[TowerTalk] Side by Side, Elliptical polarized yagis for 6m?
Wed, 25 Jul 2001 14:40:51 EDT
In a message dated 7/19/01 2:21:35 PM Pacific Daylight Time,
firstname.lastname@example.org writes: <<
Mike VE9AA here.
Brand spanking new to the list and I am going to fire off a question right
off the bat.
Has anyone tried side by side, each slanted 45 degrees, (tops pointing
towards one another), fed IN-PHASE
for elliptical polarization? (I don't want RHCP/LHCP)
I am primarily a 6m DXer so local tropo, EME, etc. usually does not interest
I'm thinking of a pair of the K6STI long 5 elements spaced 5/8wl apart up @
58' or so.
Have 5 "other" 6m antennas here, so wanna try something "new".
Michael, Coreen & Corey Smith
(VE9AA, VE9AAA & Baby)
271 Smith Rd
Any polarization coming in that is different than you have, it can be
effective as the angle of radiation is different if at the same height as the
other antennas. If I were to do this I'd model it in Eznec along with all
the other antennas you have at the same height and see what the major angle
of radiation is over real ground. If it's different than the rest it can be
of some value if you can switch between them on receive. Are you sure the
polarization is elliptical with your configuration?
On a blind call you are not sure what the optimum angle is on transmit
without first making the contact and then running comparisons. If it is at a
different height than the rest it could have about the same angle(s) of
radiation as the rest and be of little value. Being of the same polarization
(or mostly) as of what is coming in is always an advantage but it's not
always constant as polarization shift occurs. I have a beam with 6
polarization's and switching between them eliminates about 75% of the QSB
which is a significant advantage--all the time.
If both are at 45 degrees to a vertical masts there will be RF coupling to
it, distortion to the pattern and degraded performance. Quads have an
advantage of bottom feed where the feedline is mostly out of the direct
antenna field. With a fiberglass mast you could get 45 degree polarization
from corner feed and very little coupling to supporting metal members below.
Horizontal yagis have very little coupling to a vertical tower. I ran
patterns with the simulated tower and mast and found horizontally polarized
Quads with their bottom feed have more coupling to a tower than a yagi. It
can be reduced with an insulated coupling(s). The 2 element tapered quad
fiberglass elements had less RF absorption to the mast/tower than a 2 element
with a 8' boom. K7GCO
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