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Antenna Holes in Lower Tail - VOR or Cover?

JDA_BTR

Well Known Member
When you use a GTX-45R transponder you only need one antenna for ADSB In/Out, and it should be run to the antenna at the right baggage area to keep the length of run in spec.

So the standard kit has a cable running all the way aft to the tailcone with holes for an antenna there. I think it was intended to be a UAT receive antenna.

I've been pondering putting a VOR antenna there but the hole spacing for the 2-hole VOR puck is slightly different than the spacing in place for a UAT antenna. I also have the gear to put the VOR antenna in the wingtip. The wingtip install is cleaner.

1. Any opinions about getting the 4-hole VOR antenna and putting it under the tail? Anybody done this on a 14A and have a pic?

2. If I abandon the aft holes what is the best way to cover it up? Could just screw up a thin cover to a thin backing plate on the inside. Or more elaborately rivet a patch in. Any opinions about that?
 
I fabricated a cover. Plan at this point is to pro seal in place on the interior and smooth at paint will body filler.

However, I think this might be a good place for a camera mount and have delayed any further work on this until just before final horizontal / vertical install. I am thinking of re-working the patch with thicker material and calling it a doubler. Use a piece of skin thickness in that area to rivet to the doubler to fill the large round antenna hole, then place a rivnut in the middle to accept the camera mount. Smooth and fill the rest at paint. Just my current idea. Not even sure if this would work. My r/d to continue.
 
When you use a GTX-45R transponder you only need one antenna for ADSB In/Out, and it should be run to the antenna at the right baggage area to keep the length of run in spec.

So the standard kit has a cable running all the way aft to the tailcone with holes for an antenna there. I think it was intended to be a UAT receive antenna.

I've been pondering putting a VOR antenna there but the hole spacing for the 2-hole VOR puck is slightly different than the spacing in place for a UAT antenna. I also have the gear to put the VOR antenna in the wingtip. The wingtip install is cleaner.

1. Any opinions about getting the 4-hole VOR antenna and putting it under the tail? Anybody done this on a 14A and have a pic?

2. If I abandon the aft holes what is the best way to cover it up? Could just screw up a thin cover to a thin backing plate on the inside. Or more elaborately rivet a patch in. Any opinions about that?

Since coax already in place and transponder/adsb antenna fits using tail location for that. I’ll probably put patch of some sort over right mid fuse location. Talked with Stein about cable length - he thinks it will be fine. I decided on Archer VOR antenna in right wingtip
 
I'm running the GTX-45R and am using the coax to the rear as per plans. I had the transponder check done prior to 1st flight and I asked the avionics guy who was doing the testing about the coax run and he said it was fine and the transponder test came out fine. He is also a Garmin dealer and is very familiar with G3X install procedures.

I was not happy clumping the 2 comm antennas plus the transponder antenna so close together unless absolutely necessary.
 
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I'm running the GTX-45R and am using the coax to the rear as per plans. I had the transponder check done prior to 1st flight and I asked the avionics guy who was doing the testing about the coax run and he said it was fine and the transponder test came out fine. He is also a Garmin dealer and is very familiar with G3X install procedures.

I was not happy clumping the 2 comm antennas plus the transponder antenna so close together unless absolutely necessary.

this sort of changes things then. Guess I might be re-running that cable.
 
I put a small blade ADSB antenna under the baggage compartment, honoring the cable length specified in the G3X plans. I considered several options for the tail cone holes and finally just put a short Transponder antenna there. It is not wired to anything, but fills the center hole and looks ?normal.? :rolleyes:
 
I posted a similar thread here after drilling the holes in my F-01479 Aft Bottom Skin. I considered every possible thing to put in that location, including DME and stormscope antennas and a camera mount. My conclusion was to order a new F-01479, in which I dimpled and filled the holes with rivets. The original F-01479 sits in my "pile of shame" in the corner of the airplane factory. I do not have that coax in my tailcone. It would be trivial to run a cord and drill out the rivets if I or my heirs decide to put something there.
 
I considered putting my transponder antenna back there but got some garmin advice that it was too long a run. The little post antenna isnt a bad idea even if it just fills the hole.

In hindsight I would have not made the hole but that was 4 years ago and little did I know....

I?m a ham radio operator maybe a 2m antenna.
 
COM antenna under tail

Any reason not to put a bent-whip COM antenna back in those F-01479 holes using the existing coax? It would serve double duty as tail strike early warning system. ;)
 
Any reason not to put a bent-whip COM antenna back in those F-01479 holes using the existing coax? It would serve double duty as tail strike early warning system. ;)

Van's provides two locations for COM antennas just in front of the spar carry-through structure. Easy to run cable from this location, and doublers already in place, holes drilled to fit the antenna (Delta Pop has the right spacing for the existing holes). I'm very happy with the antennas and location.

