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DIY VOR/ILS diplexer?

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Ceengland

Joined: 11 Oct 2020
Posts: 391
Location: MS

Posted: Fri Dec 10, 2021 6:16 am Post subject: DIY VOR/ILS diplexer?

Good morning,

A friend needs to install either an ILS antenna, or acquire a diplexer to split his existing VOR antenna signal to feed both the VOR and ILS inputs on his Garmin 530. A diplexer would obviously be lighter & easier to install, but off-the-shelf models tend to cost more than an antenna. I thought that the Aeroelectric site had a circuit diagram for rolling your own diplexer, but I haven't been able to find it. Can anyone help with this?

Thanks,

Charlie

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Charlie

Eric Page

Joined: 15 Feb 2017
Posts: 245

Posted: Fri Dec 10, 2021 6:48 am Post subject: Re: DIY VOR/ILS diplexer?

Here's a program that will design the filter elements for a diplexer...



http://www.tonnesoftware.com/elsie.html



...and here's a video by Alan Wolke (W2AEW) explaining diplexers and demonstrating one that he built.



https://www.youtube.com/watch?v=wv79DSqVi9w

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Eric Page

Joined: 15 Feb 2017
Posts: 245

Posted: Fri Dec 10, 2021 7:14 am Post subject: Re: DIY VOR/ILS diplexer?

Or, if you don't mind laying out your own board, Mini-Circuits sells pre-made band-pass filter elements that are specifically designed for the VOR/LOC and GS frequency bands:



https://tinyurl.com/mtp67ycw+



https://tinyurl.com/yc2zt4d8+

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Eric Page

Joined: 15 Feb 2017
Posts: 245

Posted: Fri Dec 10, 2021 7:34 am Post subject: Re: DIY VOR/ILS diplexer?

Someone with more knowledge of RF wizardry could tell us whether this would work, but another possibility occurs to me.  Put a simple tee splitter on the antenna feedline, then in-line low pass and high pass filters feeding the VOR/LOC and GS receivers, respectively.  You would need some adapters to accommodate the filters' SMA connectors.



https://www.digikey.com/short/vf3vrnwj



https://www.digikey.com/short/hm2t9wtd

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nuckolls.bob(at)aeroelect
Guest

Posted: Fri Dec 10, 2021 8:41 am Post subject: DIY VOR/ILS diplexer?

At 09:14 AM 12/10/2021, you wrote:

  	  Quote: 	
		  --> AeroElectric-List message posted by: "Eric Page" <edpav8r(at)yahoo.com>



 Or, if you don't mind laying out your own board, Mini-Circuits sells pre-made band-pass filter elements that are specifically designed for the VOR/ILS and GS frequency bands:



  https://tinyurl.com/mtp67ycw



  https://tinyurl.com/yc2zt4d8



 	


  You need to remove the + signs from those

  links for them to work. Those would

  take all the uncertainty and post fabrication

  verification concerns. I've built those from

  discrete components but had access to test

  equipment to make sure they were working

  as desired.



  But then, these are experimental airplanes where

  you can do in-flight performance checks to see

  if your own design goals are met. Some pretty

  'soft' antenna systems have been found adequate

  to task.



  On the other side of the coin, what's your

  labor worth? There are numerous offers on

  eBay for about the same price as the Mini-Circuits

  devices . . . they're all packaged up

  and ready to go.



  https://tinyurl.com/yckhtnet



 

   Bob . . .



   Un impeachable logic: George Carlin asked, "If black boxes

   survive crashes, why don't they make the whole airplane

   out of that stuff?"

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user9253

Joined: 28 Mar 2008
Posts: 1921
Location: Riley TWP Michigan

Posted: Fri Dec 10, 2021 10:12 am Post subject: Re: DIY VOR/ILS diplexer?

Jim Weir has written articles about splitting an ILS signal from a VOR antenna.

https://www.kitplanes.com/tall-transmission-tales/

Note that his diagram shows an inductor but the text explains that a 10-picofarad capacitor with straight leads has enough inductance without a separate coil.

Below by Bob posted years ago:

Actually, you can fabricate a nifty antenna just from coax cable. In this case, you clean off the outer jacket of your feedline about 11". If it's a double shielded coax, strip of the outer layer of shield too. Pull center conductor out of the remaining shield as illustrated here:

http://www.aeroelectric.com/articles/shldwire/shldwire.html Stretch the center conductor and remaining braid out into a dipole and trim each to 8.5" per side. Glue to 1/4" wood or plastic dowel 17" long. Just spot it in a few places to fixture it on the dowel. Then put pieces of heat shrink over each leg of the dipole to "dress it up". This technique eliminates the process-sensitive and never pretty junction between antenna elements and the feedline. It's all one piece. Bob

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Joe Gores

Ceengland

Joined: 11 Oct 2020
Posts: 391
Location: MS

Posted: Fri Dec 10, 2021 12:13 pm Post subject: DIY VOR/ILS diplexer?

Thanks for the ideas. Ebay is certainly the best option, but I've passed 

on the various possibilities to my friend.



Charlie



-- 

This email has been checked for viruses by Avast antivirus software.

https://www.avast.com/antivirus

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Charlie

Eric Page

Joined: 15 Feb 2017
Posts: 245

Posted: Fri Dec 10, 2021 12:42 pm Post subject: Re: DIY VOR/ILS diplexer?

 	  nuckolls.bob(at)aeroelect wrote: 	
		  You need to remove the + signs from those links for them to work. 	


The + sign is a documented feature of the TinyURL service.  It causes their server to display a preview screen where the user can see the URL he’s being taken to, before actually going there.  It’s intended as a safety measure, to reassure users that they’re not being sent to a malicious website by an obfuscated hyperlink.

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Eric Page

Joined: 15 Feb 2017
Posts: 245

Posted: Fri Dec 10, 2021 1:01 pm Post subject: Re: DIY VOR/ILS diplexer?

 	  user9253 wrote: 	
		  Jim Weir has written articles about splitting an ILS signal from a VOR antenna. 	


I knew I had seen that recently!  Kitplanes republished that idea in the Dec 2021 issue, and Jim showed it built as a stand-alone device.  That part of the article begins at the bottom of page 2 in the attached PDF.

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Potpourri.pdf

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Aero 'lectrics, Potpourri, Jim Wier, Kitplanes, Dec 2021

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Potpourri.pdf

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