Rick Mintz wrote:
Greetings all:
I want to phase two Butternut HF-2V 40/80 verticals.
Additionally I need to switch the phasing line so as to have a N-S and E-W
directionality. 40 meters is the most important band in terms of the needed
efficiency. Anyone done this and have some specifics?
Rick W1TY
Being you want to go both directions, you will probably need to
use a compromise spacing that affords near equal gain in both
directions...Naturally, this will compromise maximum gain, but
not too much you can do about that, being in one direction you
will be running a broadside array, and the other, an endfire array.
The spacings for max gain are quite different for each type.
In general, max gain for a broadside array is about 5/8 wave
spacing. An endfire array, somewhere around 1/8 wave. So I'd
probably use something like a 1/4 wave spacing to make both
directions appx equal gain. You could model this, if you wanted
it real close...Naturally, on other bands, this will all go
out the window...But if you used the 1/4 wave spacing on 40m,
at least you could run an endfire array on 80m, using the close
1/8 wave spacing. The max gain of a wide spaced broadside array
is slightly higher than the max gain of a close end fire array.
But if you fed with a wider 5/8 WL spacing for max broadside gain,
it will be too wide to feed as a decent endfire array in the
other direction."2 db less than 1/8 wl spacing"
You could feed with 1/4 wave spacing for 80, and have 1/2 for 40,
but ditto again..You will lose a bit endfire.."about 1.5 db less"
If you use 1/4 wl spacing , the difference between the two
directions will be only about .5 db using 90 and 180 degrees
phasing , for broadside, and then endfire. You can try other
phasings and get even more patterns...
There are graphs in the antenna handbook.
Also, there are articles in the antenna handbook on
how to feed them. The simplest method I use, just being changing
feedline lengths...You don't really need a phasing line, per
say...IE: if you want to feed one element 90 out of phase from
the first, just add 90 degrees "1/4 wave" of extra feedline to
the second element ...Consider the velocity factor, etc...
There is plenty of info on all this in the ARRL antenna handbook.
http://web.wt.net/~nm5k