Garmin GpsMap 396 - Flight Test

Mike Spera wrote:
snip
Not exactly confidence inspiring. This unit may be a bad one. It
happens, I just wish it were a complete failure instead of this
intermittent crap.

I'll report on its progress.

Mike

Funny you should mention this. My 396 GPS reception has been flaky
lately too. Normally, the stick antenna would give me 4-5 sats indoors,
which is pretty good, while the external (powered) antenna would lock 8+
sats at higher signal indications in the same location (understandable
since it has a preamp that's powered through the coax).

Shortly after I upgraded to firmware 3.0 or 3.1 (can't remember exactly)
I took a trip to SC and had the external antenna just completely crap
out on me. No sat reception at all. I replaced it with the stick and
that got me three sats...enough for 2D positioning.

I initially attributed it to poor satellite positioning (there are times
when all the sats are behind the aircraft and the aircraft structure
shields the yoke/glareshield area), but it didn't comfort me to realize
that the Garmin 430 in the panel was locked to 10 sats with signals
pegged high.

Just today, after upgrading to 3.2, the problem isn't as bad, but the
external antenna doesn't seem to be doing the same job as it used to.

The release notes for the last several releases mention that they've
been screwing with reception issues for the XM receiver, but I wonder if
they messed something up with the GPS component firmware.

So, who wants to open a case with Garmin? If I can find two seconds to
rub together, I just might...this thing WAS running beautifully in the
2.x firmware days. I'm almost tempted to downgrade and test my theory.

-Doug

--------------------
Doug Vetter, ATP/CFI

http://www.dvatp.com
--------------------

You know, with the reception problems I am reading about here, I think I
will stick with my GPS 195 a while longer. I always get a lock with a
minimum of six to eight sats.

In article
,
john smith wrote:

You know, with the reception problems I am reading about here, I think I
will stick with my GPS 195 a while longer. I always get a lock with a
minimum of six to eight sats.

I don't have reception problems, and am puzzled as to why some users are
experiencing them. I am using the GA26 remote antenna, but this is
supposedly a "low power" antenna, so I'm not sure if that is a factor or
not (Garmin uses active antennas.) I have an unused GA56 on top of the
airplane, and that does seem to result in stronger signals, but part of
that could be the more ideal placement, with an unobstructed view of the
sky.


JKG

"Jonathan Goodish" wrote:
,
john smith wrote:

You know, with the reception problems I am reading about here, I think I
will stick with my GPS 195 a while longer. I always get a lock with a
minimum of six to eight sats.

I don't have reception problems...

Nor I. I get the same reception performance--or better--with the 396 as I
have with all my previous Garmins.

I do remember that my 195 had trouble locking if activated while in motion.
The 396 is not bothered.

--
Dan
C172RG at BFM

In article ,
"Dan Luke" wrote:
I don't have reception problems...

Nor I. I get the same reception performance--or better--with the 396 as I
have with all my previous Garmins.

In Mike's case, it sounds like an interference issue to me.


JKG

Very possible... He needs to get out of the airport area and turn off
thenav/com radios and the transponder and see what happens... If that
is no good, then turn off the master switch and the alternator... If
still no good, then it is the 396...

denny

Actually, I did try a few tests. When switching to my second com and
transmitting, it did the same thing. Down to zero on every sat.
Relocating the GPS antenna to the back seats near the window or anywhere
else made no difference when transmitting. It did seem a little better
for reception on the right side of the glareshield (opposite side from
the XM antenna). Turning off all the radios and the complete electrical
system had no effect. I still had flaky reception.

Once I have my other GPS units side by side with this one, I should be
able to isolate whether it is a plane/radio or specific GPS problem.

Thanks to all for suggestions,
Mike

Very possible... He needs to get out of the airport area and turn off
thenav/com radios and the transponder and see what happens... If that
is no good, then turn off the master switch and the alternator... If
still no good, then it is the 396...

denny

Dan Luke wrote:
"Jonathan Goodish" wrote:

,
john smith wrote:


You know, with the reception problems I am reading about here, I think I
will stick with my GPS 195 a while longer. I always get a lock with a
minimum of six to eight sats.

I don't have reception problems...


Nor I. I get the same reception performance--or better--with the 396 as I
have with all my previous Garmins.

ditto.


I do remember that my 195 had trouble locking if activated while in motion.
The 396 is not bothered.

Yes, the ol' 196 would take noticeably longer to initialize if powered up
somewhere other than where it went to sleep, even a few feet. Not so the 396.

Funny you should mention this. My 396 GPS reception has been flaky
lately too.

I went out again and tried a few things. I noticed on both days that I
would get 8-10 sats pinned at the top while stationary. Once I started
rolling, most would come down a bit and jump up and down some. After
rotation and climbing, all sats were lost and the thing lost its lock. I
landed and tried again. Same result. O.K. So I cannot depend on it
during a climb?

Next, I tried moving the antenna around and switching to the stub. It
seemed a little better placing the antenna on the right side of the
glareshield opposite the XM. Turning in some directions made for better
or worse reception. However, WAAS was lost going some ways and regained
randomly along that path or by turning. This seems flaky.

Then I tried something I never really tried with my other GPS units. I
watched the sat page while transmitting. All sat bars marched down to
the bottom and disappeared in about 5-7 seconds. Release the transmit
button and they immediately came back up to where they were. So, now I
cannot trust this thing while transmitting?

I will bring along my Lowrance Airmap 1000 and monitor the sat page
during the various aspects of flight and compare it to the Garmin.
Perhaps the Lowrance is just as weak and I did not notice (because it
never lost a lock so I had no reason to look). For laughs, I may also
bring along one of my several Apollo 920 units and watch its
performance. The Apollo never lost its lock in 7 years of use.

Mike

"Mike Spera" wrote:


Then I tried something I never really tried with my other GPS units. I
watched the sat page while transmitting. All sat bars marched down to the
bottom and disappeared in about 5-7 seconds. Release the transmit button
and they immediately came back up to where they were. So, now I cannot
trust this thing while transmitting?

It could still be you have a faulty 396, but it sounds like it's you have a
radio/electrical problem. I had a Cessna NAV/COM that did the same thing to
my old 295. Swapping the radio with another one solved the problem. You may
also have a leaky antenna cable shield.

Is that the only COM radio you have? What happens when you power it off and
use another transmitter? If the same thing happens, you may have a
grounding problem in the airplane.

Trying the other portable GPS is a good test. If you're lucky, the Lowrance
will work ok and prove you have a bad Garmin. If not, I still recommend
that you turn off EVERYTHING electrical in the airplane and see how the 396
receives satellites. Then, add stuff back in one at a time until you
observe any loss of signal.

Good luck with your gremlin.

--
Dan
C172RG at BFM