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.