[TenTec] OT: coax versus parallel wire

[Dr. Gerald N. Johnson]

On Wed, 2008-06-11 at 15:18 -0700, Jim WA9YSD wrote:
> Years ago I use to use that Rubber twin lead that was used on 
> telephone drop lines.  I was only running 90 watts with a HeathKit 
> DX-60A  I heard but never done it but electrical Zip cord for lamps, 
> I believe was around 75 ohms, some people use to use for lower impedances 
> than 300 ohms.  Desperate times took desperate measures.
> 
>  Keep The Faith, Jim K9TF/WA9YSD
> 
I used to have an 80 meter double extend Zepp in the air. It was made of
#10 copperweld. At various times I used 300 ohm TV flat twinlead,
telephone company spiral bronze strip wrapped direct burial cable, and
1" spaced #18 copperweld (a commercial line). The flat twinlead tended
to have a short life because it had too much of an air foil and with 30
to 50 feet (depending on which year and how tall the center support)
under tension from the antenna to the lightning arrestor, it would flop
in storm breezes (which run an average of maybe 50 mph around this
prairie) an pull the conductor in two. The direct burial stuff was
noticeably stronger, and with its lower impedance made the tuning
different, but I tuned that connection from about 1 MHz to 144 MHz and
made many good contacts with it. The SW support, a large wooden corn
crib took a direct lightning hit and that ended my use of the telephone
cable because it burned the conductors out of it at intervals. Blew up
that lightning arrestor too. Blew a few wooden shingles off the corn
crib. Then I went to the 18 gauge copperweld spaced one inch. It tuned
fine, and I kept it under tension anchoring the bottom end with a rope
tied to  concrete block and to several cross insulators. It didn't catch
the wind, but it didn't survive any motion while encased in ice. But it
wasn't hard to find the broken points (usually it laid in pieces on the
ground) and to splice them back together inserting a few feet of fresh
line to make up for the sections broken in short pieces. I planned to
make a sturdier feed line but haven't gotten around to it and then the
rejected power pole I used to hold up the NW end rotted off at the
ground...  The inverted V I put up wasn't quite as good for my weekly
sked with my dad but it worked OK on a 350 mile path. Needed mostly
straight up radiation anyway.

73, Jerry, K0CQ