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jon
12-11-2004, 08:17 AM
Trying to pic a location for a com. antenna on a Smith cub.
Was thinking of installing it just behind the skylight and fab a base for it
to mount on. Any ideas on antennas? and ground plane?
Thanks, Jon

Steve Pierce
12-11-2004, 08:31 AM
I use the wing root fairing as far forward as possible. I brake a "U" channel to mount underneath. You end up with a ground plane through the wing and fuselage.

bushmaster
12-11-2004, 09:11 AM
why far forward. Mine is just aft of center skylight channel

irishfield
12-11-2004, 12:12 PM
Ditto to Steve's reply. Why put a hole thru the top of your fuselage when you've got those nice ground plane alum strips on each side between fus and wing. I put my Comm antenna on one side and GPS puck on the other. Just pick a spot that is clear of fuel lines/sight gauge etc and go with the area with the most room to work in and avoid possible RF interference from strobe/nav wires etc

Wayne

diggler
12-11-2004, 03:59 PM
delete

cubunltd
12-11-2004, 05:21 PM
Ditto to Steve's reply also. This isn't rocket science. put it on the fairing where ever it looks good.

Steve Pierce
12-11-2004, 06:11 PM
I put it close to the front cause it is closer to structure and fastened down better, clear of the fuel gauge and easier to get to when I need to work on it. I agree with Diggler on the hanger clearance but still prefer them at the top.

CrossedControls
12-12-2004, 08:44 AM
Another reason is shorter cable runs, the shorter the cable the lower the loss. If you are using long runs use the best low loss cable, and as few connectors as possible (don't join two cables to make a longer one).

Pete

SuperCub MD
12-12-2004, 11:34 PM
I put them aft also that way you have more clearance in a low hanger.

Aft for hanger clearance, and on the wing root fairing, not the tank cover or fabric. If you ever want to change or remove antennas, making a new wing root fairing is cheaper and easier.

narov
12-13-2004, 09:28 AM
Or try this location 8)

http://www.ellipsedirect.com/photo-cessna150.jpg

Wingie
12-13-2004, 02:19 PM
I always liked the lower placement on the top wing root fairing, for clearance coming into the hanger. Just enough aft of the rear spar to provide clearance for the cable connection.

I've been waiting for someone else to bring it up, but I don't see it happening. On my last project (certificated Cub), I installed a VHF-5I (Advanced Aircraft Electronics, Inc) fiberglass substrate comm antenna inside the fuselage (owner wanted NO antennas on the outside, he $ettled for the tiny 20 dollar whip for the xpdr. No nav due to GPS handheld bracket mounted on the panel), and have seen more than acceptable performance "down here" in the lower 48. Does anybody have any "high performance" experience with these? As in LONG range transmissions, send/receive? As I say, having excellant results "locally", but haven't had the opportunity to "reach out and touch someone". It presented some interesting head-scratching moments getting it installed inside the fuselage and getting it to remain "within 45 degrees of vertical", and had to settle for fudging it a few degrees when in the tailwheel is on the ground. Being a bit out of recommended installation orientation doesn't seem to effect ground communications in any way, even from all the way across the BEEG airport. Can't see ANY differance one way or the other when in flight from the high dollar composite antenna that used to be hooked to this same B-K KY-97. ATC says "nice and crisp. Loud and clear." when asked "how me"? Never more than 40 miles away around here, however (lemme up. its not MY fault!)

cubunltd
12-13-2004, 04:52 PM
I was going to install one of those in my latest PA18, but because of my extended baggage compartment, had no room. Going to install it in a J3 that I'm finishing up. It'll be used for a handheld.

sjohnson
03-12-2009, 02:34 PM
I installed an Advanced Aircraft Antennas VHF 5T in the vertical stabilizer, so that about half of it extends above the fuselage in level flight. No physical interference with the extended baggage. Seems to work ok after 5 hours. When it warms up, I'll measure the antenna pattern and report back.

