[aerovin]

The GTN-6XX install manual states that for best performance, a second comm antenna should be mounted at least six feet from the GTN comm antenna. For those with GTN-650 installations and a second comm also installed, how are your comm antennas positioned?

The only practical surface to mount a conventional comm antenna on the RV-8 is the fuselage belly and there is not enough real estate unless the second comm antenna is mounted well aft, which probably won't provide sufficient ground clearance. From my photo search, it would appear most dual comm antennas are mounted side by side just aft of the main spar on the fuselage belly, which works out to about two feet of separation. I am not considering a wing-tip comm antenna installation. Anyone out there with real life experience with the GTN-650?

 

[jthocker]

I have the antennas mounted exactly as stated. GTN 650 and PAR 100 EX, both work just fine. Lots of IFR with long distance communications with ATC and teammates traveling in opposite directions, 200 miles sometimes!

 

[Alan Carroll]

The only practical surface to mount a conventional comm antenna on the RV-8 is the fuselage belly and there is not enough real estate unless the second comm antenna is mounted well aft, which probably won't provide sufficient ground clearance.

Actually there's also plenty of flat real estate under the wings. I tried mounting an second antenna on one of the inboard access covers, which I reinforced with a doubler that has one edge bent up as a stiffener. Seems to be doing just fine there about 100 hours later. An added benefit is that the antenna doesn't get coated with exhaust soot.

 

[flyingbeaver26]

Slightly off topic

Sorry for the off topic response here. I also installed both com antennas on the belly of my -8. I'm planning on installing a GTN 650 as well. I wanted to be IFR capable. So I was planning on installing a second radio as well. Since the GTN 650 uses two comm antennas, can it suffice the IFR requirement and act as two independent radios? or to be legal, do I need to install a 3rd comm antenna and a 2nd radio?

Brad
-8 wiring

 

[ColoRv]

Sorry for the off topic response here. I also installed both com antennas on the belly of my -8. I'm planning on installing a GTN 650 as well. I wanted to be IFR capable. So I was planning on installing a second radio as well. Since the GTN 650 uses two comm antennas, can it suffice the IFR requirement and act as two independent radios? or to be legal, do I need to install a 3rd comm antenna and a 2nd radio?

Brad
-8 wiring

Two comm antennas? The GTN650 has a comm, a VOR and a GPS. The VOR I put in the wingtip, which is less than ideal but hey, it's VOR...who uses that anymore? (kidding) The GPS is under the cowl on a shelf and the Comm's from the GTN and the PAR are on the belly behind the spar and as far outboard as I dare. The VOR could be put in the tail with whiskers, but it wouldn't be a bent whip like the comms.

All of that said with the caveat that I may have done it wrong....I'm not flying yet. Stein did give it a thumbs up....but then you know how that guy is...he just wants my last dollar!

And he will get it soon....

 

[Brantel]

Sorry for the off topic response here. I also installed both com antennas on the belly of my -8. I'm planning on installing a GTN 650 as well. I wanted to be IFR capable. So I was planning on installing a second radio as well. Since the GTN 650 uses two comm antennas, can it suffice the IFR requirement and act as two independent radios? or to be legal, do I need to install a 3rd comm antenna and a 2nd radio?

Brad
-8 wiring

It's only got one COM antenna....

 

[jthocker]

Two comm antennas? The GTN650 has a comm, a VOR and a GPS. The VOR I put in the wingtip, which is less than ideal but hey, it's VOR...who uses that anymore? (kidding) The GPS is under the cowl on a shelf and the Comm's from the GTN and the PAR are on the belly behind the spar and as far outboard as I dare. The VOR could be put in the tail with whiskers, but it wouldn't be a bent whip like the comms.

All of that said with the caveat that I may have done it wrong....I'm not flying yet. Stein did give it a thumbs up....but then you know how that guy is...he just wants my last dollar!

And he will get it soon....

I have same equipment, same antenna placements, everything works great!

 

[db8]

Same same

I too have the same set-up with the 650. Two com antennas just aft of the spar on the belly as wide as possible. Have had zero issues and would do it again. I also have the GPS antenna under the fiberglass cowl on a shelf.

From what I understand, it's not critical to have the spacing on these. It is critical to have it on the ADS-B between the transponder and ADS-B Out antenna (I think five feet). That's because you can fry one (or both) of the units.