[TowerTalk] 50:75 ohm transformation

[DavidC]

> Yes, you are quite right if you are operating only on one band.  I use my
coax
> for feeding a triband stack and it needs to be flat across that portion
of the
> spectrum.  Parenthetically, I had a devil of a time getting a respectable
SWR
> with my stack last summer after 3 years of no maintenance.  I finally had
to
> just make everything flat to 50 ohms  with UNUNs, etc. and it finally
started
> behaving.  Before, I just went direct from 50 to 75 ohms and vice versa. 
That
> introduced all kinds of strange impedances back in the shack at different
> frequencies.  73/Mike, N7ML

Local contester KM1H runs 75ohm CATV to all of his HF, VHF and UHF antennas

without UNUNs and says the impedence bump over several hundred foot runs
are 
unnoticable, especially since the loss in such cable is so low.

He also says that he has discovered that many antennas are closer to
60 ohms than 50, so 50 ohm cable also sometimes introduces a mismatch.
He is now building his own long-boom beams for 6 meters so I suppose he 
can optimize those for 75 ohms and have the best of both worlds!

Oh well ... so much to learn ... 73, DavidC  K1YP

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