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Stearman and ADS-B?

B

bob turner

Registered User
The Stearman is getting a Garmin GDL82. It is bolted in, and they called me about the antenna ground plane.

They wanted to put a 15" disc on the top wing, screw it to the rib cap strips (ouch!) and have me fabric over it.

I said WAIT! I have friends that may be able to help. I can see that disc departing on the first takeoff, wood screws and all.


So - HELP! I had them postpone the antenna installation. My thought was to put it on the sheet metal just behind the rear cockpit. It will be about ten degrees off vertical. They are panicked about it not being absolutely water line vertical. I can't see ten degrees as being a big deal.

What do you guys think?

Thanks - Bob
 
So does this thing work only in level flight? Ask them how it works in a standard rate turn, prolonged climb, prolonged nose down. The big issue I would see is shadowing but your proposed location should be fine.
DENNY
 
Mount it on top of the cowl behind the engine and forward of the wing. Another option is inside the fuselage mount a piece of al and attach the antenna to it. Might need to do some testing to find out if the stringers and tubing cause to much shadowing. They call out the 7.5 R ground plane, but how many gps antennas are mounted with no ground plane and they work just fine!



Sent from my iPad using Tapatalk
 
We’re using a Comant CI2580-200 gps/com antenna mounted just behind the rear pit, expensive but didn’t want to add more holes. Ground plane is small just enough to go between the upper stringers. Plane is just north of DC airspace and have not had any issues yet. Installed it with a Garmin 335. Transponder antenna is on the metal belly with a large ground plane. Have not gotten any calls yet regarding performance so it must be working well enough. 580D7210-BDFC-45A7-B061-19A39DD4262C.jpg
 

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The GDL-82 uses the existing transponder antenna for out and a WAAS GPS antenna for position. You shouldn't need a big ground plane to receive GPS. Since the shop wants to add the ground plane on the top wing they must be talking about GPS, right? My Cub's WAAS GPS antenna is on the left wing root fairing. It works fine.
 
Thread drift. Whew knew, right?

If I buy a GDL-82 outright it's sold for experimental use but the box is TSO'd. Garmin certified boxes MUST be installed by Garmin dealers. Not interested. Why can't I install it myself in my 180? I live in the free State of Alaska where ADS-B isn't required. What do the "rules" allow and disallow with respect to my question?
 
stewartb said:
Thread drift. Whew knew, right?

If I buy a GDL-82 outright it's sold for experimental use but the box is TSO'd. Garmin certified boxes MUST be installed by Garmin dealers. Not interested. Why can't I install it myself in my 180? I live in the free State of Alaska where ADS-B isn't required. What do the "rules" allow and disallow with respect to my question?
Click to expand...

The only issue with installing it yourself (assuming you have an A&P/IA to sign it off) is their warranty doesn’t cover.


Sent from my iPad using Tapatalk
 
Don't care about warranty so not a problem. I'd rather have a GDL-82 than a Tail Beacon so finding a way around the Garmin install requirement is appealing.
 
I think the shop is a Garmin dealer. They are pushing the GDL82. We have a J3 that needs ADS, and I am insisting on a tail beacon. Impractical on the Stearman, but I have a suitable Cub rudder.

I like what you guys are telling me. Hope Web weighs in soon. Also like the idea of behind the engine, but lots of parasitic there.
 
stewartb said:
Thread drift. Whew knew, right?

If I buy a GDL-82 outright it's sold for experimental use but the box is TSO'd. Garmin certified boxes MUST be installed by Garmin dealers. Not interested. Why can't I install it myself in my 180? I live in the free State of Alaska where ADS-B isn't required. What do the "rules" allow and disallow with respect to my question?
Click to expand...

Just a Garmin thing. Install it per instructions and it'll work fine.

Web
 
bob turner said:
The Stearman is getting a Garmin GDL82. It is bolted in, and they called me about the antenna ground plane.

They wanted to put a 15" disc on the top wing, screw it to the rib cap strips (ouch!) and have me fabric over it.

I said WAIT! I have friends that may be able to help. I can see that disc departing on the first takeoff, wood screws and all.


So - HELP! I had them postpone the antenna installation. My thought was to put it on the sheet metal just behind the rear cockpit. It will be about ten degrees off vertical. They are panicked about it not being absolutely water line vertical. I can't see ten degrees as being a big deal.

What do you guys think?

Thanks - Bob
Click to expand...

The GPS antenna has almost no wind load. Glue a piece of stainless steel window screen, about 6" diameter, to the inside of the fabric for the ground plane. Fabricate a mounting bracket to hold the antenna without distorting the fabric. GPS antenna needs to be on an upper surface like the upper wing or the top of the empennage.

The transponder antenna must be mounted on the belly. Metal to metal contact with sheet metal is best. If on fabric, do the same as with the GPS antenna, only with a larger ground plane (approx. 10"). Keep it away from stuff like the landing gear, that may shadow it. A few degrees off vertical wont matter. Up behind the engine should work well, also. I mount them on the lower part of the boot cowl on Cubs and they work well.

Web
 
Window screen is a great idea - but would require recovering a wing bay. We are planning just behind the aft cockpit with a really clear view of the sky. Upper wing and rudder are about equidistant. Without some fancy standoff it would be level with the left wing down ten degrees. Think that ten degree roll will affect it much?

On the Cub, we now are up to five J3s and a J4. Only one J3 needs ADS-B.
 
It will work just fine mounted there. Rare to find a location that is completely straight/level.

If you can go into the wing through an access panel there is no need to recover the bay. Attach the screen, fab a small mount, and mount it up. All depends on the amount of access.

Give us some pics of the antennas when they are mounted.

Web
 
Can a ground field be created using copper foil tape applied to the fabric, over the ribs through inspection rings?

Bit of a back story for the following. Back during Desert Storm...drug interdiction opps in the Virgin Islands. We were setting up a ULF radio system...the comma range was short...we added a 100’ ground field like a radials of a spiders web...easily reach Utah and DC.

My Kannada ELT required mounting between the vertical stabilizer and the cockpit. Made the ground field using copper tape...see pic. If I had a do over, would have used adhesive and glued to the inside of the tail section after recover.
7053d9f02196c0ed4ad535a3d33f5bcb.jpg



Sent from my iPad using Tapatalk Pro
 
Works just fine. A round perimeter is the best shape for a ground plane, but sometimes you work with what you have.

Only thing I see in the pic is that I would have added a couple more 'legs'.

Web
 
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