John,
In general, tribanders with longer elements should be more efficient, and
generally get better reviews by their users. Of the ones you mention, the
TH-2 and TA-32 fit the above criteria, but do not cover 17 and 12 (but may
be quite usable with a tuner). Don't know about Force 12 after the recent
ownership change, but the C-3S is another choice. I've also known a number
of hams with the Cushcraft A-3 tribander on a roof tripod.
Another option is a rotatable dipole, especially if you can get it higher.
Modeling shows that when you go from 25 to 40 feet, a 20M dipole has 2 dB
more gain, with a much lower takeoff angle. This option is especially
attractive if you can get a free old tribander with an intact driven
element! I did this with a CL-33 d.e. some years back; it worked well.
73, Gary
K9AY
>I have been looking at getting a 2 element tribander up on the roof tripod,
>so its height will be about 25 feet or so above ground. The 2 elements
>ones I have seen on the market with a manageable boom length (6 feet or so)
>for me include the Mosley TA32jr, Mini 32, and Mini 33, the Cushcraft MA5B,
>and the Hy-Gain TH2. In looking at the specs of these antennas there seems
>to be some real differences in the advertised gain, in the order or 2 or
>more DB difference on some bands. Has anyone modeled these antennas at a
>low height (or used one at a low height) and could comment on their
>performance or modeled gain?
>
> 73s John AA5JG
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