GPS failures

s_tones · #1 03-09-2007, 06:12 PM

Regarding portable GPS devices....

I did a liitle searching around in regards to GPS interference. I am finding that the G296 is fairly unreliable in congested airspace. I've had episodic failures over LAX, and in the South Bay with repeated episodes of signal loss near RHV. The outages are complete and typically 1 to 2 minutes in duration. Almost never occurs in the boonies. Curiously my panel mounted Apollo GPS seems much less problematic.

It appears that these units are suseptible to radio interference (this is Garmin's explanation).

Sooo....I'm curious, are you guys using portables and if so are you having this kind of trouble?

Jeez

Ironflight · #2 03-09-2007, 07:05 PM

For me, it depends on the antenna I'm using. I got two portable antennas with my 396 - a small one and a tiny one. When I am using the small one, I have not had any problems. When I use the tiny one (sorry for the vague descriptions - I don't have them here at home....), I lose lock every single time I flew by the big antenna farm on the southwest side of Houston (Missouri City). Never had a problem elsewhere.

Paul

CraigH@KRPH · #3 03-09-2007, 08:33 PM

I've flown in between the Cedar Hill antenna farms with the stock (little 2" stick) antenna on my 296 without any signal outage.

Did have an outage once flying near the large antenna north of Reklaw.

Mel · #4 03-09-2007, 08:39 PM

Been flying for a couple of years all over Texas and the DFW area, including the Cedar Hill towers, with my 296 and never lost signal. Of course, now that I've said that..........

gmcjetpilot · #5 03-10-2007, 05:59 AM

Yea I have never lost a signal but there are notams for GPS.

lucaberta · #6 03-12-2007, 06:42 AM

Quote:

Originally Posted by s_tones

I did a liitle searching around in regards to GPS interference. I am finding that the G296 is fairly unreliable in congested airspace. I've had episodic failures over LAX, and in the South Bay with repeated episodes of signal loss near RHV. The outages are complete and typically 1 to 2 minutes in duration.

[...]

Sooo....I'm curious, are you guys using portables and if so are you having this kind of trouble?

in the little flying I've done in South Bay a few months ago with my 296, I have never lost lock, and I've been flying quite a bit in every direction around RHV since I was preparing my single-engine commercial checkride and needed spots for my eights on pylons, chandelles and lazy eights...

I've always used the suction cup antenna in every flight, and found it quite reliable.

Could it be that your airplane has a spurious emission coming from another piece of avionics that interferes with the GPS? Maybe it's a local oscillator harmonic that you get when you tune a specific frequency on your COM or NAV, who knows...

Ciao, Luca

DBone · #7 03-12-2007, 10:17 AM

The new owner of my Cherokee contacted Garmin about the 496 losing it's signal. They told him that it's a known issue with some radios, that certain frequencies will jam the GPS signal. One of the radios on the list is the mk12d, which is the nav/com2 in that airplane.

So instead of an outside signal causing the problem, it might be something in your cockpit.

CraigH@KRPH · #8 03-12-2007, 01:49 PM

Quote:

Originally Posted by DBone

The new owner of my Cherokee contacted Garmin about the 496 losing it's signal. They told him that it's a known issue with some radios, that certain frequencies will jam the GPS signal. One of the radios on the list is the mk12d, which is the nav/com2 in that airplane.

So instead of an outside signal causing the problem, it might be something in your cockpit.

That's very interesting. The one time I lost signal with my Garmin 296 I was flying with a Mark 12D in the panel.

lucaberta · #9 03-12-2007, 02:57 PM

Quote:

Originally Posted by CraigH@KRPH

That's very interesting. The one time I lost signal with my Garmin 296 I was flying with a Mark 12D in the panel.

ah! Then, without knowing, looks like I was right!

Well, what can you expect from "Not A Radio COmpany"...

Ciao, Luca

P.S. Just kidding, don't mean to offend all of the many happy NARCO users out there.

s_tones · #10 03-13-2007, 09:17 AM

Thanks for the input on this.
Not sure what the deal is. I've got the antenna on the glare shield.
It's about 2 feet from my PCAS device. Maybe an issue?
I'm gonna try a higher gain antenna or, if possible, hooking into my external GPS antenna (which currently serves my SL60 GPS).

Jeez