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796 Pirep & GDL 39

Kahuna

Moderatoring
Recently made some panel changes to get the 796 on it. I primarily went for this unit due to its feature set and ADSB weather integration with the GDL 39 which I also wanted to move to off XM.
The bare wire install with the docking station is a nice installation for the RV-8. I do not like things running around my cockpit like ipads and things. I preferr clean and usable.
paneldec12.jpg

I mounted the unit with screen tilt up and inward toward me more direct field of view. This is useful and makes touch screen activity easy.
I found this my first touch screen in the cockpit to be actually very nice. The speed at which you can move, select, pinch, expand, scoll etc on the unit is faster than I can mentally keep up. ADSB weather comes available at ~2k'agl.
I thought the GPS signal quality running around the hanger and house with it was going to be fine and not need an external antenna. I was wrong. In the weather at night I have twice lost gps signal while airborne. I have the remote antenna for the 796 on order. Ill add that to my low profile antenna farm on me glare shield.
I remote mounted the GDL 39 and remote mounted the external ADSB antenna to the belly of the plane. Again I dont like things running around the cockpit. Boxes in view, antennas sticking up etc. It fit nicely between the right gear tower and the baggage wall. A 90deg SMA connector on the RG400 kept a low profile install. Neat, clean, and out of the way.
I have tried both hard wire and bluetooth on the GDL 39. I found bluetooth less reliable with the GDL unit mounted a couple of metal plates away from the 796. So I recommend hard wire for remote installs between the GDL 39 and the 796.

I have had 2 issues so far with the 796.
1. Audio noise as discussed in this thread.
2. 'Inside class B airspace warnings' when Im not. I have found that it says im 'inside' when Im within 1k' above or below. I can find no settings for this. SUA alarms are either on or off. The 'airspace ahead' alarms seem pretty accurate. But for me living under a Class B coming under, in and above it, this alarm has made me act when I need not. Alarm comes on "inside class B xxx' and I act and then get frustrated. The moving map data on the altitudes of the B are fine. I think its a bug. Could be operator error. Trying to navigate the Garmin forums has been less than useful. Im running the current software.
Also, in the moving map depiction of class B, with the high res screen it would be nice if the B veils had altitude indications. So I know what they are and if Im headed towards the need to do something.

I have not been able to get any waypoint data 'in' items to work yet. Im trying to get flight plan or waypoint data from other units to send it to the 796 but the fix for this eludes me now. Im still poking away at it.

All in all I very much like the unit. It would be nice if it were tablet size. It is a big and bulky beast. But it is feature rich, provides for panel integration with weather, and has a handsome screen thats easy to use.

End of report.
 
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I thought the GPS signal quality running around the hanger and house with it was going to be fine and not need an external antenna. I was wrong. In the weather at night I have twice lost gps signal while airborne. I have the remote antenna for the 796 on order.
[...]
'Inside class B airspace warnings' when Im not. I have found that it says im 'inside' when Im within 1k' above or below. I can find no settings for this. SUA alarms are either on or off. The 'airspace ahead' alarms seem pretty accurate. But for me living under a Class B coming under, in and above it, this alarm has made me act when I need not. Alarm comes on "inside class B xxx' and I act and then get frustrated. The moving map data on the altitudes of the B are fine.
[...]
I have not been able to get any waypoint data 'in' items to work yet. Im trying to get flight plan or waypoint data from other units to send it to the 796 but the fix for this eludes me now. Im still poking away at it.

Hello Mike, glad to hear you are having success with your 796 and GDL 39. I think you provided the answer to your own first question above - remember that accurate GPS altitude measurement relies on having a reliable signal and a good antenna view of the sky. Typically a marginal installation with poor GPS reception will cause the same sort of airspace and/or terrain warning issues you describe. I suspect your problem will clear itself up once you install a remote antenna and give the unit an opportunity to receive a good signal.

As a side note, once you have your GPS reception issue cleared up, I think you might find our "Smart Airspace" feature (documented on page 63 of the aera 79x Pilot's Guide) to be useful, given your proximity to Class B airspace.

Make sure you have verified the RS-232 wiring between your GNS 430 and your aera 796 (TX on the 430 goes to RX on the aera) and configured the correct serial ports to "Aviation" on the 430 and "Aviation In" on the aera. If you are still having problems, drop us an email with your installation details using the link below and we will try to help.

- Matt
 
I get "inside SUA" or "inside Class B" warnings on my 496 and my GNC300XL when I'm physically not in them but close. Everytime I check to see exactly what's going on it's the GPS altitude that's different from the barometric altitude that's triggering the warnings. Haven't figured a way to stop that from happening.
 
On the 696 there is an "altitude buffer" setting under the alarms menu, I keep this set pretty low (200' if I recall) to eliminate these eroneous alarms.
 
