[Antennas] Buried ladder line?

[W6jod@aol.com]

Tom:

Interesting problem!

How about making two rigid coax cables out of copper pipe, attaching the 
outers together and calculating the proper size of inner to outer to come up with 
225 to 300 Ohms per coax (assuming you want 450 to 600 Ohms for your balanced 
line) and connect the balanced line at each end.  You could even use a conduit 
bender to make nice sweeps like those used on electrical conduit.  

Not having done the calculations and not having a reference book at hand, I 
can't help on what sizes would have to be used for those impedance levels.  I'm 
really guessing, but the inner could be something like #10 bare copper wire 
and the outer 1 or 1-1/4" copper pipe. Wouldn't have to be too big to handle 
the power and the spacers could be fabricated out of any number of plastics 
although Teflon would be ideal!  Reminds me of the 3-1/8 and 6-1/8" lines we used 
for TV transmission before I retired.  Let us know what you decide!

73,

Norm Hall, W6JOD


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