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  #1  
Old 01-26-2022, 01:50 AM
TASEsq TASEsq is offline
 
Join Date: Aug 2017
Location: Melbourne, Australia
Posts: 428
Default DIY Archer plans

Has anyone built an archer antenna themselves? Shipping from the states is terrible at the moment.

Some specific questions:
1. Does the thickness of the sheet matter? I was thinking of mounting it on an angle riveted to the wingtip, and 0.025” seems pretty light weight and fragile (when the wingtip comes off).

2. I assume anything non conductive can be used an the insulator? (Like fibreglass or thin nylon etc?)

3. If I wanted it to be wider (wingspan wise) to reach to the outside of the wingtip fibreglass tip (this is on a -14) is it just a matter of scaling up all of the dimensions? (Including the size of the triangle and width of the strips?). Or does the triangle need to remain the same size and I can just extend the spanwise arm?

4. Am I correct that the shield of the coax needs to connect using brass hardware so it is grounded to the part attached to the wing rib? And the centre of the coax needs to connect to the small strip which is not electrically connected to anything?

Sorry if these are basic questions - all I really have to go on is the image on page 13-16.

Unfortunately I don’t have a lot of clues about antennae - I’ve read the aero electric connection but I’m more confused than enlightened.
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  #2  
Old 01-26-2022, 08:45 AM
Mousse Mousse is offline
 
Join Date: Nov 2012
Location: Deux-Montagnes, Qc, Canada
Posts: 173
Default

I built one exactly to this plan and am getting 80 m. range at 5,000'. Also used fiberglass for the small strip. .025" is fine. Easy peasy.

Michel
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  #3  
Old 01-26-2022, 09:24 AM
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RV6_flyer RV6_flyer is offline
 
Join Date: Jan 2005
Location: NC25
Posts: 3,880
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This is something that I have thought of doing for over 20-years. Since I knew Bob Archer and did not live far away from him, I purchased two of his nav antennae from him for $20 USD each. That was 30-years ago. The insulator material has been the part that I had the most concern over. My understanding is that it created a capacitance between the two pieces of metal and that was the secret to make the antenna work.

Good to know that fiberglass worked. May need to attempt to make my own for the RV-8 build. I did install two Archer antennae in my RV-6. One is used as an FM car radio antenna and the other for the SL-30 nav and glideslope. Typically can pick up a VOR 80 Nm at 5,000' just like Michel.
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  #4  
Old 01-26-2022, 09:51 AM
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Thermos Thermos is offline
 
Join Date: Jan 2005
Location: KASH
Posts: 623
Default

Hi Trent -

Some answers to your questions -

1. Material thickness does make a little difference in antenna performance. I used 0.025" and glued some foam to the outboard corners to protect them in the wingtip - works fine and should last a long time. You can also find some alternative mounting solutions on VAF.

2 If possible, use bakelite with the dimensions specified in the drawing. Although it does act as an insulator, it's actually there to be a capacitor that matches the antenna to your coax line and its dimensions are adjusted to do just that. If bakelite isn't available you can't use just any insulator, but fiberglass should work although you may need to adjust the thickness. This is more important if you plan to use the antenna for transmitting.

3. The total length of the antenna and the length of the individual "arm" sections are important and you shouldn't scale them - the antenna won't work as well. You may need to shorten the aft part of the "arm" to tune it for VHF.

4. You're correct about connecting the coax shield, doing that grounds it to the rib.

Do you know any ham radio operators? If you do, ask them if they have an antenna analyzer and can help you adjust the fiberglass thickness and antenna length. It's easier to do than it is to describe!

