Com Antenna on Turtledeck?

[Brantel]

I have seen a few pics of RV's with a com antenna on the rear turtledeck.

Question for those that have done this or have knowledge on the subject:

Does it give you better performance on the ground than those mounted underneath?

How different does it perform in the air compaired to bottom mounted ones?

Is there enough ground plane area for it to work well in all directions?

Would you do it again?

I am interested in this because I have seen where several RV's with bottom mounted antennas can't comminicate very far at all while on the ground. I hate picking up clearances in the air and with most spam cans I fly with top mounted antennas, I am able to get clearance from TYS all the way from MOR while on the ground.

 

[Sam Buchanan]

I have seen a few pics of RV's with a com antenna on the rear turtledeck.

Question for those that have done this or have knowledge on the subject:

Does it give you better performance on the ground than those mounted underneath?

How different does it perform in the air compaired to bottom mounted ones?

Is there enough ground plane area for it to work well in all directions?

Would you do it again?

I am interested in this because I have seen where several RV's with bottom mounted antennas can't comminicate very far at all while on the ground. I hate picking up clearances in the air and with most spam cans I fly with top mounted antennas, I am able to get clearance from TYS all the way from MOR while on the ground.

Been flying turtledeck-mounted com antenna since 1999 on my RV-6. In answer to all your questions except the last one....."Don't know since the top-mounted antenna is the only one I've had, but my antenna has worked fine for 875 hrs.".

For your last question, "Yes, unless there was some compelling reason to mount it on the bottom (sliding canopy....can't stand looks of top antenna....??)".

 

[fstringham7a]

RE:Belly Mount Com !!!!

Brian

I am in the final stages of my build of an RV7A which has COM 1 bent whip on the belly. It is in my Garage about 3 miles from the airport.

Everytime I have asked for a radio check I get a response of, Loud and Clear......I must admit that it is probably from aircraft in the air and not from either unicom or an aircraft on the ground.

My Com 2 is an archer style in right wing tip. It isn't connected yet so no word on it yet..............

Frank @ SGU and 1L8 ... RV7A ..... last 992 details of which 900 are FG

 

[Walt]

I mounted a comm ant on top of my 7A after flying many hundreds of hours with only the bottom mounted antennas. I thought I would try a top mount for the 2nd comm and so I replaced the KMD GPS with a comdat GPS/comm antenna, overall the performance is a little better both in the air and on the ground than my belly mounted antenna. Although I'm not really excited about the way it looks, the performance is a little better so I am going to keep it this way.

 

[Rivethead]

Lemons into lemon aid

Brian at some point in building I dropped a tool, I think it was a bucking bar but it could have been that screw driver, later I discovered a nice three corner tear in the skin where it must have landed about three inches behind the main spar under the seating area. It's kind of an involved repair to fix it correctly and I wasn't looking forward to it. After getting the Com antenna I'm going to use and considering all the same questions you are and realizing there are pluses for both locations I decided I would drill out the three corner tear and install it there. Call me lazy if you must but it works for me. Maybe as you go along you'll get a three corner tear of your own. As long as we're talking antenna locations. FrankH from this forum is a local pilot here in Corvallis. Once in a while I get a chance to look his plane over to see what I'm doing the hard way, which as it turns out is just about everything. On my last examination I was noticing his ships antennas and in particular his transponder antenna which is mounted about half way back to the tail feathers. Looking at it, it seemed like a really good location harmonics wise and plan to do the same except that I'm planning for mine to be a bit further back. On a side note, Frank seemed to be familiar with three corner tears also.

 

[az_gila]

Cable lengths and TSOs...

..... On my last examination I was noticing his ships antennas and in particular his transponder antenna which is mounted about half way back to the tail feathers. Looking at it, it seemed like a really good location harmonics wise and plan to do the same except that I'm planning for mine to be a bit further back. On a side note, Frank seemed to be familiar with three corner tears also.

Rivethead,

One small note here.... if you have a Garmin transponder, there are specific maximum cable lengths for different types of co-ax.

The "standard" RG-400 has a maximum approved length of 8.8 ft. - you need RG-304 to go to 12.5 ft. and RG-393 to go to 17 ft. maximum length.

The transponder is one of the few items on our homebuilts that must meet TSO standards, so the installation manual should be followed.

Of course, other transponder makes are different, check the IM...

gil A

 

[Rivethead]

Got ya covered Gil. Thanks for watchin my back though.

 

[Wes Hays]

Brian,
I have a com1 antenna mounted on the turtle deck between the VS and the seam between the forward and rear top skins on a 6A slider, and a com2 mounted on the belly with a bent whip.

Com 1 is a King 155 nav/com - Comant antena on turtle deck
Com 2 is an Apollo GX60 GPS/Com - Comant bent whip on belly under pilot.

Com 1 is the one I normally use and always seem to be able to hear and be heard better on com1, especially on the ground.

In the air, com1 also seems to work better, but that may be because I do not have the radio set right on com2. I have messed with it for quite a while so any of you guys out there who can tell me how to set up a GX60 Comm, I would appreciate any suggestions. It really seems to amplify the voice when I transmit. Is that sidetone? Unfortunately I really don't understand the settings as well as I should. Com2 listens a lot better than it seems to talk. Overall, I would have to say it is not as strong as com1. That being said, a lot of my friends have the bent whip coms on the belly of their planes, and they do not seem to be having any problems. So far I have not heard of any complaints of xmiting or receiving on the ground. They sound fine in the air and seem to have an excellent range.

I would like to put two antennas on the belly of the 7a, but really have enjoyed the good radio with the antenna on the turtledeck.

Sorry for the apples and oranges comparison.

Just my $.02.