I get "inside SUA" or "inside Class B" warnings on my 496 and my GNC300XL when I'm physically not in them but close. Everytime I check to see exactly what's going on it's the GPS altitude that's different from the barometric altitude that's triggering the warnings.

Yes, due to the nature of altimetry, GPS altitude and barometric altitude will seldom agree when the aircraft is not on the ground. Since a portable GPS unit does not have a way to measure barometric altitude, it must use GPS altitude for airspace detection, with the addition of a small "buffer" of a few hundred feet to help account for the difference between GPS altitude and barometric altitude. Of course, the aircraft's altimeter and the pilot's judgement should be used to make the ultimate determination about airspace (and the alerts can also be disabled by the user if desired).

I will point out that the above statement only applies to portable GPS units and is not the case with our panel-mount cockpit displays such as the G3X system, which uses its own highly accurate pressure sensor to determine the aircraft's barometric altitude.

- Matt
 
gps antenna needed?

I was wondering if you needed to buy another antenna for the 796. I thought the GDL 39 had a gps reciever in it also so by connecting it to your 796, it should take over as your gps reciever.
 
I was wondering if you needed to buy another antenna for the 796. I thought the GDL 39 had a gps reciever in it also so by connecting it to your 796, it should take over as your gps reciever.

You still need both.

One does not take over GPS duties for the other....
 
I was wondering if you needed to buy another antenna for the 796. I thought the GDL 39 had a gps reciever in it also so by connecting it to your 796, it should take over as your gps reciever.

Hello,

Take a look at this thread and it should help explain.

- Matt
 
Yes the Garmin docking station.
There is a U channel with bends to allow the dock to have some tilt up and in I made on a brake.
The docking station is great, but now that I have the external antenna, you cant just dock and undock, you have to remember to pull the antenna wire in/out.
 
Mike & Matt,

Thanks for this thread and the related one on bare wire connectivity for the Aera 796.

The data in the two threads made it a snap today as I built my panel RS232 wiring! My GDL 39 is feeding ADSB to my 795 and the 795 is feeding both my MGL V10 radio with frequencies and the TruTrak AP with tracking data.
 
tablet and gdl-39

OK.
So I am using Gamin Pilot on my Samsung Galaxy tab. I am to receive the GDL -39 on Tuesday. The tab already has a gps receiver in it but the GDL-39's receiver must be superior to it. Will it automatically take over or will i have to turn off the gps on the tablet?
 
You still need both.

One does not take over GPS duties for the other....

I have a GDL39 hard wired to my 696 and blue toothed to my iPhone and iPad. I mounted the GDL under my fiberglass cowling near the top just in front of the firewall. The GPS in the GDL reads great through the cowl and I remote mounted the ADS-B antenna on the belly. The GDL sends the GPS data to my iPad, along with the traffic and weather. Mounted in this fashion, you do not need another remote mounted GPS antenna.
-Mike Kraus
RV-4 Sold
RV-10 Flying
KitFox SS7 Building
 
I have a GDL39 hard wired to my 696 and blue toothed to my iPhone and iPad. I mounted the GDL under my fiberglass cowling near the top just in front of the firewall. The GPS in the GDL reads great through the cowl and I remote mounted the ADS-B antenna on the belly. The GDL sends the GPS data to my iPad, along with the traffic and weather. Mounted in this fashion, you do not need another remote mounted GPS antenna.
-Mike Kraus
RV-4 Sold
RV-10 Flying
KitFox SS7 Building

Actually this is a problem. The reason is that the 696 will NOT fail over to the GDL GPS data over BT or Serial. If your 696 always has clear sky then your probably fine. If its on a panel, and you end up in the right conditions (little glare shield cover, little weather to reduce signal strength etc), the 696 WILL loose GPS position and it WONT take it from the GDL stream. I had this happen before I decided an external GPS antenna on the 696/796 was required for me. I also tried covering my 796 internal antenna while the gdl 39 was clear view. I tried this with both BT and serial. It will loose GPS and fail even if the GDL has GPS lock. There is probably a reason why Garmin choose not to use the GDL GPS on a fail over but I cant think of a reason why. In most installations, the GDL is going to have good view, unless remote mounted. In most cases the 796 is going to have obstructions. Just my 2 cents.

As for other devices, its the application that determines what data it will use. Ipads, Android etc can have several GPS data streams running around available to it. It has nothing to do with which one is 'superior'.
 
