I have three f12 C31XR's here - up since Dec of last year. Not
that it is anything spectacular but in 11 weeks I have managed
to work over 200 countries from out here in AZ (no contests
included) - not an overly easy task at this time of the sunspot
cycle as well as from out west. [Heights 121', 81', 41']
I can say MOST of the time the stack is the best of the bunch -
on 20 rarely is there much difference between it and the single
antennas. But that is to be expected. Some of the times it is
indeed stronger - as much as an S unit on 20 and I have seen
three S units on the other bands (for the stack versus the worst
antenna). The "best" differential I have seen was on 10 - where
the stack and top antenna were as much as 20 db down from the
LOWEST antenna (to the Caribbean). Height is indeed more
important than gain. Being able to select various heights is an
advantage - not all the time - but an advantage nonetheless that
comes into play. I remember once in a DX contest I temporarily
installed a 6 el KLM 15 at 28' ... it was WAY below the "main"
antenna (Hygain 5 el at 85') in signal strength except when the
band was going out - all of a sudden there was as much as a 20
db difference with the lower antenna being stronger!
Phasing IS critical - when I first installed it, using Unadilla
baluns (junk in my opinion due to mechanical construction) I
found that whenever the center antenna was included the signals,
even the noise level, went down. We suspected (and WX0B had
said) bad phasing but all were constructed the same. We checked
it out and sure enough the center balun was wired differently
INTERNALLY! Changing this made a big difference.
As far as being competitive - hard to say definitively at this
point but I can say it holds its own even going east - breaking
through the east coast wall to EU or AF often with just 100W is
a great feeling!
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