[VHFcontesting] Dual Band Yagi question

[Alex]

> Jeff Embry, K3OQ wrote: 

> but would like to have a dual band yagi
> for 2 and 432 that is easily assembled and dis-assembled for use will
> I am on vacation and particularly in the contest.  A single feedline
> is preferable, but can deal with two if I have to.

Hi Jeff,

Just a word of caution, don't be tempted by 2m and 70cm models that share a
single boom and a single feed line for weak signal work. The 70cm antenna
will not work properly for horizontal polarization.

I've tried 2 Cushcraft A270-10S antennas in all possible configurations
(stacked, one horizontal, one vertical, ...) at 30ft and found that the main
lobe of the 70cm antenna (when mounted horizontal) is about 90 degrees off
from the main axis, and that lobe had less gain than a 4 stack of loops @
25ft. I checked this on both antennas to confirm my findings. Even replacing
the steel mast in the rotator with a wooden one didn't make a difference. As
a vertical antenna for repeater work, they work just fine, but when you
mount them horizontal, you have a decent 2m antenna, but forget about the
70cm portion.

Think about it....how often have we seen threads on this list about how far
apart to mount a 2m and 70cm (or some other -) antenna on the same mast? The
answer has never been "slap 'em on the same boom and add some matching stubs
to get a decent SWR". :)

If you require a single feed line, then try a log periodic as others have
suggested. 

Merry Christmas to all!

73,
--Alex KR1ST
http://www.kr1st.com
http://airlinkexpress.org