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Show me your antennas (esp. VOR and GPS)

iamtheari

Well Known Member
My RV-14 fuselage kit will be here in the next couple of weeks, and my tail cone is taking shape. I figure that now is an appropriate time to think about adding doublers for antennas. The kit already seems to accommodate two comm antennas on the belly, a transponder/ADS-B antenna on the bottom of the tail, and the ELT antenna inside the baggage area.

I am planning to have a GTN 650, a GMA 245R, and a G3X Touch with SiriusXM. My understanding is that I will need the following antennas in addition to those that the kit provides for, as listed above:

1. VOR/LOC/GS
2. GPS for GTN 650 (GA 35)
3. GPS/XM for G3X Touch (GA 57X)

I'm not the first one doing this, by any stretch of the imagination. So, please show me where you mounted these antennas on your RV. Thanks!
 
I have not yet mounted my antennas, but I have them and I am about at that point. I will mount the GPS/XM antennas on top immediately behind the baggage bulkhead. I will use an Archer Nav antenna, and will mount it in the right wingtip. These are common locations for these antennas, but you have plenty of time to consider alternatives.
 
The 2 comm antenna mounts on the belly have doublers in the kit. The fwd and rear transponder/ads-b holes will need doublers fabricated as will the top mount location for the GA35. I am using an Archer wing tip nav antenna in the right tip - lots of documentation around on mounting it there. I have an extra GPS antenna on the front dash for a Garmin G5.

If you really want to, you can install the transponder doublers as you build the fuselage but in my case I only need a single antenna for transponder / ads-b so the fwd hole will have a plate over the holes. The top deck mounted GA35 you can reach any time but doing it before attaching the tail cone and fuselage will save a little bit of work later.
 
I did not realize that there was a transponder antenna location designed into the plans other than the UAT located in the tail cone.
 
I did not realize that there was a transponder antenna location designed into the plans other than the UAT located in the tail cone.

There is one, mid fuselage. Look for three small holes, little off center and away from the bottom ribs.
 
Transponder/ADS-B out under the baggage area because of cable run length as noted above. ADS-B in in the tailcone.

This is how mine is set up.
 
If you're using the Garmin remote xpdr 45R or the 345 no seperate ADS-B/UAT in antenna is required.
 
Since the holes for a transponder antenna are already drilled below the baggage compartment and not required for ADSB, I will install a dummy transponder antenna. Seems better than installing a plate.
 
If you're using the Garmin remote xpdr 45R or the 345 no seperate ADS-B/UAT in antenna is required.

This is great to hear. I'm thinking of mounting VOR/NAV antenna in the tailcone and ADS-B / transponder mid-fuse.
 
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I now feel dumb for having already drilled the holes for the UAT antenna in the tail skin. I thought it was intended for the transmitter side of that whole affair. The supplied cord is 15 feet long, give or take a few inches. I will have to debate covering it up or finding a VOR antenna that will work in that location.
 
I now feel dumb for having already drilled the holes for the UAT antenna in the tail skin. I thought it was intended for the transmitter side of that whole affair. The supplied cord is 15 feet long, give or take a few inches. I will have to debate covering it up or finding a VOR antenna that will work in that location.

I've researched this and many recommend "cat whisker" style antenna in this location. I like that option better than on the V-stab. Archer in wingtip is an option as well.
 
I've researched this and many recommend "cat whisker" style antenna in this location. I like that option better than on the V-stab. Archer in wingtip is an option as well.
The wingtip option seems like less drag, and any difference in reception is justifiable since I won?t use the nav radio much (but do want it so I can always fly an approach or navigate in case of GPS outage).

But the useless holes in the fuselage will bug me. :)
 
My RV-14 fuselage kit will be here in the next couple of weeks, and my tail cone is taking shape. I figure that now is an appropriate time to think about adding doublers for antennas. The kit already seems to accommodate two comm antennas on the belly, a transponder/ADS-B antenna on the bottom of the tail, and the ELT antenna inside the baggage area.

I am planning to have a GTN 650, a GMA 245R, and a G3X Touch with SiriusXM. My understanding is that I will need the following antennas in addition to those that the kit provides for, as listed above:

1. VOR/LOC/GS
2. GPS for GTN 650 (GA 35)
3. GPS/XM for G3X Touch (GA 57X)

I'm not the first one doing this, by any stretch of the imagination. So, please show me where you mounted these antennas on your RV. Thanks!

My avionics : G3X Touch (x2) / GTN650 / GTX35R / GTR 20R / G5 ...
The antennas : GTN650: GA35 / GTR Com2 + GTN Com1 : 2 Comant Ci 122 (belly) / VOR : Bob Archer (wing tip) / 2 GA 26C for GDU and G5 (under upper cowl).
 
The GTX 45R manual doesn?t seem to specify a maximum cable length, so I should be okay to use the rear location.

Not a great idea unless your xpdr is in the back, you still have to pass a xpdr cert which requires 125w minimum output at the antenna. Typically 1.5db cable loss is the spec for xpdrs which is about 6' for RG400. Make it longer at your own risk.
 
