Rick,
I built two DHDL-s last week for the 160 m contest from C6AGU. One was
pointed towards EU and the other one towards NA/JA. The EU one was longer at
19 m vs. 16 m for the NA one. The two antennas behaved quite differently,
with the EU one being excellent and the NA one very mediocre.
I was surprised because I have had two similar DHDL-s in November in the
same spots. They were both 16 m long and 6 m high, and they were both very
good. But, I "tuned" those antennas by adjusting the loading resistors for
the lowest signal from the back. I did not do that for the new antennas.
I think that adjusting the loading resistors is more important than the
transformer. Interestingly, with the two identical antennas, I got two
different resistor values. One was 1200 Ohms while the other one was 1000
Ohms. Perhaps the ground below them was different. (One was closer to the
water than the other.)
George,
AA7JV
On Wed, 31 Jan 2018 19:19:59 -0800
"Richard (Rick) Karlquist" <richard@karlquist.com> wrote:
I recently built a 70 foot long 35 foot high DHDL that can be pointed east or
west by reversing the feed/termination. I tested it in recent
160 meter contests either west to JA or east to the US East Coast.
The comparison RX antenna was a low full size 160 meter inverted vee
with the apex at 40 feet.
The DHDL didn't exhibit any advantage to JA, and only exhibited
advantage to the east coast with a small number of stations.
When it did have an advantage, it sounded like 3 or 4 dB as the
100 degree lobe width would indicate. It modeled very well on
EZNEC.
It was fed using a 16:1 impedance ratio "binocular" core balun transformer. It
appeared to be in good working order based on it being very deaf to the north and west
when aimed east. This is in comparison to the low inverted vee which is basically
omnidirectional.
The DHDL experience reminded me of my attempts to build beverages
over my high conductivity ground. A JA beverage was very deaf
to the USA, but didn't make JA pop out of the noise vs a low dipole
or even the TX vertical.
Can anyone share their experience with this design. It is possible
I am doing something wrong? What is a better design to try? I
should mention that I have 20 acres available, so I can go as big
as necessary.
73
Rick N6RK
On 1/31/2018 5:52 PM, GEORGE WALLNER wrote:
I was out in the Bahamas for the CQWW160 contest from C6AGU. Both before and
after the contest I got up to work JA-s at sunrise. There was definite peak in
signals. The peaks started just at sunrise (06:47 local time) and lasted about
15 minutes. By 07:15 there was nothing on the band. It was similar during the
contest.
On Monday morning I was testing a new 80 meter antenna. The peak was very
prominent on this band. I was working JA-s from about 06:15 and they were
extremely weak (I had a good RX antenna and plenty of pre-amp gain). Starting
just after sunrise, around 07:00 signals came up to S9 withing minutes. I
worked about 30 stations and most of them were loud. The peak ended very
quickly: I was barely able to complete the last QSO. By 07:20 there was
absolutely nothing.
73,
George,
AA7JV/C6AGU
On Wed, 31 Jan 2018 15:31:14 -0500
Guy Olinger K2AV <k2av.guy@gmail.com> wrote:
I actually wasn't hearing band peaks either, until I got to thinking about
that, and went digging in the RBN stats. The peaks are there. So what gives?
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