[SECC] Question about 30 meter halfwave vertical for the antennagurus
w8ji at w8ji.com
Wed Oct 20 07:54:44 PDT 2010
I got one of the 43' verticals from DX Engineering and was thoroughly
impressed with the construction and nice way it tilts up. I wasn't so
impressed with it's perfomance, but "nothing ventured, Nothing gained." It
may be location and/or radial configuration or something else, but I've gone
back to my OCF for 80/40 and a Bazooka for 160.
Anyway, I figured the vertical was only a little over 3' shy of a halfwave
on 30 meters and I have some aluminum rods that I could afix to the top and
make the 46' 3" length for the halfwave.>>
Speaking of all 43 foot verticals in general, I cannot conclusively find out
where the "43 foot thing" first got started. It appears to have started with
a vertical manufactured in Illinois.
My best guess is someone somewhere read Cebik's 88 foot dipole article,
which is NOT a good dipole idea for bands below 60 meters, and applied it to
a vertical by cutting the dipole in half.
The company that initially started this 43 foot idea used the wrong balun, a
voltage balun, and loaded the shield of the coax up. This resulted in a good
SWR because of system losses, but very poor overall performance. Of course
when someone with horrible antenna changes to a less horrible antenna or
when someone who has no other antenna at all starts making contacts, the
result is glowing reports of what they worked. It becomes a cult thing.
Eventually the balun on the Illinois antenna was corrected, and the
efficiency went up, but it is still an untuned vertical with a large
mismatch that depends on a tuner to have a low SWR. This means feedline
losses are somewhat high on many bands above 60 meters.
The 43 foot vertical will work fair on bands above 60 meters, but will not
be good at all on 80 meters and will absolutely suck on 160 meters. You'd be
very lucky to have 1 or 2% efficiency on 160.
IMO it is an OK 60-10 meter antenna.
<<I did a little searching on half-wave verticals and got mixed answers on
radials--a couple said use the full compliment of radials like a 1/4 wave
vertical, but more seemed to lean towards a counterpoise (single radial if
you will) at a half-wave.>>
I do not know why people would say 1/2 wave, other than people commonly just
say things without having the faintest clue what they are talking about. The
worse possible counterpoise length other than near zero would be a 1/2 wave
resonant counterpoise, so get a pen and scratch those people off your
advisors list. :-) Any length vertical, from zero to a half wave or longer,
if you are using a tuned counterpoise, should have the lowest impedance
counterpoise possible. That would be 1/4 wave or an odd 1/4 wave resonance.
A 1/2 wave would be a very high impedance, almost like no counterpoise at
all if it is elevated and resonant.
Perhaps they are using that old incorrect wives tale that radials should be
as long as the vertical is tall.
If these are in ground non-resonant radials, you would simply want as many
radials as you can manage as long and straight as possible.....but anything
over 20 or 30 radials and .2 wavelengths is pretty much a waste of felt and
fur. With a half wave, you don't even need that.
The absolute truth is the shorter the vertical, the more critical the
radials and other things that add resistance become! The old common myth
about needing radials as long as the antenna is tall is clearly false.
<<Anybody ever try this and if so how did it work and what is the
Well, I've measured this stuff here. On 40 meters a 1/4 wave vertical
flattened out in field strength with about 12-15 buried radials. Adding more
wire was mostly a waste of wire. 12-15 buried random length radials were
about even with 4 elevated tuned radials 8 feet high on 40 meters. This of
course is in my soil, but that data was using good field strength
measurements with real meters.
Since field strength pretty much stopped increasing, I never measured more
than 30 radials.
I have more radials than that on my 160 tower (it has 100 buried radials
between 150 and 250 feet long), but mostly because of lightning and because
I hang other antennas over that field. On my 40 meter 4 square, I used about
25 radials 1/4 wave long on each element.
I think a remote tuner would be a very good investment with a 43 foot
vertical. If the tuner does not explode or catch fire, your system should
have pretty good efficiency from 80 through 10 meters with a remote tuner. I
would not bother making the vertical 1/2 wave long on 30 meters. I would
match it the way it is.
If I ever put an HF vertical up here, it will be a Hy-tower or a trap
vertical like a 6BTV. The fact is almost any dipole at reasonable height
will beat a vertical on higher bands, and since I have reasonable height I
have little need for a vertical. The only bands verticals seem to really
shine on are 160 and to a lesser extent 80.
We do, after all, have poor soil with high Fresnel region losses on higher
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