[Boatanchors] antenna question

[hwhall at compuserve.com]

 I suspect the traps aren't specific to the number of elements or the spacing. The elements in a yagi are just dipoles (halfwave elements) tuned slightly differently (reflector is a bit lower and director a bit higher than driven element) and spaced a certain way. I don't think the other 2 elements "know" how the 3rd element was made to resonate at its particular frequency.  For example, numerous yagi like arrays are made with bent & folded elements and the antenna still works.

If it's not too hard to get yours on the ground, try making the transplant, prop the results up on a tall ladder and give it some RF.  I bet it will work.  Do you have some antenna analysis tools besides an SWR meter?  

 
Wayne
WB4OGM

 

-----Original Message-----
From: RAY FRIESS <rayfrijr at msn.com>
To: boatanchors <boatanchors at mailman.qth.net>
Sent: Thu, Feb 18, 2016 11:29 pm
Subject: [Boatanchors] antenna question

Need some advice or observations from antenna guys here.
I'm wondering how much interaction there is between traps and spacing in triband beams?    I know that the antennas are designed with certain spacing between the three elements, and what the traps in each do, which is basically to present a resonant length for each band, using
the traps.

Here is what I am thinking:  I have a three element beam that has a bad trap in one side of the driven element.  It is
a Hygain triband.   A friend of mine had his 50 foot tower come down today in 85 mph winds.  On top of it, he had
a Mosley Classic 33.  The driven element seems to have survived with minimal damage.
 What I am wondering is, can you "transplant" the Mosely driven element to the Hygain, using
the current spacing of the Hygain.   In other words, everything would remain the same with the Hygain, except the
driven element would be removed and the driven element from the Mosley would replace it.  Or, are the designs
so different that the spacing of a triband elements depends in part on the design of the traps?

I thought it might be possible because each driven element is resonated on the three bands with its own traps.
If the driven element of one was transplanted to the other, the three elements would still be resonated with the
traps they have.  OR, is the spacing of the elements dependent on the traps too?
 		 	   		  
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