The LPDA Vs F12 Vs Steppir thread begs for some common sense. Each offers a
compromise because most hams can't erect monobanders on separate towers for
each band. So which compromise is better? Depends. (how's that for muddying
I have 4 towers and a number of monobanders (plus 40 years of building
contest stations), so I have points of direct reference.
I have a F-12 EF340D, 3 element 40. It replaced a Cushcraft 402D that was
destroyed when the antenna above it failed and came crashing down. 10' above
40 is a Mosley Classic 33. The EF340D, with the alumi-weld linear loading,
gave K6ZM years of flawless performance in an environment where there was no
snow or ice. It has failed two of the last two winters at my QTH from wind
and ice. I am replacing it with a C39XRN which has F12's newest (and much
heavier duty) linear loading on the 40 meter elements.
Common sense: The stack seemed like a good idea, but the CL33 never really
performed because it is a high-Q trapped antenna too close to the 40m beam. The
40m beam was a killer but wouldn't stay up in our winters. The C39XRN
appears to be the common-sense solution. Stay tuned.
I have a PRO 57B on another tower that is used as a backup antenna and on 17
and 12M. Again, it is a very high Q trapped antenna and is detuned by nearby
Vee beam and other wire antennas. While it is only slightly down in gain from
an optimized 4 el 20 on another tower, it is not meeting my needs due to
erratic SWR changes as I turn it around the wire antennas. I am replacing it
with a Tennadyne T-12 LPDA.
Common sense: While an LPDA is a compromise, it is a low Q antenna and my
expectations are that it will compare favorably with the monobanders and not
the wire antennas. Stay tuned.
I have a F 12 C31XR on yet another tower. It is hard to tell any difference
between it and the 4 element 20 and 5 element 10 monobanders. It made it
through the winter with flying colors and is my main antenna until the others
Common sense: The F-12 multi-monoband design is the least lossy compromise
in conventional yagis. The radical element and boom taper schedules are largely
responsible for their resilience in poor weather.
As for the SteppIR. Don't have one and don't want one, only because I have
been bit in the past buying serial #1. 30 years ago, the Kirk helically wound
fiberglass beam seemed to be the solution to a short 40. Unfortunately, over
time, they did not stand up in weather and UV.
Common sense: SteppIR looks like a great solution, but cautious optimism
needs to prevail until there is several years of survival history in many
different operating environments.
Common sense summary: Read, ask and evaluate your objectives. Try what you
think is best. If it stayed up last winter it wasn't big enough. You can never
be loud enough, that's why summers are made for fixing weather damage and
changing antenna configurations. Enjoy the journey.
Virginia City NV
See: http://www.mscomputer.com for "Self Supporting Towers", "Wireless Weather
Stations", and lot's more. Call Toll Free, 1-800-333-9041 with any questions
and ask for Sherman, W2FLA.
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