You are thinking about the Lattin Antenna -- there's
lots of info available on the net for it. Instead of a dipole,
you could use one half the dipole as a vertical

Irv VE6BP


"Ian Jackson" wrote in message
...
In message , W5DXP
writes
On Friday, June 7, 2013 4:42:13 PM UTC-5, Ian Jackson wrote:
... one side is fed from the TX, and the other side is open circuit.

The 1/4WL folded monopole is resonant with a feedpoint impedance around
three times a 1/4WL single-wire monopole. Those two antennas have
approximately the same gain.

If one disconnects the folded element's ground connection leaving an
open-circuit, the feedpoint reactance becomes extremely high and the
antenna loses about 6dB of gain compared to the standard 1/4WL monopole.
It looks more like a 1/4WL shorted stub than an antenna.

I thought something like that would happen. However, because of the close
coupling between them, you might instinctively think that the two
conductors would still simply act as a single conductor, and the feed
impedance would be low (more like a non-folded monopole).

Can't you make a trapped dipole (or whatever) using 300 twin for each leg,
but with sections of one conductor cut out so you form a succession of
1/4WL shorted stubs (of various lengths) in series, acting as traps on the
various HF bands?
--
Ian