Garmin GpsMap 396 - Flight Test #2

[Mike Spera]

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

[Jonathan Goodish]

In article et>,
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

[Ross Richardson[_1_]]

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 et>,
> 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[_1_]]

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 et>,
>> 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

[Ross Richardson[_1_]]

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 et>,
>>> 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
>
>
>

[Dave Butler[_1_]]

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."

[karl gruber[_1_]]

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 et>,
>>>> 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
>>
>>

[Ross Richardson[_1_]]

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 et>,
>>>>>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
>>>
>>>
>

[Jonathan Goodish]

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

[Mike Spera]

>
> 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

[Jonathan Goodish]

In article et>,
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

[Al[_1_]]

"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

[Dan Luke]

"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

[Jim Carter[_1_]]

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: Re: Garmin GpsMap 396 - Flight Test #2
>
> In article et>,
> 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

[J. Severyn[_1_]]

"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

[Jonathan Goodish]

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

[.Blueskies.]

"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.

[Mike Spera]

>>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