TopBand: Top Hat Loaded Verticals

[k***@juno.com]

John, W1FV, has been using ~41 foot tall verticals for many years on
80M. They use the top set of guys as the loading and are arranged in a
triangle array with 1/8 wave spacing. John has one of the best 80M
signals on the East Coast.
He has also developed a feed method to drive all three verticals as one
single "fat" vertical on 160M. His signal on 160M is also outstanding.

I haven't a clue as to efficiency, feed impedences, radiation
resistances, ground losses, etc.
So, while the technical discussion rages on, it is interesting to note
that another ham has excellent results with short, top loaded antennas on
Topband.

73....Carl KM1H

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[K***@aol.com]

Carl;
My 80 meter four-square is very similar;
each vertical about 43 ft. tall with 3X top loading wires grounded to
vertical via s.s. clamp.
A 160 meter version is 90 ft. tall with top-loading wires, which also serve
as the upper guys.
73-
Jim

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[John Kaufmann]

Post by k***@juno.com
John, W1FV, has been using ~41 foot tall verticals for many years on
80M. They use the top set of guys as the loading and are arranged in a
triangle array with 1/8 wave spacing. John has one of the best 80M
signals on the East Coast.

Thanks for the plug, Carl! Actually in its first incarnation, I did
use 40 foot verticals, but they are now 61 feet tall. This is still
somewhat short electrically on 80, so I do use the top set of guys
to obtain some top loading to resonate the system on 80.

Post by k***@juno.com
He has also developed a feed method to drive all three verticals as one
single "fat" vertical on 160M. His signal on 160M is also outstanding.
I haven't a clue as to efficiency, feed impedences, radiation
resistances, ground losses, etc.

I do indeed drive all three verticals in phase on 160 and switch in base
loading coils to resonate them on 160. Each vertical by itself has a very
low feedpoint resistance. With a laboratory grade General Radio impedance
bridge I have measured the feed resistance (with loading coils in place)
to be about 7 ohms. Compared to theoretical modeling predictions for my
antenna over perfect ground with no resistive losses, I infer a loss resistance
(primarily ground and and some loading coil) of around 2-3 ohms. The radial
system consists of over 100 ground mounted radials per vertical, with most of
the radials in the range of 60-100 feet long. However, when all 3 verticals
(spaced 35 feet) are driven in phase, the mutual coupling between the elements
drives the radiation resistance at each vertical up to around 15-20 ohms (which
is a calculated number and is hard to measure directly). This improves the
efficiency by making the actual antenna gain less sensitive to loss resistance.
The 2:1 SWR bandwidth on 160 is only about 60 kHz, but almost all my
operation is
around the 1830 window, so this is not a problem. Using top loading on 160
instead
of base loading would theoretically be even better, but would complicate the
dual band 160/80 operation capability, since switching the loading is harder to
do at the top of the antenna than at the bottom. In any event, it is possible
to make fairly efficient short vertical systems, but much more attention must
be paid to reducing losses than for "full size" antennas.

Post by k***@juno.com
So, while the technical discussion rages on, it is interesting to note
that another ham has excellent results with short, top loaded antennas on
Topband.
73....Carl KM1H

73, John W1FV


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[w***@postoffice.worldnet.att.net]

Post by k***@juno.com
John, W1FV, has been using ~41 foot tall verticals for many years on
80M. They use the top set of guys as the loading and are arranged in a
triangle array with 1/8 wave spacing. John has one of the best 80M
signals on the East Coast.

I do the same thing on 80 Carl. My 35 ft 80 meter vertical
compares quite well against a 130 ft long dipole up at 130 ft on 80.
I use about 60 radials 70 feet long on 80.

In Sylvania Ohio, I used the same setup on 160. The upper guys of a
70 ft tower top loaded the vertical. A three wire hat doubling as
guy lines worked quite well.

In short radiators, as the radiator's PHYSICAL length is cut in
half, radiation resistance goes down four times. That means
ground loss will be FOUR times higher (with the same ground system)
if you make the antenna half the PHYSICAL height.

No amount of wire folding, bat wings or chanting while dancing
around a fire will fix the problem.

73, Tom

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[Fred Hopengarten]

From:
Fred Hopengarten K1VR
617/259-0088
Six Willarch Road
Lincoln, MA 01773-5105

Post by k***@juno.com
John, W1FV, has been using ~41 foot tall verticals for many years on
80M. They use the top set of guys as the loading and are arranged in a
triangle array with 1/8 wave spacing. John has one of the best 80M
signals on the East Coast.
He has also developed a feed method to drive all three verticals as
one single "fat" vertical on 160M. His signal on 160M is also
outstanding.
I haven't a clue as to efficiency, feed impedences, radiation
resistances, ground losses, etc.
So, while the technical discussion rages on, it is interesting to note
that another ham has excellent results with short, top loaded antennas
on Topband.
73....Carl KM1H

K1VR adds: Everything Carl says above is true. I'd like to add to the
discussion.

