Buck wrote:
I have read several articles that show how this antenna works. The
450 ohm twin lead matches the antenna by wavelength (or some fraction
thereof.) I am wondering if this same concept can be successfully
used with 300 ohm tv twin lead.

The 450 ohm ladder-line yields a 50 ohm SWR lower than 2:1 for all
SWRs on the 450 ohm line between 4.5:1 and 18:1. Most 450 ohm SWRs
fall into that range.

The 300 ohm twinlead yields a 50 ohm SWR lower than 2:1 for all
SWRs on the 300 ohm line between 3:1 and 12:1. So you can see that
the matching range is not as wide with 300 ohm line as with 450
ohm line.

600 ohm open-wire line yields a 50 ohm SWR lower than 2:1 for all
SWRs on the 600 ohm line between 6:1 and 24:1 so that range is
even wider.

It would be interesting to know if some small contraption could be
made to carry one around for a portable operation successfully.

I carry around 1, 2, 4, 8, & 16 foot lengths of 450 ohm line and
just plug them together with banana plugs to achieve a match
without a tuner.

Side-by-side coax can be used as balanced line. I often toyed with
the idea of having a box of side-by-side RG-62 coax (Z0=186 ohms)
connected to switches or relays. For 186 ohm feedline, any SWR
between 1.86:1 and 7.44:1 would yield a 50 ohm SWR of less than
2:1. But you can see the matching range would be pretty small.
--
73, Cecil http://www.qsl.net/w5dxp

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