[Elecraft] KW Twin Lead

[W B Reese]

Dear Jim,

How I have wished for some KW twinlead down the years!

That said, the first thing I would do is check it for efficiency.  Remember 
it is low impedance, and like coax, there is the possibility that it has 
become lossy.

If it passes the loss test, then yes, I think it would be a great idea to 
use it.

How much space do you have for your dipole?

I have about 92 feet of horizontal space for mine and the ends are about 15 
feet high with 4-each 2"x2" poles supporting it along its length.  The ends 
zig-zag down on the ends at an angle so that if viewed from above the 
antenna looks like an "S."  The whole dipole is 160 feet long and is 
resonant on 160 meters.  I use a current balun to feed it and enjoy a low 
SWR on all bands except 12 & 17 Meters (or a portion thereof!) and it is 
very nice to feed with the K2/100-KAT rig.  No rf in the shack etc.  Of 
course this is not a DX antenna!  Anyway, it is a Unadilla with six or 
seven traps on each side, the maximum number.

You might think about the Unadillas, I'm happy with mine and if you use all 
the traps it gives a very substantial loading effect.  Of course, this 
doesn't get the antenna up in the air, but it does get you on the air.

Good Luck,

TR WB6TMY
S/N 0838

At 07:42 PM 1/13/2004 -0600, you wrote:
>I've got most of a spool of some old Belden 8210 72 ohm transmitting
>twin lead that I've had in my basement for quite a few years. It's
>discontinued, and  I can't find any data for it. Can anyone tell me
>anything about this stuff?  It looks to be about #12 stranded copper
>with a mostly foam dielectric, and I suspect that it's rated close to a
>KW on HF.  The oldest copy of the ARRL antenna book in my shack (1949)
>lists a KW twin lead, but without a part number, and shows loss on the
>order of 0.5 dB at 7 MHz, 1.4 dB at 28 MHz.
>
>I'm thinking about using some of this to feed an 80/40 trap dipole so
>that I can put the balun in the shack, not at the antenna. I'm hoping
>that I can then load it more effectively as a random end fed wire  (or
>even as a shot dipole) on 160. The feedline will be on the order of
>60-70 feet long. Any thoughts on any of this?
>
>Jim K9YC