[TowerTalk] Gladiator/Other 1/4 wave Verticals and Radial Count

[Jim Reid]

>Hi all,
>  Has anyone used the Gladiator verticals? If so I would appreciate some
>comment on there performance and durability.


I have all 10;  originally as monobanders from the TL160 all
the way up to the 10 meter unit.  However,  I now have had
to take the 160 and 80 down,  as a horse has come to
live in pasture where they once were,  and no room
nearby at the moment.  Have had to move the others
to the roof of the house,  and have converted all but the
40 meter units to the "tri-bander" configuration.  The 40
is now mounted above my beam at the top of the tower!
Pokes waaay up in the air now!

As near-the-ground mounted verticals with four elevated
radials they did work fine;  but I suspected that more radials
would have been better.  I had been planning to add a bunch
of ground/vine/bush crossing radials to create a good
ground field beneath all;  but then here came the
horses!

As the house roof is really not a good place for a lot of
radials,  and not enough room anyway,  I have converted
the units from 40 on up,  to center fed 1/2 wave verticals,
with the feed points elevated way up;  to around 38 feet
above the ground,  except for the 40,  which is up around
50+ feet to the feed point.

The 20, 15, and 10 half wave vertical set ups seem to be
down by around 4 to 6 dB from my C4 beam;  while the
40 half wave is comparable,  but more noise pickup than the
horizontal dipole on the C4. However,  I primarily am using
the 40 as a binaural/antenna diversity rcv'g antenna feeding
into the BPF-1 sub-rcvr input of my FT-1000D -- makes for
amazing "stereo" reception of signals,  especially on CW.
With a tuner in line with the 40,  I can get a good signal
for rcv into the sub-rcvr on each band above 40 this way.

If you cannot get a beam up above 30 meters,  by all means
the Gladiators are the next best thing.  On the lower bands,
you just need the space for the radials,  and I would add
more than the four Bob suggests.  You can probably
pick up 2 to 4dB of transmitted signal by increasing the
radial count, see below for predicted power increased
with increased radials using a ground mounted
1/4 wave vertical.

Per Paul Lee's book, "The Amateur Radio Vertical
Antenna Handbook",  the "theoretical" performance of
a 1/4 wave ground mounted vertical field strength would
improve as follows: start with only two radials, and out
at one statue mile set transmitter to read 115 millivolts
on an accurate field strength meter,  now adding radials
should do the following to the meter reading:

Increase radial count to 15,   FS should now read about 155 mV,
40 mV increase, or pick up in radiated power of +2.5 dB


Increase total radial count to 30,  FS should now read just
less than 170 mV,  or another 15 mV; power pick up
over 2 radials,  +3.3 dB.

Increase total radial count to 60,  FS should now read just
about180  mV,  or another added 10 mV;  power pick up
over 2 radials is now a +3.9 dB.

Increase total radial count to 113,  FS increases to about 185
or so mV, and a radiated field power increase of 4.1 dB over
2 radials.

Maximum possible improvement from a super number of radials
would be to increase the total FS to 196 mV (+4.6 dB) out at the 1 mile
point,
given that you started with 115 mV and only 2 radials.  BTW,  the numbers
above are comparable to those given in the ARRL Antenna Book in the
chart given therein about "Optimum Ground System Configurations"
in the chapter about  the effects of the earth on antenna operation,
thought
they go the other way around given loss of propagated energy as the
number of radials drops from a figure of 120 radials.


The field strength numbers above are what Lee gives in his chapter 2, Basic
Principles of Vertical Antennas, pg...21, Fig. 14.

Now,  I can find no references anywhere which give increased
power output Vs. number of elevated,  resonant radials as used
in the Gladiator system.  There are articles which discuss the
pattern influence Vs. radial count;  and also discussion about
the RF current in the elevated radials Vs.  their length and
what happens with inductive loading of the elevated radials
to maintain resonance,  but shorten their length.  But
no data reported which I can find about the radiated field
strength from such a system.

And it has been discussed on the reflectors,  again,  with
no real data presented.  There was a reported case of
a broadcast station using only a few elevated and
resonant radials;  and the field strength,  as I recall
did not pass muster.  I believe they were changed out
for ground placed and many more radials.

Note also,  that ground mounted radials do not need
to be a resonant length,  but do need to go out
far enough to collect as much of the return circuit
current as possible in copper, and not in the lossy
ground.

It is true that the elevated,  resonant radial,  only a few feet
off ground will couple electric field into the ground,  and
hence transmitter power will be dissipated there as the
resulting current flow will go somewhere,  and in the
process loose energy to the finite resistance of the soil.
Again,  no data to my knowledge.

And does my half-wave vertical configuration of the Gladiators
couple energy to the ground?  It is said that a half-wave horizontal
dipole will not,  since all the electric field lines on one half of the
dipole
find their complementary charge point terminations on the other half of
the horizontal wire.  And the high voltage at the end of the horizontal
wires,  if high enough,  will not propagate electric field lines into the
ground,  but to the other far end of the dipole.

However,  with my vertical half-wave dipole set up,  the lower wire
does come down toward the ground,  not close,  but a lot closer than
the center feed point,  or the upper far end.   Obviously,  there is
a greater chance that field lines from the lower end of this set up
could be tempted to couple straight on down to the ground,  induce
current,  though I have no idea how the current circuit would be
completed,  but if possible energy would again be dissipated
in the soil.  And again,  no data.

The only other place of which I am aware also using vertical half wave
dipoles,  is out at WWVH right here on the Island of Kauai.  They
use Rohn Towers,  with center insulators which were set up back
in 1971.  I do not know whether radial fields were placed under
them or not,  nor,  if they were,  again how the current return
circuit is completed,  given the elevated feed point used.
For example,  for the 2.5 MHz signal,  a tower about 196 feet
tall is used (1/2 wave at that frequency),  so the lower end of
the dipole is only several feet above the beach area where the
tower is mounted.  But it works;  and the intent of this signal is
only for Hawaiian local ocean area coverage.  The ground
wave is probably the intended path,  and not reflection from
the ionosphere,  but this is only my guess.  They also use the
half wave vertical for all other signals at 5, 10, and 15 MHz,
10 kW AM signals on each band (5 kW at 2.5 MHz).

Anyway,  hope this info goes toward answering your question.  And
yes,  the Gladiators are heavily made,  and will last as long as any
other aluminum tubular antenna set up.  The larger diameter tubes
are heavy walls,  and a lot of overlap is provided between joints.

73,  Jim, KH7M








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