R: R: [antennaware] Feeding cable lenght

K4SB k4sb@mindspring.com
Wed, 04 Aug 1999 00:57:00 +0100

Maurizio Panicara wrote:
> Already you got the answer by Serge, if into the line there
> is an High SWR (like in the well known 1:4 coaxial balun)
> and if the line is long this can be a considerable amount
> of extra losses added.
> I can also add that much less than 1:12 SWR is enough to
> rise coaxial lines losses while open wires are much less
> subject to this effect.
> 73,
> Mauri I4JMY
Mauri and Serge

I have replied to Serge. Both your statements are incorrect. I
totally agree that a 12:1 SWR would introduce excessive loss, but
that condition does not come into play. Remember, we are
discussing 2 and ONLY 2 points on the line, the input end and the
output end. If the load of the antenna is 200 ohms, and you use a
4:1 balun, then 50 ohms will appear at the input of the balun,
and 50 ohms will appear at the transmitter end. The only loss in
the line is its inherent db loss per 100 or whatever feet.

If the load is 600 ohms, and you use 50 ohm coax, the input (Tx)
end will show 600 ohms. Again, the law is that an electrical half
wave of ANY impedence will repeat the load resistance at its


FAQ on WWW:               http://www.contesting.com/antennaware-faq.html
Submissions:              antennaware@contesting.com
Administrative requests:  antennaware-REQUEST@contesting.com
Problems:                 owner-antennaware@contesting.com