Antenna

[Flybyjim]

I am at a point of deciding what antennas I need and where to put them along with the OAT probe. I am going to be using a G3X, GTX-45R transponder, GTR-200 panel mount radio. So the questions are, what have others used, the location of mounting and if flying how it all worked out.

[896tr]

Even though I had to sell my plane before I got it finished I made a vhf di-pole antenna and mounted it in the vertical stabilizer before I covered the plane. I had reports that even from inside my garage on a handheld it could be heard better than most of the other planes on the ground at the airpark that I lived at. Hell yes I was proud of that!

[jiott]

I have a bent whip radio antenna on the bottom of the fuse, RH side. The transponder antenna is on the bottom of the fuse, LH side. Both work very well. They are mounted on the two antenna mount plates that come standard on the SS7 fuse. My GPS antenna puck is mounted on the top side just behind the turtle deck. It also works great, looking up at the satellites in the sky. My ADS_B IN antenna is on the bottom of the fuse, in the center, just behind the stainless steel firewall piece that is bent back along the bottom.

Even though everything works fine where they are now, if I were to do it again I would mount the GPS puck inside, under the turtle deck, looking up. The comm antenna would go in the classic location on topside behind the turtle deck, and the ADS_B IN antenna would go on the bottom antenna pad, RH side.

[Flybyjim]

Thank you for the replies. Jim, you said you would change the locations, I am wondering why.

Personally, I was thinking about the comm antenna going on the top behind the turtle deck, transponder on the right side antenna tray and I was unsure about the GPS/ADSB in/out antennas. I have mounted the remote transponder beside the roll servo on the left antenna tray.

[PaulSS]

I am merely regurgitating what advice I've gleaned from reading various fora regarding antenna location but the learned opinion urges caution with the transponder and ADSB. Now, I know you chaps in the US have the UAT frequency and, therefore, this may be a moot point BUT if you're using 1090 MHz for the ADSB then you need to consider that this is the same frequency as the transponder and those beasties have quite a powerful transmission. Apparently we should ensure there's at least a 1/4 wavelength separation twixt the antennae but greater if possible. I'm not sure this presents any problems for the location as the wavelength is pretty short (0.275m) but it MAY be worth considering, lest your transponder totally swamps your ADSB receiver with its super powers.

As far as the type of antenna required, you can use the TED-type for both transponder and ADSB and they are pretty reasonably priced:

http://www.aircraftspruce.com/catalo...clickkey=23156

[jrevens]

For what it’s worth, I welded on a mounting plate for my comm antenna between the turtledeck and the vertical fin. I bought the kit before the factory was putting their mounting plates directly behind the turtledeck along with the curved steel tube for the “razorback” look. So, my antenna is in a little different position than the new ones... not so close to the rear edge of the turtledeck. My “razorback” curve is therefore a little different also. My transponder antenna is on the belly mounting plate behind the passenger seat. My ADS-B antenna is on the bottom of a panel I mounted behind the baggage compartment, inside the fuselage structure. GPS antenna is front and center just under the instrument panel glareshield. Like PaulSS mentioned, the proximity of transponder and ADS-B antennas to each other is an important issue to some manufacturers. I’m not sure if the general consensus has changed with more field experience, but several of the available units that I checked out had strongly-worded warnings about maintaining minimum distances between the 2. In one case that minimum was 60”! Definitely something to check out and keep in mind.