John (W1FV) also had great concerns about efficiency. He carefully
measured feed impedances, created a matching system, and minimized ground
by installing an extensive ground system (soldered at each intersection)
before seeding the lawn at his newly constructed house. It is not
inconsequential that John is a very smart cookie, holding a BSEE from MIT
and a Ph.D. (EE) from Cornell, and able to use lab equipment from Lincoln
Labs to do his measurements.

As I recall it, Sevick (W2FMI), in a QST article during the 1950's,
"proved" that short verticals can work very well, as long as the ground
system is carefully built (to keep ground losses low) and the 50 ohm coax
is efficiently matched to the very low impedance short antenna
(transitioning 8 ohms, or whatever it may be, back up to 50 ohms).

While Carl, KM1H, is pointing out that short verticals with a top hat can
work very well indeed, he is modestly not mentioning that his own station
performs unusually well because he too has paid attention to creating an
extensive ground system and carefully matching the feedline to the
impedance present at the feed.

Conclusion: He who doesn't waste too much power, by ground losses and/or
with an inefficient feed system, can be happy on topband.

P.S. My own topband antenna still needs improving, both in terms of
ground losses and feedpoint matching.


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[Joe Subich" (Joe Subich)]

Post by k***@juno.com
So, while the technical discussion rages on, it is interesting to note
that another ham has excellent results with short, top loaded antennas
on Topband.

We have all seen good operators with less than optimum antennas in a superior location beat an average operator with "textbook perfect" antennas. With short, top loaded antennas, one generally has the best performance possible in a limited height ... that doesn't mean the top loaded antenna could not be improved by the addition of a superior (broadcast grade) ground system or by replacing the top loading with additional antenna height. Every one of us makes compromises based on available resources. I worked my 160 DXCC in the early 80's with nothing more than a half-sloper because I was too lazy to install a good ground system and shunt feed the big tower ... that doesn't mean that the half-sloper was the best antenna.

Tom (W8JI) has coinsistently attempted to debunk the "old fart's tales" currently being applied to lowband antennas. He has provided theoretical data from the most respected antenna scientists, not some "explanation" or anecdotal results from an antenna marketing flier. He has provided actual field strength measurements from working antennas under controlled dondfitions, not a "guess" from modelling programs known to have systemic errors under the conditions being tested.

I guarantee you, if I were to erect a 17' tall "T" antenna or a 17' tall "pi" antenna they would perform exactly the same as any other 17' tall top loaded antenna over the same ground system as long as the losses in the feed (matching) network remained the same.

It's time to put the issue to bed. If you have an antenna that works well for you, fine -- use it, even recommend it, but DON'T make exagerated, scientifically unsound claims. If you do, and I don't care who you are, be prepared to back up those claims with sound, scientificly valid data made under controlled conditions.

73,

... Joe Subich, W8IK ex-AD8I
<***@ibm.net>
<***@ibm.net>


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[Frank Donovan]

The technique John describes to significantly reduce the ground losses in
his short 160M verticals is well known by antenna engineers. One of the
best references is IEEE Transactions on Antennas and Propagation,
November 1973, "An Array Technique for Reducing Ground Losses in the HF
Range." This article describes how inefficient vertical radiators can be
arrayed together to improve their net efficiency. The improved efficiency
results from reduced ground losses brought about by the array's lower
ground energy density simply because the total energy is spread over a
larger ground area.

This method is also commonly used to reduce the losses of Beverage
antennas operating in the HF range by arraying three or more closely
spaced Beverages. Three Beverages spaced side-by-side separated by a
distance approximately equal to their height above ground improves the
efficiency by approximately 3 dB compared to a single Beverage for typical
soil conditions.

73
Frank
W3LPL

Post by John Kaufmann
I do indeed drive all three verticals in phase on 160 and switch in base
loading coils to resonate them on 160. Each vertical by itself has a very
low feedpoint resistance. With a laboratory grade General Radio impedance
bridge I have measured the feed resistance (with loading coils in place)
to be about 7 ohms. Compared to theoretical modeling predictions for my
antenna over perfect ground with no resistive losses, I infer a loss resistance
(primarily ground and and some loading coil) of around 2-3 ohms. The radial
system consists of over 100 ground mounted radials per vertical, with most of
the radials in the range of 60-100 feet long. However, when all 3 verticals
(spaced 35 feet) are driven in phase, the mutual coupling between the elements
drives the radiation resistance at each vertical up to around 15-20 ohms (which
is a calculated number and is hard to measure directly). This improves the
efficiency by making the actual antenna gain less sensitive to loss resistance.
73, John W1FV

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