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Wingtip VOR antenna . . . a clearer picture

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nuckolls.bob(at)aeroelect
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Posted: Wed Mar 28, 2012 5:43 pm Post subject: Wingtip VOR antenna . . . a clearer picture

At 07:45 PM 3/28/2012, you wrote:




Bob,



Thanks for this drawing. It gives me a general idea of what this thing is -

I could almost build one from it...  A few more dimensions would be very

helpful. (or else I'll have to get out my trig calculator)



    Or lay it out on a sheet of paper.  Agreed, my dimensioning

    would get me a strong reprimand from the checkers at the

    last place I did any drawings for production release. That

    would have been Electro-Mech about 30 years ago!

My wish list:



1. Explicit dimensions for length of each piece



    They're pretty much there . . .



2. A label for each piece.  For us antenna ignoramuses (or is that

ignorami?) I cannot differentiate between the "antenna" and "ground strut".



    Do some research on how this antenna is mounted to the

    the airplane. The ground strut attaches to the tip rib

    of an all metal airplane.



3. Call-out fastenings and their positions. Are they critical? (e.g. can I

substitute a #4 machine-screw & nut instead of a 3/32 dia. aluminum rivet or

a #6 screw or a #8, etc?)



4. Some very explicit instructions about how to connect the feed line:

    a. how to prepare the shield (I'm assuming a coax feed line)

    b. type of wire terminals (or is it soldered?)

    c. or can a coax connecter be installed on the antenna



5. How is the structure mounted in the airplane?



    I hesitate to do highly detailed instructions on Bob

    Archer's product. The amount of information I do offer

    is intended as a guide for exploration. The first principal

    of experimental aircraft is education. If I were to craft

    such a product, it would indeed feature a captive coax

    connector. The 'sketches' I offered are intended to get

    you into the ball-park - not to replicate Bob's product.



How did you measure the capacitance? As someone who knows nada about RF, a

spec like X pf at Y freq fascinates me..



    I have a LRC meter that displays inductance, resistance

    and capacitance on a digital display. Really useful.



http://tinyurl.com/8ygt4mq



    If that meter had not been at hand, I would have wound

    a small coil of wire, hooked it across the unknown capacitance,

    taken a resonance reading, added some known capacitance and

    taken another reading. You can do this with a 'grid dip' meter.



    The one I have is about 50 years old



http://tinyurl.com/6s875rp



    but probably the best one ever made. It's good to 1%

    of reading or better.



    Suggest you get a sheet of paper and make

    a full scale drawing of the finished assembly and the

    component pieces. Strike up some conversation with

    others here on the List about the various questions

    of techniques you have cited. I think the dimensions

    given will bound your options.



    You're going to become a wingtip VOR antenna expert . . .

    or at least a guy who has "been there, done that." I

    think there's enough data there to get you off to a good,

    low risk start.

   Bob . . .

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nuckolls.bob(at)aeroelect
Guest

Posted: Wed Mar 28, 2012 5:43 pm Post subject: Wingtip VOR antenna . . . a clearer picture

At 06:23 PM 3/28/2012, you wrote:

 	  Quote: 	
		  



Bob,

Did you install the new cap or jhust test it by itself?


	


   No, just measured it free and took some dimensions. Found

   that the .31" and 5.0" dimensions in my earlier sketches

   were in error.

   Bob . . .

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JLuckey(at)pacbell.net
Guest

Posted: Wed Mar 28, 2012 6:51 pm Post subject: Wingtip VOR antenna . . . a clearer picture

I apparently mis-understood the purpose of your posting.  I thought it was

to provide complete instructions & how-to. (and I thought it was a little

odd that there were omissions, since your documentation is usually

hyper-meticulous)



 	  Quote: 	
		  From what you've provided, one can certainly deduce the remaining

dimensions.
	




However I still need help on nomenclature.  The ground strut is the

horizontal 1.5 in wide piece shown at the bottom of your drawing. Is that

correct?



I was wondering about how Mr. Archer played into this situation.  I, too,

have some level of discomfort simply copying his design, and I believe that

this antenna is available for < $100.  At that price, it hardly pays to

do-it-yourself except as an educational exercise.



Also, I'm interested in connecting a coax connector directly to the antenna.

Do you feel comfortable elaborating on that topic?



-Jeff



--

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nuckolls.bob(at)aeroelect
Guest

Posted: Thu Mar 29, 2012 12:13 pm Post subject: Wingtip VOR antenna . . . a clearer picture

At 01:56 PM 3/29/2012, you wrote:

 	  Quote: 	
		  



Bob



Ok now I have a problem ,at the weekend I made the VOR antenna to 

the dimensions previously discussed/aero electrics book I 

believe,these are very different to the ones shown on the previous 

link ,which should I use?


	


     The dimensions I published originally were

     parroted from an article in an Van's Air Force

     publication . . . probably 10-12 years ago.

     It was not until I put my hands on a 'real'

     antenna (thanks to Don S) did I have an opportunity

     to check/update the VAF drawings.



     Are you flying or close to flying the earlier

     'version'? It would be interesting to do a

     seat-of-the-pants observation on differences

     in performance. You could build up a 'new'

     antenna but keep it in reserve until you've

     flown the 'old' one.



     I'm thinking that it would be difficult to

     tell much difference from the pilot's seat

     but you might perhaps dispel that notion

     for me.



     The question that started this thread involved

     procurement of 1/32" Bakelite . . . while in

     fact, 1/16" Phenolic is the 'real' material.

     It was something of a windfall that other

     discrepancies were discovered. Sorry 'bout that.

   Bob . . .

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