{Note: I tried posting this yesterday but Charter's NNTP server was having
problems.}

"Hal Rosser" wrote in message
. ..

I think if you're using an older transmitter - keep up the retro theme by
boiling the wood spacers in parafin like the old book says. (But I would
bake them at 190degrees for an hour to remove all moisture first.)

I would also be tempted (considering your home-making the feed line
anyway) to try what I recall being called "G-line", where on the
transmitter end of the line you keep increasing the spacing then just drop
one line - and you have only one conductor going up. then of course, you
do the same thing at the antenna end, going from 2-conductor wide spacing
to 'normal spacing'.

G-line, more correctly known as Goubau line, is not practical for use in the
HF range. It is generally limited to UHF frequencies and above due to the
physical size of the "launchers" which generate a surface wave along the
line. For details, see: Geog Goubau, "Surface waves and their Application
to Transmission Lines," Journal of Applied Physics, Volume 21, Nov. (1950).

What I believe Hal is talking about was the early practice of using a single
wire from the transmitter to connect to an essentially horizontal antenna.
Of course that single wire did not behave as a transmission line, but rather
became part of the antenna working against ground. In many cases this wire
became the actual antenna with the horizontal portion acting as capacitive
loading. The resulting antenna pattern is often quite distorted from that
expected of the dipole. A good ground is needed on the transmitter, yet
problems of RF in the shack are common.

If you do decide to use wood spacers, acrylic urethane varnish applied to
dry wood will last the longest and have the best ultraviolet resistance.
Shellac, a natural product, actually has a surprisingly good ultraviolet
resistance too. While boiling the wood in paraffin wax is authentic, be
very careful as Roy, W7EL, points out. The flash point of typical paraffin
wax is approximately 380 to 390 F. Use a double boiler with water in the
lower boiler to melt the wax keeping it well below the flash temperature.
Be very careful as the hot wax causes very bad burns. Work outdoors and
keep a fire extinguisher handy. If you have a local source of bamboo,
consider using it as it is light and often free.

I have made open wire line using poly(ethylene terephthalate) tensile test
bars liberated from the trash where I worked. These PET "dog biscuits"
worked well in this application as PET has good resistance to UV and is
extremely tough.

73, Barry WA4VZQ