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
_________________
Topband Reflector Archives - http://www.contesting.com/_topband
|