Ted,
You didn't specify what's the GAP antenna model in question.
Gap (the model I've seen) and F12 Sigma verticals are different antennas.
F12 is a capacitively loaded symmetrical vertical dipole.
Gap is instead a non symmetrical radiator, a short vertical with radials
where the fed point is elevated from the base.
Althoug Rr of the vertical doesn't change at all as Gap claims (what changes
is only the fed point impedance) a conventional balun is not generally
required in this case.
It's a good idea to use a choke balun if radials are elevated, and this is
true with any vertical with elevated radials (at any frequency) to prevent
common mode currents along the coax.
73,
Mauri I4JMY
----- Original Message -----
From: "Ted Bohrer" <N7QY@arrl.net>
To: <antennaware@contesting.com>
Sent: Thursday, May 22, 2003 8:34 AM
Subject: [Antennaware] GAP vertical
> Can anyone direct me to an answer about the GAP vertical?
> It is center-fed, which seems like it might act like a vertical
> dipole, a la the Force 12 Sigma-5.
> But GAP does not mention a balun for it, so how does one use an
> unbalanced coax on a balanced load?
>
> 73 Ted N7QY
> --
> "What could possibly go wrong?" Laurel and Hardy
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