Garmin GpsMap 396 - Flight Test #2

So I set up my other 2 GPS units in the cockpit and put their external
antennas right next to the Garmin. The Lowrance Airmap 1000 and an old
Apollo 920+ showed 5-9 sats up near the 80%. The Garmin showed 8+ sats
pinned at the top and one or two more at 50%. Immediately after liftoff
the Garmin marched down to zero on all sats and lost its lock. The other
2 units stayed strong. The Lowrance got better reception in flight than
on the ground.

After leveling, the Garmin reacquired a lock. 10 seconds later, WAAS
locked. Hit the transmit button and the Garmin again marched down to
zero on all sats and immediately popped back up when the mic button was
released. The 2 old units never blinked the entire time during transmission.

Take up a SE heading, the Garmin goes to zero on all sats and stays
there until I turn to some other direction. The other 2 units keep a
strong lock.

Tried every possible position in the cabin and the Garmin still blanked
out. The other 2 had different sat bars but never went below 80% with 6+
sats. Unplugged all units from ships power and tried the tests on
batteries. Same result. Flew outside the Mode C veil and shut off the
electrical system. Same results. Tried different power settings and it
did not seem to make any difference

When powered back for landing with the nose pushed over, the Garmin
again went out to lunch. The other 2 remained locked and strong.

Brought the whole box o' stuff back to JA Air center after calling them
to obtain agreement for a swap. They swapped the unit and external
antenna and kept the rest of the accessories for the new unit. Made
sense. They did try to talk me into upgrading the software before
agreeing to a swap. I said I would upgrade AFTER we swapped if the
problem remained. After the swap, I would have confidence it is not one
particular bad unit. So, I am not chasing a gremlin that turns out to be
a defective unit.

I would love to go up tonight and try the new unit, however, the
President found it necessary to bung up not one, but 2 30 MILE TFRs FOR
HIS FREAKIN BIRTHDAY PARTY! FOR 24 HOURS! Lovely.

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 really do love the weather data. I am hoping I can find the gremlin
and keep the 396.

Will report back late Friday or Saturday.

Mike

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

This is a known problem with Com transmitters and GPS receivers,
especially with the older units. If I remember it is something like the
10th or 11th harmonic of the COM that can interfer with the GPS. I first
noticed it with my old Appolo 2001 that on certain transmit frequencies
the GPS would blank out. I contacted the manufacturer and they provided
me a paper which included something like 20 frequencies in the aircraft
band that could cause this. I check them and sure enough some did and
others did not. Also it is/was how close the two antennas are.

Ross

Jonathan Goodish wrote:

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

The main difference between a KX-155 and a KX-155A is that the later was
designed and built after GPS was in use. The "A" models do not interfere
with GPS.

ALL the older radios, straight 155, 170 series will interfere with GPS. That
is the reason one has to test certain frequencies in an IFR GPS
installation. One can be sure that if there is a straight 155,or 170 and
older radio in your airplane, you will not be able to pass that test. Those
who have, have "parker penned" the installation, regardless of how many
'notch" filters have been installed.......that's just pure BS.

Best,
Karl
"Curator"


"Ross Richardson" wrote in message
...
This is a known problem with Com transmitters and GPS receivers,
especially with the older units. If I remember it is something like the
10th or 11th harmonic of the COM that can interfer with the GPS. I first
noticed it with my old Appolo 2001 that on certain transmit frequencies
the GPS would blank out. I contacted the manufacturer and they provided me
a paper which included something like 20 frequencies in the aircraft band
that could cause this. I check them and sure enough some did and others
did not. Also it is/was how close the two antennas are.

Ross

Jonathan Goodish wrote:

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

Oh, but my KLN-89/B was flight tested by the FAA and installer. It has
to be right. I have Dual MK-12Ds.

karl gruber wrote:

The main difference between a KX-155 and a KX-155A is that the later was
designed and built after GPS was in use. The "A" models do not interfere
with GPS.

ALL the older radios, straight 155, 170 series will interfere with GPS. That
is the reason one has to test certain frequencies in an IFR GPS
installation. One can be sure that if there is a straight 155,or 170 and
older radio in your airplane, you will not be able to pass that test. Those
who have, have "parker penned" the installation, regardless of how many
'notch" filters have been installed.......that's just pure BS.

Best,
Karl
"Curator"


"Ross Richardson" wrote in message
...