I guess to be safe it makes the most sense to put the transponder antenna in the location under the baggage compartment, as appears to be shown in part F-01484 on page 29-02.

I am also leaning toward the Archer VOR antenna in the wingtip, for minimum drag. There aren't any good VOR antennas that would cover up my drilled part anyhow.

So now the question is what to do about the holes I drilled in F-01479 and the coax cable that I pulled back to that location. Any ideas from the much wiser, more experienced builders out there?
 
huge bummer

I did the same thing and drilled the hole + ran the UAT cable that came with the tailcone. Big mistake to cut a huge hole that I now have to figure out what to do with. The UAT cable and hole should be removed from the plans now that the 45Ris becoming more common. Interested to hear solutions, I too am tempted to run the antenna to that location anyways. Hopefully the forward hole isn't drilled out in the QB fuse.
 
The GTX 45R manual doesn?t seem to specify a maximum cable length, so I should be okay to use the rear location.
I asked my avionics shop about this limitation and he did not agree. He said they have put many transponder in planes such as kingair with longer run and has had no issues.

I have also drilled the spot in the tail cone only to find out that I may not have needed it. So I guess a bit more research is needed to see if I should put it in the baggage area or in the tail.
 
I did the same thing and drilled the hole + ran the UAT cable that came with the tailcone. Big mistake to cut a huge hole that I now have to figure out what to do with. The UAT cable and hole should be removed from the plans now that the 45Ris becoming more common. Interested to hear solutions, I too am tempted to run the antenna to that location anyways. Hopefully the forward hole isn't drilled out in the QB fuse.

My -14A fuse kit came with small covers designed to go over the openings where steps are installed for those who are building the tail dragger option - those openings are much larger than the opening in the tailcone you're talking about.. It shouldn't be too hard to fabricate a cover of some sort to rivet over the opening (or use screws for possible future use of this hole for antenna, camera, whatever). It's in a very inconspicuous location fortunately.
 
The GTX 45R manual doesn?t seem to specify a maximum cable length, so I should be okay to use the rear location.

Hello iamtheari,

Sorry that the new GTX 35R/45R manual doesn't specify the maximum cable length. We will need to get that added.

The GTX 345 manual does specify the maximum loss between the transponder and antenna to be 2.0 dB.

RG 400 coax is ~0.185 dB per ft loss
BNC connectors are ~0.2 dB each (0.4 dB total)

The maximum length of the RG 400 cable should be (2.0 - 0.4 dB)/0.185 dB/ft or 8.6 ft. The minimum length is 3 ft.

We installed the GTX 45R in the tail of our RV-7A with the minimum length cable to the bottom mounted antenna nearby.

Thanks,
Steve
 
But the useless holes in the fuselage will bug me. :)

I used these to plug fuel tank vent tube holes in the fwd lower fuselage on my -7A and the un-used pitot static hole in the left wing.

You can pick them up at one of the big box home improvement stores. None have come out in over a year.
 
Hello iamtheari,

Sorry that the new GTX 35R/45R manual doesn't specify the maximum cable length. We will need to get that added.

The GTX 345 manual does specify the maximum loss between the transponder and antenna to be 2.0 dB.

RG 400 coax is ~0.185 dB per ft loss
BNC connectors are ~0.2 dB each (0.4 dB total)

The maximum length of the RG 400 cable should be (2.0 - 0.4 dB)/0.185 dB/ft or 8.6 ft. The minimum length is 3 ft.

We installed the GTX 45R in the tail of our RV-7A with the minimum length cable to the bottom mounted antenna nearby.

Thanks,
Steve
Steve: Thank you. I don't suppose you have any cool tips for how to use the holes I drilled in the skin or the 15-foot coax running back to the tail.
 
I decided to pull the coax out (11 oz of weight in the tail) and order a replacement tail skin. $24 vs my OCD, OCD won. I also ordered the flap position kit and double sided tape so I don?t have to use pro seal on the elevator trailing edges if I don?t feel like it. (Although the rudder turned out nearly perfect using pro seal and results are all that matter.)
 
It has been driving me crazy as well...

I think I am going to fabricate both a flat piece of aluminum with nutplates that can be screwed in to completely cover the hole, and a second piece that has a gopro mount protruding through the 1/2 inch hole I drilled in my airplane. That way I can either run with the cover or have a camera with a great view.

This means dimpling the two #12 holes for screws (using a pop rivet die?)
 
It is a pretty nice drain hole back there huh? Wouldn't be a bad option for a VOR antenna in a trigear except for the drag. Not sure which one is plug/play there.

I was going to see how it went with my 45R with the transponder antenna in the tail but now I guess not....
 
Archer internal VOR wingtip antenna is the only option! Installed per the instructions it works very well. Cats whiskers are ugly and draggy!
Pete
 
Archer internal VOR wingtip antenna is the only option! Installed per the instructions it works very well. Cats whiskers are ugly and draggy!
Pete
Which model of Archer antenna did you use? I see they have a few different styles and I can't tell the difference from a distance.
 
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