Steve wrote:
>>Greetings, TowerTalkians --
>>
>> I've got a local ham who can only install an HF vertical in a kind of
>>restricted spot. He can only put a couple of radials out but they'll have
>to be bent, shortened, etc. If you had to make this decision, which one
>would
>>you buy and install? All comments welcomed. Tnx.
>>
>>Cheers, Steve K7LXC
In due respect to the others who have commented on this topic,
I would suggest your local ham pick a single band, maybe 20 meters,
and put up a monoband Gladiator vertical. I have a 20 meter Glad up
and have done a lot of comparing with my Mosley TA-34, which is
up about 45 feet. The Gladiator vertical is up off the ground on a
Radio Shack push up pole, probably up 12 feet or so. The vertical
radiating element of the Glad is 17 feet 7 inches in length, so the
top is about 29 feet up when elevated on the RS pole. The radial
wires are 16 feet 8 inches long, and since they slope down at
about 45 degrees, they only go out about 11 feet 9 inches
from the pole. And, of course, the ends of the radials are just
a few inches off the ground. If one wants the radials completely
our of the way, just push the RS pole higher, and vertical element,
radials and all goes right on up as well.
There are several articles out now about the performance of
elevated radial monoband verticals:
1. Bill Shanney's, KJ6GR article in the Spring 95 Communications Quarterly,
an excellent piece, starts on page 71, and on to page 76
2. ARRL Antenna Compendium, Vol. 5, Al Christman's, KB8I, article on
Elevated
Vertical Antennas and elevated radials, page 11.
3. And Dick Weber, K5IO, has written an excellent article discussing 1/8th
wave long elevated radials as opposed to the usual 1/4 wave length.
He has both modeled and measured these and argues that the currents
are more likely to be equal in the shorter, inductive loaded radials, than
in the full length 90 degree length radials. Bob Meyers, developer and
source of the Gladiators uses and offers the 1/8 wave inductive loaded
radials. He told me at Dayton that he could perceive little to no
difference in performance using the shorter radials; he says only
a single inductor is required to load all four elevated radials.
Using these, the 20 meter radial lengths I discussed above would
be cut in half.
Oh, almost forgot to say where Dick's article is: Communication
Quarterly, Spring 1997, starting on page 9, and it runs to page 27!
How does the elevated 20 meter Gladiator compare to the TA-34
tribander. Not bad. In fact I use them both simultaneously!
With the FT-1000, I input the Gladiator to the BPF-1 external
receiving antenna input terminal. So, I am using antenna
diversity reception: horizontal polarity via the tribander,
and vertical from the Gladiator. From out here near mid-
Pacific, it is not surprising to hear the stronger DX signal level
being heard from the Gladiator vertical side. Because the DX
signal is arriving at a very low radiation angle, below the
peak of the main lobe of the tribander, but down where
the vertical is doing just fine in comparison. Of course
good low angle performance is the verticals "forte".
Don't forget, however, that the "gain" of a vertical is
around 0dB compared to a dipole, or at best a few tenths
of a dB gain, and often less than 0dB gain. It is all relative,
particularly when a beam's gain at the horizon, and often
for a few degrees above the horizon can be many dB
below 0 dB gain!! Have to get those beams up HIGH to
get any gain at all close to the horizon.
However, in general the vertical is usually about an S unit down
from the triband signal level. I have Gladiator verticals on seven
bands now, and have the 17/12 meter add-on verticals for the 30
meter mount on order: Three verticals all mounted side by side
on a single horizontal "boom".
I am fortunate in being able to operate antenna diversity on all
HF bands, as I have other horizontal wire antennas, or the tribander
for all the bands now, 160 up to 10 meters. Lots of very interesting
fun has been had, and I am anticipating a lot more as the sunspots
activity increases and the Fall low band season is only a few months
away.
The Gladiator will work great with just two elevated radial wires;
however, I am using four. These start up at the 12 foot or so
level, and slope down at roughly a 45 degree angle.
On the 160 up through 30 meter bands, I nearly always transmit
and rcv on the Gladiators, and input my long wires or inverted
V's into the FT-1000 BPF-1 terminal for the diversity reception
option. Again, this is because Hawaii is the most isolated group
of islands on the planet. The closest other land in about any
direction is around 2400 miles away! So nearly all of our signals
out here are coming in at pretty low angles!
Well, this has become too long. But I did want to point out the
option in a very limited space situation to pick just a single
band, put up a monoband vertical using elevated radials,
and have a great time on that band!!
Aloha and 73, Jim, KH7M
On the Garden Island of Kauai
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