comm antennae location--wing or canopy area?

alpinelakespilot2000 · #1 05-08-2005, 10:16 PM

Picking up my wings this week or first part of next...

I plan on running one conduit down each wing for lights/strobes/autopilot, etc. but have heard that it's not good practice to run antennae in the same conduit with strobes due to potential interference. That said, what are the options for my comm. antennae's location? (I have no desire to put in a nav antennae, so that's not an issue.) I've heard some people recommend putting the comm ant. up around--and inside--the cannopy/fuse area with no need for any antennae in the wing at all. That would be my preferred method rather than 2 conduits down one or more wings.

Any thoughts about what location of comm. antennae works best and whether there is any reason to run more than one conduit down each wing?

Aside from conduit, proseal, and Duckworks leading edge light kits, is there anything I should pick up from Van's while I'm there picking up my wings?

Thanks for your thoughts,

Steve

Rick6a · #2 05-09-2005, 11:04 AM

Is there any reason you have not considered mounting a bent whip Comm antenna on the belly?

gmcjetpilot · #3 05-09-2005, 11:29 AM

Your wing tip antenna will never be as good as a simple bent whip on the belly.

The drag created by a belly bent whip is in the ball-park of 1/3rd to a 1/2 mph at 205mph IAS, max.

A few say their wing tip comm. antennas works great, but great might mean talking to the tower 10 miles away, not the remote flight service or ATC station 80 miles away. After the hassle of installing it they want it to work.

Many more have tried the wing tip comm. antenna and where very unhappy, ended up adding the belly antenna anyway.

A belly bent whip installation: shorter coax run, lighter, easier to install and little affect on eye appeal.

A powerful long-range comm. is an important safety item. Tower, ATC, flight service and other aircraft need you to transmit a strong signal for safety, unless you are just going to fly local 10 miles from the field.

Last: WHY? For speed? Looks? I race my RV on occasion and have a whip. I can remove my belly antenna in 1 minute, temporary speed tape the hole and use a handheld if I want. Since I only race once year this is a good compromise. Speed difference with and without antenna is Nil for most, except the most hard core racer. Pilot technique makes more difference in a race than antenna drag from one comm.

What about everyday flying? If you cruise at 170 MPH IAS (190 TAS) you might have a 0.2 MPH drag penalty or 0.002 of the total drag. Assuming a 180HP engine and 0.80 prop efficency that is about 0.3 HP. On a cross-country flight of 4 hours, assuming your at cruise speed the whole time, we are talking about 15 seconds difference in flight time or 4.2 Oz of fuel. May be a gallon of gas a year is needed to drag the antenna around. Is it worth it to have to repeat yourself or hear "Say again" about 100 times a year?

If you are flying an "A" model with steps, a wing tip antenna is like saving a grain of sand in a sieve. Ditch the wing tip antenna. As far as the canopy antenna , they work better with the tip up, but you will have limited performace, especially with a slider and the roll bar nearby.

Regards George

PS:If you must have a VOR/LOC antenna, the wing tip ant. works OK, since it is receiving not transmitting. You will have reduced range and blind spots, but this may be acceptable. With GPS you are likely to only use the VOR/LOC in the terminal area (ie close to the transmitter). Therefore the wing tip antenna for the VOR is OK, but the same things apply still apply to the VOR as the comm. antenna. My old RV-4 VOR/LOC/GS whiskers were under the Horz stab. Out of the way and worked well. Again I could remove it with two screws. I would wrap a .025 saftey wire around the coax connector and speed tape over the hole and a little length of the safety wire. The wire was to keep from loosing the coax in the fueslage, which would mean crawling in the back.

alpinelakespilot2000 · #4 05-09-2005, 01:02 PM

Thanks for the replies. Actually belly mount is where I've assumed it will go, although somewhere I heard good things about wing-tip antennae or somewhere up around the canopy roll bar, or something. Just checking to see if anyone knows where/why I may have heard that. Maybe it wasn't from a very good source, who knows.

Steve

robertahegy · #5 05-09-2005, 05:28 PM

I used the bent whip belly mount and also located a shark fin xponder antenna there as well. Mine are located on the skin under the bagage compt and doing very well. Good reception and transmission.

Roberta

alpinelakespilot2000 · #6 05-09-2005, 06:22 PM

Thanks Roberta. More ammunition for the tried and true location. It's definitely looking like one strand of conduit down the wings will suffice.

Steve

hngrflyr · #7 05-09-2005, 07:01 PM

The comm antenna on our RV-6 is on the back of the fuselage just behind the canopy. While climbing from a runway, and trying to communicate with a ground station that was dead ahead, 25 miles away, the antenna's ground plane was between the antenna and the ground station. Communication was not possible till I put the nose down. Somewhere on the bottom of the plane is a better location.

Bob S.

alpinelakespilot2000 · #8 05-09-2005, 08:02 PM

Was going through Van's catalog and found that they were the source of my info. on the inside canopy comm antennas:

Quoting from p. 52 of the 2005 catalog:
"Similar to those in our prototypes. The antennas are mounted on the inside of the canopy.... Radio performance is only slightly less than external antennas (depending on individual installation, it may be difficult to detect a difference) but many pilots will accept this for the advantages of less drag and lower price."

While I'm not concerned about the drag of an external attenna, I am interested in the cheap ($7.00) price if, in fact, the performance is only "slightly less than external."

Has anyone used these and have first hand experience regarding reception?

Steve