The sloping unterminated Vee beam is the easiest to implement. If you pick
your direction well, you can have an effective coverage off the forward
lobe, and the back lobe could be directed toward the longer path and low ham
populations, depending on beam heading of the open side. The Vee beam, if
put at quarter wave height or better for a band; is a low angle radiator in
the forward direction. You may think it is not working, as you might hear
DX stations well, when the propagation is most favorable between you and the
DX, (ie the main lobe covers an area between you and the DX that supports
propagation on a given band at that time). That applies to the horizontal
vee beam, and Ten Tec claims that for their models.
Our club followed the advice of another club that used less than quarter
wave high Vee beams for Field Day to work North America. Over the years,
we tried higher supports, and found indeed, the angle of take off dropped as
you went higher with the Vee wires. This actually eventually resulted in
our getting it too high to be effective for nearby states. We used 10 wave
legs (at 10m) which worked DX very well, but the beams did not work others
close in. From our central U. S. location, we used three vees to cover most
of the country. One aimed NW for example, also worked SE off the back. The
one aimed NE, did not have much in the way of ham population off its back
end, nor did the one aimed North, have much to the South. (South America
was not included as part of Field Day at that time). Thus the bi
directional response of unterminated Vees helped in one case, and had no bad
effect in the others.
Now if you raise the fed end, you still get low angles per Ten Tec web link.
One would expect some variation on the response of a half wave or longer
sloper antenna. The information on the Ten Tec site shows a nice 40 degree
wide beam pattern, and 25 degree angle of take off for 1/2 wave high feed
point. The beam height compresses when you go to 1 wave high, and you get
even lower angle of take off. (You get undesired multiple beams at higher
angles if you go higher than one wave).
A note on power. Someone complained that the antenna was power limited.
It is 100 watts CONTINUOUS duty, but in ICAS amateur Service, it is 250
watts or better. This is a function of the termination rating, and the
transformer. If you provided additional cooling, you could run higher
powers on an intermittent, (typically ham) duty cycle. This antenna is
obviously conservatively rated for the Ten Tec military customer. No ham is
continuously transmitting, thus, the antenna should be fine for DX,
contesting, etc. especially if unterminated.
At low elevations, our club found that 40 degree Vee angle was an effective
antenna. The Ten Tec graphs imply optimum angles are larger, but they are
probably calculating ideal half or one wave height examples.
With ladder line feed, we found that Vees are very forgiving of sag, leg
length, and angle. The tuner takes care of the matching. The inverted Vee
beams offer the chance to experience the joys of large wire antennas without
needing the lot length of the traditional horizontal Vee. You can also
convert the antenna to Inverted Vee operation by positioning the legs to 180
degree included angle.
I had thought my lot too irregularly shaped to do a Vee beam, until this
product came along. It looks like I can put an apex at the corner of my
lot and angle the legs to favor Europe. Normally, the club vees brought the
feed off behind the apex to the station. I will have to run feeder back
under the Vee. But, if I try to keep equal angles to each leg, I should not
perturb the pattern. Since the legs will not parallel my feeder in either
vertical plane nor horizontal, it should work. Time will tell.
-Stuart
K5KVH
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