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[TowerTalk] Moxon questions

To: towertalk <>, antennas <>
Subject: [TowerTalk] Moxon questions
From: r miles <>
Date: Thu, 16 Dec 2010 11:58:40 -0500 (EST)
List-post: <">>
I have a problem with a 30m Moxon. It is a two element yagi with 
aluminium elements & wire to make the rectangle. The wire  is #16 silver 
coated stranded with teflon jacket. The wire broke yesterday at the 
element joints on one side of the rectangle. I assume one joint broke & 
the wire was hanging  vertical. The wind made the wire fatigue & the 
second wire to element connection failed & the wire fell  to the ground.
I used a Y or yoke arangement to tie the wire to the aluminium 
elements.I  didn't think the joint would fatigue in just 4 weeks but it 
did. I  might put in little eye bolts & hang the wire thru them with 
the wire tip bonded to the element end. That might  allow flexing & ease 
the stress on the wire.
I have been reading my ARRL antenna book this AM. I built it using 
Cebiks Moxgen formula. The boom is 12'10'' which was the software 
spacing for the Moxon. I am thinking of going to a basic 2 ele yagi. I 
can't change the  boom length. I would just add aluminium to the 
existing  elements. It would be apx. 6' 6'' to each side of the 
reflector & 5' 5'' to the driven element. The tips would probably be 
3/8'' taper to 1/4''.  A bit floppy in the wind but I think it would 
survive OK.
My question is the spacing. I'm guessing the  element spacing  @ 12' 
10'' is .23-.27 wave. It would be  the minimum I could get away with & 
still have gain & F/B. The impedance should be in the 40-60 ohm region. 
That is also close enough.
Mosley markets a TW32XL  2 ele WARC beam [trapped] with a 12' boom. It 
covers 30/17 & 12m. Commercial antenna makers of multi band trapped 
antennas play with the element spacing & boom length to get a close to 
50 ohm feedpoint impedance.
Anyone have any thoughts on my plan  or at minimum  how to  releave the 
stress on the wire /element connection?

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