On Mon, 5 Dec 2005 14:02:03 -0600, "RB"
wrote:

Oooopss----I meant coax fed.


If you're really going to feed the antenna with coax, why do you need
a balun? Just run the coax straight to your tuner coax connection.

You're losses on various bands may be pretty high with coax. That's
why most all-banders are fed with ladderline. Losses are lower. But
that's your choice.

Bob
k5qwg

Bob Miller wrote:
You're losses on various bands may be pretty high with coax. That's
why most all-banders are fed with ladderline. Losses are lower. But
that's your choice.

Owen has a feedline loss calculator at: http://www.vk1od.net/tl/tllce.php
EZNEC (including the free demo version at www.eznec.com) can be used
to estimate the SWR to plug into the calculator.

For instance, 100 feet of RG-58a used on 14 MHz with an average SWR of 5:1,
loses ~4.7 dB, or ~66%.

To get the same loss with Wireman #554 ladder-line, the average SWR could
be allowed to equal 53:1.
--
73, Cecil http://www.qsl.net/w5dxp

Bob Miller wrote:

On Mon, 5 Dec 2005 14:02:03 -0600, "RB"
wrote:


Oooopss----I meant coax fed.



If you're really going to feed the antenna with coax, why do you need
a balun? Just run the coax straight to your tuner coax connection.

Sometimes an antenna needs matched to the coax line. An extreme example
is an OCF dipole, which can operate on several bands, but has an
impedence of several hundred ohms. the 4:1 or 6:1 balun will match that
with the 50 ohm coax.


- 73 de Mike KB3EIA -