N4XD wrote:
>The vertical and inverted-V both radiate poorly at 40-45 elevation degrees.
I would think that these radiation angles may be more useful than straight
up. There are relatively unrecognized antennas that can produce optimum
radiation at 40-45 degrees.
>The W8JK dipoles, fed 180 degrees out of phase, and at a height of 1/8
wavelength or more, produce a pattern that looks good for 160m DX. More
recently Belrose, VE2CV, wrote an article for QST, August, 2002, about his
horizontal loop design, broken into two loops, and fed 180 degrees out of
phase.
>These horizontal antennas need to be 1/8 wavelength high or higher to
develop the lower angle radiation patterns. Great advantages for the little
gun with his house, driveway, and streets preventing a good radial field, is
that horizontal electrical lines are reflected from the ground surface with
high efficiency at most incidence angles. This is truly a case where a
complete lack of radials should make little difference in performance.
Doug, there's a fly in the ointment here. To get 5.34 dBi @ 41
degrees
in VE2CV's loop, the 80m antenna is 15m high (48.6'). To produce similar
results on 160m, the loop needs to be ~100' high. I don't know about trees
for the average little gun's QTH, but those trees would have to be made of
steel at my QTH. If I were going to have 4 each 100' towers spaced 1/4 wave
apart, they would likely be in the form of a real 4-square (with a little
top-loading). A real 4-square over the same average ground VE2CV assumed
produces about 4.83 dBi gain @ 41 degrees, and a peak 6.8 dBi @ 21 degrees.
If I already had a 4-square, I'm not sure I would add a VE2CV loop for <1
dB @ 41 degrees, given the complexity of de-tuning it, etc. I certainly
would not put up 4 100' towers primarily to support a VE2CV loop. Just for
curiosity, I checked the gain of a VE2CV loop on 160m at 15 meters (48.6')
and also 1/8 wavelength (67') as you suggested. Here are the results:
15m (48.6') case: 1.99 dBi peak at 44 degrees
1/8 wl (67') case: 4.11 dBi gain at 44 degrees (similar to a 4-square)
30m (100' ref): 6.0 dBi peak at 41 degrees
So you can see this antenna is very height dependent. I've not included
any feed system losses which VE2CV did so my numbers at the same relative
height (i.e. 30m case) are higher than his, but you get the general idea.
The differences I sometimes see between my low and high angle
systems are truly staggering (i.e. ~10 dB) when conditions are right. I'm
not talking 2 dB but 2 S-units! I'll hasten to add that I would love to
have a VE2CV antenna for the same reason I cited before...you can never
have too many antennas. :-)
73, Bill W4ZV
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