Transponder Antenna Location

[rodsmith]

I believe that several have located their transponder antenna between the gear legs. This makes sense in that it gives you a ground plane but I wonder about the gear legs blanking out the antenna signal. Seems that is a more important issue with ADSB now. Also my trans instructions say that the antenna needs to be at least 3' from the trans to avoid RF interference which would require moving it further back.

[swpilot3]

I wrestled with the same conundrum. I read that some Maule owners did have problems with ATC picking up their transponders when it was between the gear legs. So I moved mine forward to the bottom of the boot cowl on either side of the tunnel. ADSB on one side and Transponder on the other. I was a little worried there wouldn't be enough ground plane there, but it seems to work great. ATC never complains and I always get ADSB reception.

[swpilot3]

Also because of the proximity issue with the COM antenna, I decided to put my COM antenna on top of the wing. I love crystal clear radios and hate scratchy ones! So, I wanted a very large ground plane for it.

Not sure it's the best way to do it, but my radios are crystal clear and again, ATC never complains. :-)

[Ray Strickland]

FWIW, I installed my ADSB/xponder antenna centered in the rear of the tunnel; good FAA online report. Com antennas are on tops of the wings; com checks are always, “loud and clear.”

[22LD]

I ended up placing my ADS-B antenna towards the front and my transponder antenna on an aluminum plate between the two stringers a few feet forward of the tail to keep them separated. However, my transponder is a remote and is also located behind the rear cargo bulkhead. So a fairly short run. My com antenna is on the wing.

[rodsmith]

I've decided to mount mine between the bottom stringers just aft of the bulkhead, thanks for the input. Will use some copper tape radials to enlarge the ground plane.

[Mark Moyle]

I've decided to mount mine between the bottom stringers just aft of the bulkhead, thanks for the input. Will use some copper tape radials to enlarge the ground plane.

I used 1” wide copper foil tape to create a ground field for the ELT antenna. If I had a do over I’d solder the tape to the steel stringer mount I made...let the foil tape dangle until the fabric was fully shrunk...then apply pre-shrunk tape over the copper tape...
I don’t have a better picture of the ELT antenna...

[swpilot3]

That brings up a good point that I had forgotten about. Don't put the copper foil tape on the inside of the fabric until you've completely finished the fabric with all coatings. I had shrunk my fabric and applied all the Poly Brush, then applied the foil tape. Then I applied the rest of the Poly Spray and Ploy Tone. The foil tape somehow messed up the top coats. Not sure if it was the adhesive or maybe static electricity. It's not terrible, but you can see where the foil tape is under the fabric.

[Bdflies]

When locating the ELT antenna, is there good reason to consider locating it inside the fuselage? In the event of an accident involving nosing over, ending up on your back, if the antenna is on the top of the fuselage will the ELT do anything? I really can’t say. Just a thought.
Mine is inside the fuselage and I KNOW it works. I accidentally pushed the button, in flight. Very shortly thereafter, my phone rang and I was greeted by a gentleman calling in response to an activation.

Bill

[Mark Moyle]

When locating the ELT antenna, is there good reason to consider locating it inside the fuselage? In the event of an accident involving nosing over, ending up on your back, if the antenna is on the top of the fuselage will the ELT do anything? I really can’t say. Just a thought.
Mine is inside the fuselage and I KNOW it works. I accidentally pushed the button, in flight. Very shortly thereafter, my phone rang and I was greeted by a gentleman calling in response to an activation.

Bill

I wrote Kannad asking for clarification or permission to install the antenna inside the fuselage. Not allowed was the response. I did explain the covering process did not have any component that would shield a radio signal. The shop that installed the ELT mounted the antenna opposite of the radio antenna on the wing root sheet metal which was to close to the radio antenna. The instructions specified placing it forward of the vertical stabilizer and aft of the passenger compartment. With it in that location...if you find yourself upside down...hopefully the vertical stabilizer keeps the antenna from breaking. I say breaking because mine was busted when I disassembled the aircraft to restore it. No clue how that happened..

Pretty sure Artex allows installation of the antenna inside of a tube and fabric aircraft.

[robcaldwell]

I installed my Comm, ADSB, and Xpder antennas down the belly. The ACK 406 ELT antenna is mounted inside the fuselage per their instructions. All of the other instructions I've read (Comm, ADSB, Xpder) say these locations and installations are appropriate. After reading this thread I'm now wondering if I need some copper foil tapes and such? With the Comm antenna directly on the SS Tunnel would seem adequately grounded. I've not run across anything that suggested grounding the ADSB and Xpder antennas.
IMG_1392.JPG

IMG_1394.JPG
IMG_1393.JPG
IMG_1386.JPG

[noema]

link to followup ... https://bearhawkforums.com/forum/bea...transmit-issue

[rodsmith]

I went back and read the antenna chapter in Aeroelectric Connection again. It said a ground plane disk of 5 1/2" diameter is sufficient for the transponder antenna. My mount between the stringers just happened to be 6x6". For com antenna, 6-10 radials of 1" copper tape 22" long is recommended.

[Bcone1381]

I installed my Comm, ADSB, and Xpder antennas down the belly. The ACK 406 ELT antenna is mounted inside the fuselage per their instructions. All of the other instructions I've read (Comm, ADSB, Xpder) say these locations and installations are appropriate. After reading this thread I'm now wondering if I need some copper foil tapes and such? With the Comm antenna directly on the SS Tunnel would seem adequately grounded. I've not run across anything that suggested grounding the ADSB and Xpder antennas.

Rob, I really like what you have done with antenna's! Wy doesn't the ELT antenna need a ground plane?

[robcaldwell]

I will have to go back and look at the ACK 406 instructions, but I do not recall anything about a ground plane.

[Rollie]

I put the xpnder and ADS-B antennae on the belly, offset from center enough to not interfere with the elevator control linkage, between the formers. An advantage of having a metal belly is easy mounting and a good ground plane. For the comm and GPS antennae I put them on the wings. I put the comms out from the root far enough to have a good ground plane all the way around. I've seen many planes with the antenna just a few inches from the wing root and have wondered if the lack of a good ground plane was why their radios weren't very good. The GPS ant is about 6 feet out on the left wing. The other GPS ant (I think its for the ADS-B or maybe for the G3X) is on the glareshield.

They all seem to work well. I hear traffic in patterns all over Ohio and have never had any trouble being heard. ATC sees me just fine and I get all the cool info ADS-B in has to offer. My ELT is mounted in the tail just aft of the baggage area and the antenna is mounted in the same place, inside. I haven't had to find out how well received that signal is and hopefully never will. I can't remember what brand I have, just that its a 407 and I'm sure the mounting instructions allowed it to be inside or I would have done something different.

[Steve W]

I installed my ELT similiar to what Rob is showing here. I have a Kannad Integra 406. I looked for an antenna that did not require a ground plane. Ameri King had one but is now out of business. An avionics shop advised to get the Integra, mount the antenna inside the fuselage and not to worry because it also had an internal antenna. The install test failed the external antenna. I will wait until I move the fuse outside and see if I get a reply from SAR when I do a test. They use to send me an email when I’d do the test within 5 minutes past the hour. If not, I’ll put the biggest ground plane I can in back of the baggage area and then will have to move my com antenna somewhere else.