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Old 09-26-2023, 06:17 AM
GEM930 GEM930 is offline
Join Date: Aug 2007
Location: Chico (KCIC) , CA
Posts: 271
Default Archer VOR antenna modified for com?

Years ago I purchased and installed an Archer VOR antenna in my wing tip for my 430 install. That install never happened and now Iím installing a GNC 355 and have no need for the VOR antenna. The 355 will be connected to my typical external com antenna and has a second frequency monitoring feature, so while I donít NEED a com 2, I have a MGL V6 as com 2/ backup/ intercom. I need to keep it mostly for the intercom. Iím not excited about adding another external antenna especially for a radio that will not get much use above monitoring 121.5. Is it possible to chop (or add) some length and use the Archer I currently have installed???
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Old 09-26-2023, 06:33 AM
RV6_flyer's Avatar
RV6_flyer RV6_flyer is offline
Join Date: Jan 2005
Location: NC25
Posts: 4,234

Find a HAM Radio friend to explain it to you the signal loss between horizontally and vertically polarized radio signals.

Aircraft communication signals are vertically polarized and VOR Nav signals are horizontally polarized.

I find the signal loss between the two unacceptable to use for the other.
Gary A. Sobek
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To most people, the sky is the limit.
To those who love aviation, the sky is home.
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Old 09-26-2023, 06:37 AM
Carl Froehlich's Avatar
Carl Froehlich Carl Froehlich is offline
Join Date: Dec 2007
Location: Dogwood Airpark (VA42)
Posts: 4,438

Yes - you can modify it for comm. No, it will not work as well as a belly mounted whip.

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Old 09-26-2023, 11:22 AM
GEM930 GEM930 is offline
Join Date: Aug 2007
Location: Chico (KCIC) , CA
Posts: 271

I completely realize it will not work anywhere near as well. However, it is already installed, so trying it out will not be that big of a deal, that is assuming the modification is not all that complicated. Can anyone direct me to that information? Please.
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Old 09-26-2023, 11:53 AM
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Webb Webb is offline
Join Date: Oct 2007
Location: Jackson, MS
Posts: 1,961

Not enough sugar for the dime IMHO to modify.

But if you want to procedure, hereís the reference you seek.
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Webb Willmott
RV8 - Current Build
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Old 09-26-2023, 11:56 AM
BobTurner BobTurner is offline
Join Date: Dec 2011
Location: Livermore, CA
Posts: 9,271

You need to do two things.
1. Make it slightly shorter, to move the resonant frequency from nav (113 MHz) to com (127 MHz), or about 10%. E.g., cut about 2.5 - 3 inches off the end of the radiating element. Ideally you do this a little at a time, while monitoring the resonant frequency with an antenna analyzer, but this will be close.
2. Most important. Someone already mentioned polarization. In theory the antenna will not work at all if it’s horizontal. You want get as much vertical throw as possible in the leading edge (the diagonal part going from the ground leg on the rib, out into the wing). This is where most of the signal comes from. Since most wing tips are not symmetrical up-down, look at yours and see how to do this. I have stock -10 tips. I mounted the ground leg of the antenna to the end rib as high as I could, near the top. The leading edge of the radiating element, extending out into the tip, is bent down, until the long side is resting on the bottom of the tip.
This is not as good as an external, vertical antenna, but better than some believe. I have no problems at 20 miles. I use it mainly for atis, sometimes ground.
Edit. Also, don’t mount the antenna near the front of the tip. Mount it close to the ‘fattest’ (up-down) part of the wing, again, to maximize the vertical distance you can get.

Last edited by BobTurner : 09-26-2023 at 07:31 PM.
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