Dear Wim:

Thank you for the additional information. The information fills in the
rest of the story.

Before I shut down the dedicated computer used for the calculations, I
looked at the last entry again. The 20.8 m high dipole in a 50 ohm system
seemed to have significantly smaller BW than what you reported. I changed
the impedance to 85.7 ohms and then found (using the same data) that the
SWR=2 BW is about 250 kHz. With a 1.3:1 turns ratio transformer, this is
also the expected BW that would be seen in a 50 ohm system.

In short, my reported BW numbers may need qualification. It is
interesting to see how two different simulation techniques reach similar
conclusions. I too expect that increasing the wire to 10 mm has little
effect.

Vacations can be very creative times. Thank you for your work. 73,
Mac N8TT

--
J. Mc Laughlin; Michigan U.S.A.
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"Wimpie" wrote in message
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On 11 abr, 06:14, "J. Mc Laughlin" wrote:
Dear Wim PA3DJS:

How I wish that I could read Dutch. However, in looking over all of
your work, it continually occurred to me that much of the base of
English
comes from Northern Nederland.

I looked at the first table on page 20 of your work. The
information so
intrigued me that I ran almost the same information through NEC4, which
does
well with antennas close to the ground. I assumed: a center frequency
of
3.6 MHz, a horizontal half wave dipole slightly adjusted to be resonant
at
3.6 MHz at each height, the use of Cu wire 2 mm in diameter, and earth
with
a sigma of 0.01 and a relative dielectric constant of 15. This is what
I
found without too obsessive an amount of tweaking:

The data is in this order:
height of the dipole in meters
the real part of the dipole's impedance in ohms
(the phase angle of the impedance was kept under 2 degrees)
the approximate SWR=2 BW in a 50 ohm system in kHz
the total apparent loss of the system in dB
(this is found by integrating gain in all directions)
the peak antenna gain in dBi

4.2 38.1 125 6.25 2.0
5.8 37.7 120 4.31 4.1
8.3 42.1 130 2.59 5.8
10.4 49.0 140 1.81 6.5
15 66.5 145 1.04 6.9
20.8 85.7 125 0.7 6.5

Most of my results are close to your results. It is interesting to know
if
I used the same assumptions. Please let me know.

I encourage you to consider translating your work, or at least parts of
it,
into English.

73, Mac N8TT
--
J. Mc Laughlin; Michigan U.S.A.
Home:
[rest removed]

Dear Mac,

Thank you for sharing your results with me. You are fully right, the
results are almost the same. The difference with my assumptions is
wire diameter only. I used 10mm. I expected more difference in useful
bandwidth, because of the factor 5 in wire diameter.

The simulations were carried out on IE3D with a lossy dielectric as
ground. The first table on page 17, shows the results for a perfect
ground.

I wasn't satisfied with the bandwidth, so the actual antenna consists
of 2 wires (1m separation). This gave me sufficient bandwidth to use
the antenna without a tuner.

The results between the brackets are with 3 floating reflector wires
under the antenna (about 1 m above ground). This gives an evident
increase in gain. The gain increases somewhat by raising the 3 wires
to about 1.5..2m above ground.

At this moment there are no plans to translate the document into
English language. As you have seen, the text in the images is in
English language, so you never know what happens during a vacation.....
The birdth of the Dutch version was in Spain.

Best Regards,

Wim
PA3DJS.