Jim, have you considered switching the reflector to a director for long
path? Sounds like your stub switch might allow that.
73,
K5GW
In a message dated 2/21/2015 5:20:47 P.M. Central Standard Time,
jim@audiosystemsgroup.com writes:
On Sat,2/21/2015 12:51 PM, Rick Stealey wrote:
> Yes, but you are comparing your dipole with the same dipole plus
reflector.
No. I did that a year ago when I first rigged the reflector. This
morning, I was using the antenna as a dipole on long path. I had
achieved a 2 dB improvement by raising the antenna from about 115 ft to
about 135 ft.
I raised both wires in the last few weeks. That increased height also
helped it by 2 dB.
This does, of course, clearly illustrate the value of a few dB here and
another few dB there adding up. When I first rigged those high dipoles,
I was feeding them with much smaller coax -- RG59, I think. Modeling
(using TLW, which comes with the ARRL Antenna Book) showed that I could
gain another dB or so by using a good RG11 -- I got a good deal on a big
spool of Belden 8213 and used that. I chose RG11 because it had less
loss due to mismatch at the band edges, because the high dipole is a
better match to 75 ohms.
> Have you considered how to make meaningful measurements on your array?
Say, to determine the frequency of best f/b?
No. Can you suggest a method that doesn't require a drone with
instrumentation? :)
> I think you also have a Steppir. How do you know it is tuned on each
band for the best performance? (the three models that are programmed into
the controller for each band).
I've never taken the time to investigate that. I could, if I wanted to
take the time, plot its pattern by recording field strength as I rotate
it, but that wouldn't tell me the gain. And when I've thought of doing
that, more pressing issues have always gotten in the way -- anything
from repairing gear, to repairing storm damage to antennas, to upgrading
the shack, to improving the antenna system, to making the XYL happy.
Modeling with software like NEC is pretty accurate when properly used.
Some studies I've done show the value of raising a horizontal antenna to
improve the vertical pattern, putting more field stength at low angles.
In addition to getting the 80/40 dipoles (and the reflector) higher, I
also moved my 30M dipoles from about 35 ft to about 100 ft. They also
play a LOT better. A few days ago, I worked a C5 on 30M. He was a lot
louder on the new antenna than the older lower one (which is still
there, for comparison). You can see my work at k9yc.com/publish.htm
Download the slides (pdf) about antenna planning for small stations.
73, Jim K9YC
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