Topband: 1000 feet 5/8" hardline or 600ohm True Ladder line.

[Richard (Rick) Karlquist]

On 4/29/2014 11:28 AM, Jim Brown wrote:

>> Paralleling two
>> runs of line does not decrease the insertion loss.
>
> That depends. Given the same source and load Z as with the single run,
> it does decrease the loss, because the current divides between the two
> lines. The condition that does not reduce the loss is the use of two

> 73, Jim K9YC
>

If a run of 75 ohm coax has 0.4 dB loss in a 75 ohm system,
then a parallel run of two 75 ohm lines will have the same
0.4 dB loss in a 37.5 ohm system.  That's the basic principle.
So the loss of Milt's parallel lines in a 37.5 ohm system
should be the same as what the book gives for one line in a 75 ohm 
system, which is 0.4 dB for 400 feet in the antenna book I looked
at.

Now if you use a 75 ohm line in a 37.5 ohm system, then that
will have more loss than two 75 ohm lines in parallel in a
37.5 ohm system.  That's true but is kind of a corner case.

Rick N6RK