I have a GDL39 hard wired to my 696 and blue toothed to my iPhone and iPad. I mounted the GDL under my fiberglass cowling near the top just in front of the firewall. The GPS in the GDL reads great through the cowl and I remote mounted the ADS-B antenna on the belly. The GDL sends the GPS data to my iPad, along with the traffic and weather. Mounted in this fashion, you do not need another remote mounted GPS antenna.
-Mike Kraus
RV-4 Sold
RV-10 Flying
KitFox SS7 Building

As long as you have the GDL39 mounted where its built in antenna can get a clear view of the sky then I agree with you, you won't need an external GDL39 GPS antenna. If you mount it where it cannot, you will need an external antenna. The OP asked about a 796, not an Ipad.

As for an external 796/696 GPS antenna, the GDL39 does not serve as the GPS for a 796 (or 696) like it can for the Ipad therefore if you do not have good satellite coverage on your 696/796, it will also need an external antenna even if it is hooked up to a GDL39 with a perfect sat lock.
 
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Down the road, the GDL 39 might provide GPS OUT. That said, I have a remote GPS connected to the GDL, since, for the time being, both the GDL 39 and the 796 need their own GPS signals.
 
While someday I think you might see the GDL39 being able to use the GPS data from the portable GPS (eliminating the need for an external GDL39 GPS antenna), I doubt you will ever see the GDL39 being able to supply GPS data to the portable GPS.

When you think about it, it would not be desirable to have the GDL39 provide GPS data to the portable GPS. One would lose the tight integration and the high update rate that is possible with the build in GPS.

Also to prevent confusing others, with the GDL39 and the Garmin Portable GPS's, the remote antenna is just that, a remote antenna. There is no GPS inside the puck.
 
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Down the road, the GDL 39 might provide GPS OUT. That said, I have a remote GPS connected to the GDL, since, for the time being, both the GDL 39 and the 796 need their own GPS signals.

Do I understand correctly.....the only purpose for the GDL39's internal GPS is so it knows its own position in order to process the traffic display?
 
Do I understand correctly.....the only purpose for the GDL39's internal GPS is so it knows its own position in order to process the traffic display?

It can also serve as an external GPS for phones and tablets over BlueTooth.

More info here.
 
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The GDL 39 GPS serves two purposes - it is used for its own calculations (weather location and traffic info) and to serve as a GPS for Bluetooth devices. Since it already sends GPS location data over Bluetooth, it suggests that a firmware update could bring this capability to the hard wired serial lines.

Given the GDL 39 serves both the certified fleet as well as the Experimental fleet, the non-hardwired configurations need to be as complete as possible. With a tablet (or 796 on a yoke) and a battery backed GDL 39 on the glare screen, a pilot in a certified aircraft can have nearly the same level of modern equipment we can build into our panels. :D
 
Update Audio Noise

I found the culprit on my headset noise after installing my 796.
I have a music input jack, 1/8" little guy mounted on the gear tower since day one.
This jack is not isolated from the tower. As noted before, I wired the 796 audio to the back side of this jack, in parallel with the rest of the audio inputs for music. I never had any noise until installing the 796.
I have had to replace this jack a couple of times. Its not a very robust jack for the amount of use it gets. So after figuring out this was the culprit (unscrewed it while flying along and pushed it out of its mount, ignition noise went away immediately), I removed it and replaced with a 1/4" jack with isolators. This has cured my problem. Plus the 1/4" jack with a 90 deg adapter is a much more robust jack and should last a lot longer.
 
I absolutely love the 796. I have mine mounted in my LSA and would love to add one into the panel of the RV-12 I am building. I fly all the time around Denver and get the you are in Class B warning popping up sometimes. I can be as much as 1000 feet below it and still get the warning. It has a strange anomaly on lateral limits too where it will occasionally warn when there isn't even a class B shelf above me. This happened with my old 496 and the 796. It is most prevalent closer to the mountains for some reason. I had a remote antenna for the 496 and have one for the 796 as well. It is a minor issue overal though. I am always talking to Denver and usually cleared into the Bravo anyway.

I also had some issue with the unit randomly restarting if you zoomed around too much too quickly but they seem to have fixed that with a firmware update. The other issue I have seen is not great support for Mac's when it comes to updating charts. I find that if I don't update all the states but rather choose the coverage area the charts that get downloaded end up corrupt using the Mac. I have to run VMWare to get around this. Again it is a pain but the unit makes it well worth it.

I have flown several longer cross countries with the 796 and it is just incredible. The terrain feature is really nice, especially out here where the terrain can be a significant feature. The weather is outstanding as well. I am trying to make the decision on the GDL-39 right now. I have XM and renew in a couple weeks right before I leave for Sebring FL for the LSA expo. The only issue I have with it is the battery life. It would be nice to not have to have more wires running to the 12v plug. I know I can bare wire it in but that means another letter of authorization to make the mod. I prefer to see if it works first. Of course on top of the great visibility of the 796, the XM radio is a godsend on long cross countries too. Between the weather and radio, I just love it.
 
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