For the aft-most antenna location, I covered the holes: I made two small aluminum plates: one for the inside with nutplates that were centered on the two small holes, the other with corresponding holes for screws to "sandwich" the plates over the skin. Easy to remove in the future for another antenna if needed.
 
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Van's provides two locations for COM antennas just in front of the spar carry-through structure.

Right, not debating the amazingly beautiful perfection of that placement, but rather wondering what to do with the extra hole now that GTX 45R all but obsoleted it.

One idea is to reuse that tail location and the long cable for COM, one of the forward locations with short cable for xponder, and the middle-fuse one for, say, a wideband cell phone signal booster from Delta Pop.

COM doesn't care much about the long cable as the loss at 120 MHz is tiny, but unsure what the odd cylindrical ground plane would do for radiation pattern and SWR.

Then there's the aesthetics of it. "My airplane is a convertible, that's a tail skid for rough unimproved strips."
 
Right, not debating the amazingly beautiful perfection of that placement, but rather wondering what to do with the extra hole now that GTX 45R all but obsoleted it.

One idea is to reuse that tail location and the long cable for COM, one of the forward locations with short cable for xponder, and the middle-fuse one for, say, a wideband cell phone signal booster from Delta Pop.

COM doesn't care much about the long cable as the loss at 120 MHz is tiny, but unsure what the odd cylindrical ground plane would do for radiation pattern and SWR.

Then there's the aesthetics of it. "My airplane is a convertible, that's a tail skid for rough unimproved strips."



I have produced a number of 2.4 GHz WIFI antennas that will bolt in that location, several are experimenting with airborne WIFI.
 
Im thinking of pop riveting my data plate over those holes. Anybody know if the bottom of tail is a legit location for the data plate?
 
Im thinking of pop riveting my data plate over those holes. Anybody know if the bottom of tail is a legit location for the data plate?

Interesting question. This is from EAA website:

"[T]he aircraft identification plate must be secured to the aircraft fuselage exterior so that it is legible to a person on the ground, and must be either adjacent to and aft of the rearmost entrance door or on the fuselage surface near the tail surfaces.

Note that the regulation specifically requires the data plate to be on the exterior of the aircraft. It cannot be mounted on an interior surface, even if it is visible from the outside. The regulation also stipulates that the date plate should not be attached in such a manner that it will not likely be defaced or removed during normal service, or lost or destroyed in an accident. Thus, the data plate should not be placed on an inspection cover or access door, or on any part that is commonly removed for maintenance or inspection. It should be attached to the fuselage itself"
 
I'm using mine for a curtesy light. I already had a spare pair of wires going back there so why not a lil LED to help with the tie down and preflighting in the dark.
 
That really is the best idea yet. I don't have a spare wire going all the way back there but I'm not too proud to hijack the RG400 for a power lead.
 
When you use a GTX-45R transponder you only need one antenna for ADSB In/Out, and it should be run to the antenna at the right baggage area to keep the length of run in spec.....

Which spec are you referring to? I'm looking at the GTX-45R ADSB Transponder Installation Manual and the only wiring specs that I'm finding are on page 3-7 and 3-8, and the only length requirement that I see is that there has to be a minimum of 3' of cable between the GTX-45R and the antenna.

Thanks!
 
I remember someone at Garmin told me the distance allowed for the adsb antenna changed from the hole in the tailcone to the position under the baggage compartment. I suggest speaking with someone from Garmin, perhaps the G3X guys can provide the best contact.
 
I remember someone at Garmin told me the distance allowed for the adsb antenna changed from the hole in the tailcone to the position under the baggage compartment. I suggest speaking with someone from Garmin, perhaps the G3X guys can provide the best contact.

I can't see why there would be a maximum distance requirement if you're using a cable of adequate size and you meet the requirements set forth in the installation document, but I'll certainly check with Stein and / or Garmin. Screenshot of the installation doc requirements is below.

ADSB%20antenna%20wiring%20requirements.jpg


Thanks!
 
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I can't see why there would be a maximum distance requirement if you're using a cable of adequate size ...

Thanks!

I think you?re thinking of power cables at low frequencies or DC, and ohmic losses. At a GHz, it hardly matters how thick the wires are - nearly all the current is in a thin layer at the surface of the conductor. And all practical foam dielectrics absorb energy at these frequencies. If the cable is too long, the losses can be too high...
 
I think you?re thinking of power cables at low frequencies or DC, and ohmic losses. At a GHz, it hardly matters how thick the wires are - nearly all the current is in a thin layer at the surface of the conductor. And all practical foam dielectrics absorb energy at these frequencies. If the cable is too long, the losses can be too high...
Thanks Bob. Are you aware of any cable length limitations for the ADSB antenna cable run? I can't seem to find any in Garmin's installation instructions.

Thanks!
 
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