Nav/Comm Antennas

Post by **Spike** » Thu Apr 21, 2005 11:26 am

Hmm, what to do what to do. I am quickly coming upon the time to close up the tail surfaces and move onto the wing. One of the questions that has been running around throug my head lately is that of nav/comm antennas.

I am not a fan of the "cat whisker" nav antennas that are found on the top of the VS on most airplanes. There is just something coat hanger'ish about them that I don't like. I know that some people are putting tip antennas in their wings and going that route. Personally, I am a big fan of the blade type comm antennas that you see on the tails of the new 182's. They are attractive and are just about the most effective antenna out there (developed for RNAV) for nav reception. The down fall is that they are way expensive. A two blade set runs around $750. In order to use them I'd also have to fabricate some kind of backing structure and put that in the tail, and align it, before I close up the VS.

Granted you dont get to build many airplanes in your life and there is that feeling of building it the way you want it. On the other hand it will add time and $$$.

What are your thoughts on antennas?

-- John

tshort · Post by **tshort** » Thu Apr 21, 2005 11:41 am

I've been wondering the same thing. I put a couple of extra holes with rubber grommets in the ribs of the VS in case I decide to put something up there.

It seems like most people are getting good results with the wingtip antennas - invisible and no drag. I really haven't seen too many RVs with antennas on top of the VS (altho this is the best place for them...)

I don't know what I'm going to do. What kind of structure are you proposing for the antenna mount in the tail?

Thomas

Post by **Spike** » Thu Apr 21, 2005 11:47 am

I haven't looked too closely yet, but the base of the blades are about 12" x 3 ", maybe a bit thinner. I would at a minimum have to double up the skin. I was thinking of maybe running something like a skin doubler from the rear spar up along the skin where the blade attaches to the front spar, tying it in to both spars. That would help give the skin more torsional strength to withstand any twisting loads that the antennas might apply.

-- John

.... I don't know what I'm going to do. What kind of structure are you proposing for the antenna mount in the tail?

Thomas

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mustang · Post by **mustang** » Fri Apr 22, 2005 12:12 am

Spike,
Keep it clean! Stick it in the wingtip. Cheap and keeps it fast.

Cheers, Pete

captain_john · Post by **captain_john** » Fri Apr 22, 2005 7:19 am

I like the "clean" perspective, too.

What do we have to choose from?

I know the Archer wingtip antennas are made for us, but is anyone else out there?

Ideally, I would like to keep all antennas out of the slipstream. This may not be practical.

I would like GPS (pretty aerodynamically clean already), 2 comms, an ILS/VOR and a transponder. Am I missing anything? Maybe sattelite radio? I suspect that you guys would be doing similar?

That would be 5 or 6 antennas.

What would you use?

CJ

Post by **Spike** » Fri Apr 22, 2005 7:23 am

Yes but how is the reception with those antennas?

-- John

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captain_john · Post by **captain_john** » Fri Apr 22, 2005 7:43 am

Rumor is, they are "good".

Maybe for Comm 2 it would be good?

For Comm 1 something low drag like this?

Comant CI 122

Frequency â€¢ 118-137 MHz

Designed specifically for mounting to the underside of an aircraft providing excellent radiation coverage for air-to-ground communications. Bent configuration makes it ideally suited for helicopters and low wing aircraft.

Low profile and simple. The Cessna logo has to go, though!

CJ

Post by **Spike** » Fri Apr 22, 2005 7:46 am

Good questions John. I want the same thing that you do but I would prefer to have 2 VOR receivers. That is quite a few antennas. Dont forget transponder and marker beacon if you want to fly IFR.

Bob Archer wrote a very good piece of information on his antennas and such and its in our "Document Share". Its a good read if you have the chance. Check it out.

My only concern with the tip antennas is their effectiveness. Has anyone here used them?

-- John

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www.rivetbangers.com - Now integrating web and mail!
www.spikesplace.org/cgi-php/serendipity - Builder's log
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Post by **Spike** » Fri Apr 22, 2005 7:50 am

Actually CJ that is not the Cessna logo, that is the Comant logo. They are the manufacturers of most antennas used on todays GA aircraft, including the kerosene burning ones. Check them out, I have a link to their website on the Resources page.

-- John

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captain_john · Post by **captain_john** » Fri Apr 22, 2005 7:59 am

I wrote transponder, and marker beacons... hmmmm is that another antenna?

Can't I combine it with my VOR/ILS one? Any drawbacks?

Comant IS THE NAME, isn't it? They are the big wigs, aren't they?

I will read the document for a full briefing.

CJ

Post by **Spike** » Fri Apr 22, 2005 9:12 am

Sorry, guess I did not see that ... And from my understanding that is yet another antenna. You may be able to combine them though, I don't know for sure. Maybe someone who know for sure can speak up.

-- John

I wrote transponder, and marker beacons... hmmmm is that another antenna?

Can't I combine it with my VOR/ILS one? Any drawbacks?

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captain_john · Post by **captain_john** » Sat Jul 23, 2005 6:28 pm

Nice!

CJ

l & d lewis · Post by **l & d lewis** » Mon Jul 25, 2005 6:50 pm

Jim Weir at Radio Systems Technology in CA (O17), designes antennas for kit planes. He designed the intigrated antenna for Rutan's Voyger. He'll probably be at OSH. Here's a link to his web site http://www.rst-engr.com/.......... He also used to build kit nav/coms. Antennas can make or break a com installation, its not a place to cut corners. I haven't talked to him in a couple years, but he's really into avionics for homebuilts.....

captain_john · Post by **captain_john** » Fri Jul 29, 2005 8:41 pm

Thanks Larry!

Haven't seen you around here much. Good to see you again!

CJ

l & d lewis · Post by **l & d lewis** » Mon Aug 01, 2005 12:39 pm

Summer here is too short to be indoors building. Empennage is finished, and wings won't be here until late fall. Consentrating on other projects. Closing on a piece of property at Wolf Lake today so we can start building a hangar next summer. I dropped Jim Weir an email the other day, but he hasn't responded, I know he's at OSH, probably hear from him when he returns. He's the guy I'd ask about antennas, he certainly can tell you what you can and can't do with them, and I'm sure he'd make some suggestions................Larry

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