zeno wrote:
If one is constructing ladder line, is the point to design the ladder line
so its impedance matches the characteristic impedance of the antenna
itself at its feed point?

The point of using ladder-line is so the antenna impedance doesn't
matter (within reason). SWRs on the ladder-line range up to 30+:1
with small ill effects. A 30:1 SWR on ordinary coax is a signal
killer.

Consider that the feedpoint impedance of an all-HF-band antenna
might range from 60 ohms to 3000+/-j3000 to 6000 ohms. The SWR on
Z0=600 ohm line would be around 10:1. The SWR on Z0=50 ohms would
range up to 100+:1.

The theoretical feed point impedance for a full wave loop antenna is
approximately 100 ohms, (but this does change, and is dependent upon
antenna height above ground, near-by structures, and ground conductivity.)
Should I try to make my ladder line to get as close as possible to this
100 ohm?

Nope, go for simplicity. There's not much practical difference between
Z0=400 ohms and Z0=600 ohms. And you may be able to use the impedance
transforming properties (on a line with reflections) to your advantage.

Anyone think that maybe non-insulated would be a better way to go?

Non-insulated wire allows one to hang parallel stubs up and down the
line, useful for matching purposes. It also allows one to measure
actual feedline voltages.
--
73, Cecil, http://www.qsl.net/w5dxp



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