Steve

skywagon8a
03-12-2009, 03:39 PM
I have not tried this myself yet but, I had a fellow who worked for a avionics manufacturer tell me that the antenna could be mounted inside the fuselage on any tube and fabric airplane. Just mount the antenna on a sheet of aluminum for a ground plane to the lower tubing. Ground the aluminum to the frame. That's it. Can't see it and it won't hit the hangar.

sjohnson
03-12-2009, 04:21 PM
The AAE antenna is a dipole and does not need a ground plane. This also helps isolate it from the tubing, so presumably it will perform better than a monopole (the typical aircraft whip antenna).

I've known some guys that mounted a whip antenna to a ground plane in the fuselage. It functions, but signal strength is significantly attenuated forward by either the baggage compartment or the firewall. I mounted my ELT antenna this way, assuming that a little degradation would be better than snapping the antenna off in a crash. I think the Aviat Husky implements this as well.

Steve

AIRWOLF
03-12-2009, 06:57 PM
I installed an AAE VHF 5T in my vertical stabilizer last summer and it works great. I was a little worried about the silver dope blocking the signal but it doesn't seem to.

McAlpine
03-12-2009, 07:11 PM
Also, if lifting eyes are on or going to be on in the future might want to move them back a little bit from the front.

Ruidoso Ron
03-12-2009, 07:14 PM
You also should never mount a second vertical antenna (comm 2, or whatever) too close to the comm antenna. They will each attenuate the signal from each other, and reduce the range.

sjohnson
06-01-2009, 09:36 PM
I never got a chance to measure the antenna pattern of the AAE antenna, but after 30 flight hours, it's working great. Range is good and no nulls have shown up. I'm really pleased with it.
Steve

Gordon Misch
06-01-2009, 09:53 PM
You also should never mount a second vertical antenna (comm 2, or whatever) too close to the comm antenna. They will each attenuate the signal from each other, and reduce the range.

Ron, how close is 'too close'? Serious question - really! :)

Ruidoso Ron
06-05-2009, 05:36 PM
Gordon,
Sorry I am so slow responding. I have been out of town for several days. I am not sure what the answer is, but I have always thought that a minimum of 18" would do. Personally, I have always planned to have them on opposite wing root fairings.

5 Rivers
06-07-2009, 12:45 AM
I installed an Advanced Aircraft Antennas VHF 5T in the vertical stabilizer, so that about half of it extends above the fuselage in level flight. No physical interference with the extended baggage. Seems to work ok after 5 hours. When it warms up, I'll measure the antenna pattern and report back.

Steve



Steve do you have any pics of your AAE installation?

Randy

sjohnson
06-07-2009, 10:58 PM
Here's a couple of attempts. I'll hunt around for more photos. The plane is covered now.
Here's the general location:
http://www.supercub.org/photopost/data/500/Comm_antenna_installation.jpg

Here's the actual installation:
http://www.supercub.org/photopost/data/500/Antenna_placement_070607_full.jpg
The black strip is the antenna. The upper part will fit between the fabric and the vert. stabilizer frame members. The lower part is supported by a wood 1x2. Roughly the midpoint of the wood member is attached to the fuselage with an Adel clamp. The bottom is supported by a short fore-aft aluminum angle member, which is attached with two Adel clamps.

The BNC connector points to the rear, which allows the connector to be accessed after the plane is covered. On this plane, the last fuselage bay has a removable panel on the bottom. This was a test fitting - the final installation may be slightly different, but this illustrates the general idea.

Steve

5 Rivers
06-08-2009, 12:33 AM
Steve,
Thanks for the pics and info.
I'm looking at a few options as well and sure like the idea of a internal mounted antenna.
Is the weight about the same as the standard external antenna on most cubs?

Randy

sjohnson
06-08-2009, 10:52 AM
I haven't compared the installed weight, but I would expect that the difference would be minimal. The antenna itself weights only 2.3 oz.

Note that the coax will be longer to the tail than to the wing root. Use good quality coax (e.g. RG400, low loss RG58) to avoid losing a lot of power in the coax. The coax is probably the heaviest element in either the AAE or whip antenna installation.

Steve