This is a known problem with Com transmitters and GPS receivers,
especially with the older units. If I remember it is something like the
10th or 11th harmonic of the COM that can interfer with the GPS. I first
noticed it with my old Appolo 2001 that on certain transmit frequencies
the GPS would blank out. I contacted the manufacturer and they provided me
a paper which included something like 20 frequencies in the aircraft band
that could cause this. I check them and sure enough some did and others
did not. Also it is/was how close the two antennas are.

Ross

Jonathan Goodish wrote:


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

karl gruber wrote:
The main difference between a KX-155 and a KX-155A is that the later was
designed and built after GPS was in use. The "A" models do not interfere
with GPS.

ALL the older radios, straight 155, 170 series will interfere with GPS. That
is the reason one has to test certain frequencies in an IFR GPS
installation. One can be sure that if there is a straight 155,or 170 and
older radio in your airplane, you will not be able to pass that test.

I'm sure Karl meant to say "...you will possibly not be able to pass that test."

That test flight was bogus. Your installer probably didn't have a clue, and
the FAA for SURE didn't.

Karl


"Ross Richardson" wrote in message
...
Oh, but my KLN-89/B was flight tested by the FAA and installer. It has to
be right. I have Dual MK-12Ds.

karl gruber wrote:

The main difference between a KX-155 and a KX-155A is that the later was
designed and built after GPS was in use. The "A" models do not interfere
with GPS.

ALL the older radios, straight 155, 170 series will interfere with GPS.
That is the reason one has to test certain frequencies in an IFR GPS
installation. One can be sure that if there is a straight 155,or 170 and
older radio in your airplane, you will not be able to pass that test.
Those who have, have "parker penned" the installation, regardless of how
many 'notch" filters have been installed.......that's just pure BS.

Best,
Karl
"Curator"


"Ross Richardson" wrote in message
...

This is a known problem with Com transmitters and GPS receivers,
especially with the older units. If I remember it is something like the
10th or 11th harmonic of the COM that can interfer with the GPS. I first
noticed it with my old Appolo 2001 that on certain transmit frequencies
the GPS would blank out. I contacted the manufacturer and they provided
me a paper which included something like 20 frequencies in the aircraft
band that could cause this. I check them and sure enough some did and
others did not. Also it is/was how close the two antennas are.

Ross

Jonathan Goodish wrote:


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

Now, what would make you think that

karl gruber wrote:

That test flight was bogus. Your installer probably didn't have a clue, and
the FAA for SURE didn't.

Karl


"Ross Richardson" wrote in message
...

Oh, but my KLN-89/B was flight tested by the FAA and installer. It has to
be right. I have Dual MK-12Ds.

karl gruber wrote:


The main difference between a KX-155 and a KX-155A is that the later was
designed and built after GPS was in use. The "A" models do not interfere
with GPS.

ALL the older radios, straight 155, 170 series will interfere with GPS.
That is the reason one has to test certain frequencies in an IFR GPS
installation. One can be sure that if there is a straight 155,or 170 and
older radio in your airplane, you will not be able to pass that test.
Those who have, have "parker penned" the installation, regardless of how
many 'notch" filters have been installed.......that's just pure BS.

Best,
Karl
"Curator"


"Ross Richardson" wrote in message
...


This is a known problem with Com transmitters and GPS receivers,
especially with the older units. If I remember it is something like the
10th or 11th harmonic of the COM that can interfer with the GPS. I first
noticed it with my old Appolo 2001 that on certain transmit frequencies
the GPS would blank out. I contacted the manufacturer and they provided
me a paper which included something like 20 frequencies in the aircraft
band that could cause this. I check them and sure enough some did and
others did not. Also it is/was how close the two antennas are.

Ross

Jonathan Goodish wrote:



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

In article ,
Ross Richardson wrote:

This is a known problem with Com transmitters and GPS receivers,
especially with the older units. If I remember it is something like the
10th or 11th harmonic of the COM that can interfer with the GPS. I first
noticed it with my old Appolo 2001 that on certain transmit frequencies
the GPS would blank out. I contacted the manufacturer and they provided
me a paper which included something like 20 frequencies in the aircraft
band that could cause this. I check them and sure enough some did and
others did not. Also it is/was how close the two antennas are.


I really meant to say "RFI." You are correct. I seem to remember
reading a warning in the Garmin 430 installation manual that mentioned
routing the antenna cable as far away from the com installation as
possible.



JKG

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