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#1
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Foil antenna and carbon fiber
My Internet search didn't turn up what I was looking for so I came here for
advice. The task at hand is the installation of a foil antenna in a composite canard which would ordinarily be a rather routine task for the plane - a Quickie - but in this case there are some carbon fiber rods at 25% chord that make placement impossible without having the foil either near some of the carbon or metal components. My question: How much does the carbon fiber rods affect the antenna performance compared to a few bits of isolated metal (elevator hinge) and does it make a significant difference if the carbon fiber is PAN or Pitch? |
#3
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A_horizontail_comm antenna?
No, its should not be as I'm sure Roger knows and did not mean a comm antenna. It is either a Marker beacon antenna (horiz stab is the best location due to the MKR antenna length) or a VOR nav antenna. |
#4
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I don't know the specific answer for your situation, but the Glasair
III uses a carbon fiber horizontal stabilizer and they mount the antenna right inside it. up against the carbon fiber lay-up. Thanks, That answers my essential question and I can now position my nav antenna. I'm familure with your G3 structure but didn't know that this was a common place for an antenna. If it works in that application it should work in mine. |
#5
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You're not going to know until you put it in there and measure the
VSWR. But the good news is you can tune the antenna/feed-line after its mounted but before you button things up. The question I'd have about using a foil antenna attatched to a structure that flexes (like a wing spar) is you may someday have a break in the foil after the foil fatigues and then have a flakey antenna the behaves differently in flight than on the ground when you're trying to debug it. cal (BD5ER) wrote in message ... My Internet search didn't turn up what I was looking for so I came here for advice. The task at hand is the installation of a foil antenna in a composite canard which would ordinarily be a rather routine task for the plane - a Quickie - but in this case there are some carbon fiber rods at 25% chord that make placement impossible without having the foil either near some of the carbon or metal components. My question: How much does the carbon fiber rods affect the antenna performance compared to a few bits of isolated metal (elevator hinge) and does it make a significant difference if the carbon fiber is PAN or Pitch? |
#6
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"Jay" wrote in message m... You're not going to know until you put it in there and measure the VSWR. But the good news is you can tune the antenna/feed-line after its mounted but before you button things up. The question I'd have about using a foil antenna attatched to a structure that flexes (like a wing spar) is you may someday have a break in the foil after the foil fatigues and then have a flakey antenna the behaves differently in flight than on the ground when you're trying to debug it. You insert the foil antenna inside a lightweight sheath which is affixed to the inner skin of the horiz stab. Or the spar or whatever. The foil, like that which you can purchase at RS, can flex inside the sheath and not break. |
#7
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On 31 Jul 2003 09:54:33 -0700, (Jay) wrote:
You're not going to know until you put it in there and measure the VSWR. But the good news is you can tune the antenna/feed-line after its mounted but before you button things up. The question I'd have about using a foil antenna attatched to a structure that flexes (like a wing spar) is you may someday have a break in the foil after the foil fatigues and then have a flakey antenna the behaves differently in flight than on the ground when you're trying to debug it. The wing and horizontal stab in the G-III do not flex any where near what you will find in a standard aluminum wing and horizontal stab in something like a Bonanza. The spar in the wing is *massive* and that horizontal stab is rigid. You can stand on one side and not see it flex. I'd not want to do that on my Deb. Roger (BD5ER) wrote in message ... My Internet search didn't turn up what I was looking for so I came here for advice. The task at hand is the installation of a foil antenna in a composite canard which would ordinarily be a rather routine task for the plane - a Quickie - but in this case there are some carbon fiber rods at 25% chord that make placement impossible without having the foil either near some of the carbon or metal components. My question: How much does the carbon fiber rods affect the antenna performance compared to a few bits of isolated metal (elevator hinge) and does it make a significant difference if the carbon fiber is PAN or Pitch? Roger Halstead (K8RI EN73 & ARRL Life Member) www.rogerhalstead.com N833R World's oldest Debonair? (S# CD-2) |
#8
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You can make an antenna out of limp spaghetti and mount it inside a copper
septic tank if you wish -- and everything gets better from there. I cannot believe that an antenna inside of or laid directly on carbon fiber will work. If somebody actually has one WORKING, please post your test results or flight test results. Jim Roger Halstead shared these priceless pearls of wisdom: -I don't know the specific answer for your situation, but the Glasair -III uses a carbon fiber horizontal stabilizer and they mount the -antenna right inside it. up against the carbon fiber lay-up. Jim Weir (A&P/IA, CFI, & other good alphabet soup) VP Eng RST Pres. Cyberchapter EAA Tech. Counselor http://www.rst-engr.com |
#9
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Well, since I've been accused of baiting an argument in these ngs, perhaps now I
am considered a master baiter. Ahem. Instead of answering you directly, I will instead give you general advice. I can't honestly tell enuf about the problem from the description given to point you straight. (BTW, when you post a question during Oshkosh week, be prepared to wait for answers.) The CENTER of the antenna (where the coax connects) is totally numb to metal/carbon. The TIPS of the antenna are the most sensitive. The bigger the metal/carbon the more effect it has. I could make filthy analogies, but I'll let them rest. Keep the TIPS as far away from large expanses of metal/carbon as you can. That's the best advice I can give. Jim cal (BD5ER) shared these priceless pearls of wisdom: -Nav antenna in the lower surface of a canard (tandem wing, big canard). I have -a choice of the tip of one foil strip centered (about 6 inch to either) between -an isolated bolt and fitting in the outer elevator hinge and the carbon fiber -spar, or crossing the spar about 8 inches from the tip. Jim Weir (A&P/IA, CFI, & other good alphabet soup) VP Eng RST Pres. Cyberchapter EAA Tech. Counselor http://www.rst-engr.com |
#10
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(BTW, when you post a question during Oshkosh week, be prepared
to wait for answers.) FULLY understood. I consider any answer from you here a considerable public service on your part. How many other professionals take the time coddle the masses in such a personal and direct way?....... and for free! Thanks |
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