I have been discussing 40 meter antenna performance with several of you
one on one and I thought it might help to relate some of my 40 meter
antenna experience to the reflector.
Going from a 40 meter dipole to an extended double zepp (two 5/8 wave
wires) was an easy 2 dB gain antenna over the dipole It was. fed with
open wire and my still favorite tuner, the Johnson Matchbox.
Later it was the extended double zepp going to a Mosley 2 element center
loaded beam (Mosley called it a Trap Master, K8MR affectionately called
it a Sucker Master). It had narrow VSWR performance and was only
slightly better than the extended zepp as far as signal gain was
concerned. Then came the KLM 4 ele (short elements) beam. This opened up
a whole new world on 40 even though the beam was on a 70 ft crank up
tower. The front to side ratio of that antenna was marvelous. I was
always fixing the hardware issues on this beam, but when it worked, it
was real good for the low mounting height.
Then the huge upgrade to a full size 3 ele 40 at 190 feet, then the
stack of 3 ele 40s at 190 over 100 feet, then the WA3FET OWA upgrade of
the 3 element antennas to full size 4 element stacked 40 meter beams on
50 ft booms. Both sets of full size antennas, mounted higher above
ground, was another level of gain and pattern improvement.
I also put up a Cushcraft 2 ele beam on another tower at 140 ft high
mounted 800 ft away from the big stack. It is very interesting to
compare the Cushcraft to the 4 over 4 stack that is now mounted at 190
ft over 120 ft (lower antenna raised to improve the directive pattern of
the stack). The Cushcraft was assembled stock without any changes and
through the years the pattern and VSWR deteriorated. Two summers ago I
took the antenna down, cleaned the elements, reapplied new Penetrox and
drilled out the rusted screws that hold the coil ends. I replaced the
screws with threaded #10 stainless bolts and the antenna is as good as
new.
I always heard there were problems with the Hy-Gain linear loaded 40
meter beams, but I never had any direct experience with them.
I know there were a few west coast guys working on high Q coil
replacements for the Cushcraft antenna, but I believe the efficiency
gain would be hard to measure in the real world environment and may not
be worth the cost and effort.
Most of the time my stack is 6 dB better for DX signals when compared to
the Cushcraft. It was a ton of time, money and effort for those 6 dB,
but it pays off in the contests.
I built 4 ele full size antennas copies of what I have up in the air for
K8AZ, K9NS stack of 2, K4JA stack of 2, and NO8D stack of 3, three years
ago. They all report great results.
The value of a 2 ele shortened rotating antenna over dipoles is huge for
DXing and contesting. Pictures of the 4 ele 40 meter antennas are on my
web site.
73,
Tim K3LR
http://www.k3lr.com
|