data. I will try the new one and check the SW level. If it performs
like
the old one, I will upgrade and try again. If it still does not work
after the upgrade, I'll give Garmin a call before taking the unit
back
for a refund.


I'm sorry to say, it sounds like you have an EMI issue. If you key
the
mic and the sats drop, that's a pretty good indication of at least one
problem.

Upgrading the software to the latest code should go without saying.
Garmin will insist that you do that before they will help you
troubleshoot such an issue. Garmin did make GPS reception
improvements
in some later software releases.



JKG

"Jim Carter" wrote in message
. com...
But Mike gets dropped sats even without keying the mic and with all
electrics off. That can't be totally EMI. It has to be a bad 396 because
his other two old faithfuls hung in there throughout the flight.

All the electrics are off except the magnetos. I suppose the spark at the
mag points and the spark plugs could be generating EMI that affects the 396,
especially if a shield to one of the plugs is broken so that the return path
takes a route in the airframe that is close to the 396 antenna...... But
I'm really grasping at straws here.

John Severyn
@KLVK

In article ,
"Jim Carter" wrote:

But Mike gets dropped sats even without keying the mic and with all
electrics off. That can't be totally EMI. It has to be a bad 396 because
his other two old faithfuls hung in there throughout the flight.

Not necessarily. Garmin uses a different (active) antenna. Not sure
about Magellan, but Lowrance uses a passive antenna. It is possible
that the active antenna is amplifying noise that has infiltrated the
system, though that's probably a stretch. Mike definitely has a RFI
issue with the coms, though, because he can repeat the failure reliably
when he transmits.



JKG

"Jonathan Goodish" wrote in message
...
In article ,
"Jim Carter" wrote:

But Mike gets dropped sats even without keying the mic and with all
electrics off. That can't be totally EMI. It has to be a bad 396 because
his other two old faithfuls hung in there throughout the flight.

Not necessarily. Garmin uses a different (active) antenna. Not sure
about Magellan, but Lowrance uses a passive antenna. It is possible
that the active antenna is amplifying noise that has infiltrated the
system, though that's probably a stretch. Mike definitely has a RFI
issue with the coms, though, because he can repeat the failure reliably
when he transmits.



JKG

RFI issue is with the COMMS and the Garmin. RFI was no issue with the other two GPS receivers listed.

Not necessarily. Garmin uses a different (active) antenna. Not sure
about Magellan, but Lowrance uses a passive antenna. It is possible
that the active antenna is amplifying noise that has infiltrated the
system, though that's probably a stretch. Mike definitely has a RFI
issue with the coms, though, because he can repeat the failure reliably
when he transmits.

The Lowrance has "Remote Amplifying Antenna" printed on it. Does that
not make it an active antenna? I thought passives did not contain amps.

Whazzup?

thanks,
Mike