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[Towertalk] Phasing Lines For Stacks

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Subject: [Towertalk] Phasing Lines For Stacks
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Date: Wed, 21 Aug 2002 19:01:16 EDT
For years I have used stacks and have used two equal pieces of coax to each 
antenna from the remote antenna swtch on the tower.  As anyone who has a tall 
tower in Florida will tell you, the remote antenna switches on towers get 
fried from lightning hits on a regular basis and it is really a pain to 
replace them and wrestle all the phasing back onto a new antenna switch every 
couple of years.

At my new location I have been running parallel 75 ohm hardline of equal 
lengths to each antenna and do all the switching BIP/BOP/TOP/BOTTOM in the 
closet with the Ameritron antenna switch.  Obviously, the chances of the 
boxes getting fried in there are just about nil.  However, since the top 
antenna (in this case a 40 meter beam) requires an extra 100 plus feet of 
coax, so the lower one has an extra 100 feet that must be coiled up outside 
the shack...rather unsightly and unwieldy.

I have come across a huge amount of Heliax (1 3/8 inches) and am planning on 
replacing the 75 ohm hardline.  I am still plannning on using parallel feed.  
However, I don't want to waste the Heliax by rolling up the extra 100 plus 
feet on the second line.  Plus again, it really takes up a lot of space.

The question however, is this. Must the two pieces of Heliax be exactly equal 
in length?  Or, can they a multiple of a wavelength longer as measured by my 
MFJ 259?  If so, do they have to be a full wavelength longer or can it be 
just a multiple of a half wavelength?  My gut feeling tells me that 
everything would be fine if added an extra full  electrical wavelength. I 
think just using multiples half an electrical wavelength would put them into 
out of phase.

I hope this post wasn't too rambling and would like to hear from the experts.

Bill K4XS

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