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  #21  
Old 01-26-2022, 11:40 PM
BobTurner BobTurner is offline
 
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Quote:
Originally Posted by TASEsq View Post
Does the long arm need to be parallel to the ground plane arm? (The most outboard arm running fore/aft parallel to the rib?)
The ‘ground plane arm’ should be electrically connected (screws, rivets) to the end rib, which is the ‘ground plane’. By your description the outboard arm is parallel to the ground plane already. Whether the ‘arm’ is tilted up or down on the rib doesn’t matter.
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  #22  
Old 01-27-2022, 03:49 AM
TASEsq TASEsq is offline
 
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Quote:
Originally Posted by BobTurner View Post
The ‘ground plane arm’ should be electrically connected (screws, rivets) to the end rib, which is the ‘ground plane’. By your description the outboard arm is parallel to the ground plane already. Whether the ‘arm’ is tilted up or down on the rib doesn’t matter.
Thanks - I guess what I meant was: from a top view (horizontal antenna), does the outboard most radiating arm need to be parallel to the end rib, or can it follow the contour of the fibreglass tip (which gets wider as it moves aft)?

Hard to describe sorry! You can see what I mean by the shape of the cardboard template I’ve been working on.
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  #23  
Old 01-27-2022, 04:34 AM
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RV6_flyer RV6_flyer is offline
 
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Quote:
Originally Posted by TASEsq View Post
Thanks - I guess what I meant was: from a top view (horizontal antenna), does the outboard most radiating arm need to be parallel to the end rib, or can it follow the contour of the fibreglass tip (which gets wider as it moves aft)?

Hard to describe sorry! You can see what I mean by the shape of the cardboard template I’ve been working on.
My Archer antennae are on the TOP of the old style fiberglass wingtip and work extremely well. What I see in your photo will work just as well. It does not matter if it were along the bottom, middle, or top of the wing. A few degrees up or down makes little difference. Extending out from the last outboard rib and grounded / connected to the airframe rib or skin will work. My installation uses nutplates riveted to the fiberglass that is connected to the sheetmetal airplane with screws that hold the wingtip on.
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  #24  
Old 01-27-2022, 04:52 AM
TASEsq TASEsq is offline
 
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This is what I mean by “not parallel”
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  #25  
Old 01-27-2022, 05:09 AM
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emsvitil emsvitil is offline
 
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yes

https://www.pilotshop.com/catalog/av...r_antenna4.php

there's a few variations.........
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  #26  
Old 01-27-2022, 10:48 AM
BobTurner BobTurner is offline
 
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For optimum performance you’ll need to tweak the capacitor. But you probably should do that anyway.
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  #27  
Old 01-28-2022, 06:25 AM
TASEsq TASEsq is offline
 
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Well, didn’t take me too long to get it built tonight.

I left the top plate of the capacitor and the trailing arm long to trim them to size once I can find someone with an antenna analyser.

Apart from some nutplates to add to the last rib was a fun little project.
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  #28  
Old 01-28-2022, 08:56 AM
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Quote:
Originally Posted by TASEsq View Post
Apart from some nutplates to add to the last rib was a fun little project.
Most excellent! I really enjoyed building and tuning mine, works like a champ.

Dave
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  #29  
Old 02-12-2022, 11:39 PM
TASEsq TASEsq is offline
 
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Spent 3 hours with a very hospitable gentleman from my local HAM radio club today. After a bit of an antenna theory lesson (at least 10% even stuck) we moved on analysing the antenna.

I had to do it attached to the wing in the cradle so we moved the assembly away from the walls as best we could into the centre of the room. Initially it was resonating at 88Mhz and we ended up trimming off about 12”. I had left it waaay long and we knew we would need to trim it. In the end it came out right at 28.5” long - same as the plans indicated.

We got it resonating at 111Mhz (we think when removed from the room “ground plane” it will resonate a bit higher, but if it doesn’t 111 is a good number for the ILS). The SWR was approx 1.5 at this frequency.

At the 2 SWR line we get a bandwidth from 108-118MHz - spot on I think.

I didn’t have to trim the capacitor plate at all - which was weird because I made it slightly longer. I did use fibreglass not Bakelite tho, and it was 0.040 not 0.032 as per the plans, so maybe we fluked it. He did another test and showed the impedance was almost exactly 50ohms.

Anyway it’s all in theory - will be years before I fly it. But it was a great exercise anyway! Learned stacks - but still don’t understand how the gamma match capacitor works #pureeffinmagic.
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Last edited by TASEsq : 02-13-2022 at 04:40 AM.
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  #30  
Old 02-13-2022, 12:56 AM
TASEsq TASEsq is offline
 
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Here is the plot of the analysis - if anyone knows what the second graph means please elaborate!

https://drive.google.com/file/d/1h5q...w?usp=drivesdk
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