A couple of links that might help -

https://mightyrv.com/?p=4091 - my homebrew Archer antenna
http://www.vansairforce.net/articles...or_antenna.htm - instructions on rolling your own Archer antenna

HTH

Dave
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Last edited by Thermos : 01-26-2022 at 11:19 AM.
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  #5  
Old 01-26-2022, 10:01 AM
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rocketbob rocketbob is offline
 
Join Date: Jun 2006
Location: 8I3
Posts: 3,831
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Using an Archer antenna for VOR/GS is overkill and unnecessarily complicated for the task. A capacitively coupled antenna is not necessary for receiving a signal. A simple homemade bent whip antenna attached to the wingtip rib can be made from a BNC bulkhead connector soldered to a piece of welding wire. Works great. $60 NanoVNA can be used to tune it.
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  #6  
Old 01-26-2022, 10:27 AM
PilotjohnS PilotjohnS is offline
 
Join Date: Jan 2016
Location: Southwest
Posts: 2,174
Default My opinion

I believe for receive only, using bakelite, fiberglass or nylon should be adequate; the differences in their electric properties probably doesnt matter. But the thickness is what really matters. But as others have said, this is receive only, so things not as critical. i think the lengths are the most critical. JMHO.

I just went ahead and bought mine, because it was one less thing I had to make. (and I prefer not to play with arcy sparky stuff, this hobby is suppose to be fun)
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  #7  
Old 01-26-2022, 10:37 AM
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Carl Froehlich Carl Froehlich is online now
 
Join Date: Dec 2007
Location: Dogwood Airpark (VA42)
Posts: 3,597
Default

I’ve made many of these antennas. I do modify them to take advantage of the entire wingtip width by lengthening the arm that extends out into the wingtip as much as possible, then shortening the arm that runs aft to bring the antenna back into resonance. I typically use fiberglass for the Gamma match capacitor.

Some thoughts:
- I recommend moving the antenna aft on the rib to get it further away from the NAV/Strobes.
- I recommend not running NAV/Strobe or LL wire on the back of the antenna as suggested in the Archer instructions.
- Changing dimension as I describe moves the arm further away from the rib. For such quarter wave antennas most “work” is done by the first third of length from the feed point. The rest of the antenna brings it into resonance. Making this arm longer helps antenna performance. But keep the Gamma match “triangle” dimensions constant.
- I mount the antenna onto a piece of 0.032” angle and that angle is attached to the end rib with a couple of screws. The wingtip then just goes over the antenna.

Regardless if you buy or make this antenna, you need to turn it, both for resonance frequency (the overall length) and for impedance matching to the coax (the Gamma match). The Gamma match is adjusted by increasing/decreasing the insulator overlapping conductor or by increasing/decreasing the insulator thickness. None of this can be done without an antenna analyzer. If you don’t have a ham in the area to help, go in with you local EAA chapter members to buy one as a shared tool. It is a very good tool to check out any antenna install. Here is a standard one:
https://www.dxengineering.com/parts/mfj-259d

Carl
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  #8  
Old 01-26-2022, 11:00 AM
chaskuss chaskuss is offline
 
Join Date: Mar 2005
Location: SE Florida
Posts: 1,582
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Trent
#4 Do NOT use brass hardware. Brass and aluminum create a battery. You would be asking for corrosion problems. Best to use Cad plated steel hardware. [No, stainless steel hardware is not better, corrosion wise]

Charlie

Last edited by chaskuss : 01-26-2022 at 11:08 AM. Reason: added info
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  #9  
Old 01-26-2022, 11:05 AM
chaskuss chaskuss is offline
 
Join Date: Mar 2005
Location: SE Florida
Posts: 1,582
Default Frequency range used in Aviation Radios

Quote:
Originally Posted by Carl Froehlich View Post
snipped If you don’t have a ham in the area to help, go in with you local EAA chapter members to buy one as a shared tool. It is a very good tool to check out any antenna install. Here is a standard one:
https://www.dxengineering.com/parts/mfj-259d

Carl
snipped
Carl,
What frequency range meter do we need for our aviation antennas?

Charlie
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  #10  
Old 01-26-2022, 12:08 PM
Carl Froehlich's Avatar
Carl Froehlich Carl Froehlich is online now
 
Join Date: Dec 2007
Location: Dogwood Airpark (VA42)
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Quote:
Originally Posted by chaskuss View Post
Carl,
What frequency range meter do we need for our aviation antennas?

Charlie
108-137mhz
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