On Wednesday, June 20, 2012 11:38:42 PM UTC-5, Irv Finkleman wrote:
I was wondering about using a Lecher Wire Feeder in the
shack.
This would allow quick and easy of adjustment of optimum
length for each band.

Please explain further. Lecher wires usually require a short between the two wires and we don't want that. What we need is a way to stretch or shrink the length of the wires, a pair of conductive bungee cords perhaps?

I have seen your switched twin-lead arrangement and it
is still under consideration.

I've tried other configurations like parallel mobile telescoping antennas and copper rods that slip in and out of copper tubing. The switches take no more time than adjusting a tuner and could be automated with a microcomputer and relays.

1. How much radiation would I find in proximity to the
lecher feeder and 300 ohm twin lead. Purely a health
consideration.

Unless the power levels are very high, IMO, a tempest in a teapot. I remember when 11m diathermy machines were all the rage. Balanced transmission line fields tend to cancel a few inches from the wires. I wouldn't grab them - just keep your body organs a foot or so away. I doubt that the RF fields can hurt your hands but that's just my opinion. I've been around RF for 60 years with no ill effects that I am aware of. Of course, RF exposure could be the cause of me being unaware.

Is there a cure for Ham Radio RF overexposure?

It is non-ionizing radiation so most of what to worry about is burning. I'm sure you have burned RF holes in your fingers before. I once burned a hole in my lip from a "hot" metal microphone - still have the scar. I wasn't using a balun on a coax-fed dipole.

2. How much variation in length could I get away
with if I wanted to use a shorter lecher system, or would
I get significant i.e. noticeable benefit by going to the optimum length
for each band?

I still don't understand exactly what you have in mind. If you move taps up and down a Lecher line, you will be leaving an *open circuit stub* attached which will introduce capacitance into the configuration. That capacitance will change the impedance to other than the expected value making it hard to locate a purely resistive current maximum point.

3. How far from your operating position is your
feedline/switching arrangement? Have you noticed
any hair loss since implimenting the system?

I've lost some hair but I am not nearly as bald as my father who was not a ham. My switches were mounted on a piece of plexiglass in a window within reach of my operating position. The switches were on the inside and the loops of ladder-line were on the outside. There's a picture of the plexiglass panel on my web page.

I could set up a G5RV if I fudge a bit

I was once working on a magazine article describing a relay switched all-HF-band G5RV. Someone else said he had submitted such an article for publication so I stopped working on it. I don't remember who it was and have never seen such an article. If one forgoes 30m, the parallel section only needs to be switched between 28' and 38'. I guess I should go back and complete that magazine article. I could envision 10' of copper rod slipping in and out of 10' of copper tubing and controlled from the operating position, something like a screwdriver mobile antenna.
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73, Cecil, w5dxp.com