Hi again,
Still spending a lot of time to determine which vertical to
add to my "farm". Just learned of the Sommers line.
They are really different!!
Take a look at their "circuit":
http://www.sommerantennas.com/25work.html
This is their page titled Working Principles for the 25 foot
high version. They also have a 50 footer. They claim the
circuit results in a "wave antenna", with a terminating
resistor, a la rhombic style! However, one can replace
the 50 ohm resistor (MFJ dummy load suggested) with
a resonant series circuit to ground back in the shack,
using a second coax back down from the antenna!!
Instead of dumping the power reflected from the
antenna in the load, evidently some of it can be
re-reflected back up and radiated; they suggest
about a 1 dB pick up on 80 and 160 doing this. Using the
usual antenna tuner, with, the input left open, seems to
be what they suggest for this technique.
On the spec page, they give what would appear to be
very credible gain figures vs. dipoles up 1/2 wave.
For example, on 160, they spec gain as down 6
to 8 dB from the high dipole -- that is pretty unusual
to be so direct, I thought. BTW, this on the 50 footer
spec list.
Learning much about different approaches to low band
verticals. Thought you might find this Sommers gadget
interesting.
73, Jim, KH7M
--
FAQ on WWW: http://www.contesting.com/towertalkfaq.html
Submissions: towertalk@contesting.com
Administrative requests: towertalk-REQUEST@contesting.com
Problems: owner-towertalk@contesting.com
Search: http://www.contesting.com/km9p/search
|