On Thu, 15 Jan 2004 11:07:39 -0700, "Ken Bessler"
wrote:


"Richard Clark" wrote in message

Hi Ken,

Sounds like Barry wants to sell a BalUn if that is the sense you get.

73's
Richard Clark, KB7QHC

1) If you knew Barry, you would not think that
2) W4RT dosen't sell baluns

The question still stands - would adding a 4:1 balun at
the transition between coax and ladder line improve the
system or is a coax choke good enough?

73's de Ken KG0WX


Hi Ken,

The value of the coax choke is found in its ability to snub common
mode currents. Given the proximity of earth such currents are an
almost certainty - however, suffering from them is arguable. You
haven't complained of it forcing you to use this as a solution have
you? If so, I missed that.

The coax choke does not perform an Z transformation. Do you
anticipate that the antenna will present 200 Ohms to you somewhere
(especially so close to earth)? Does your data support this
expectation (in other words, howcum why a 4:1 BalUn with all the 2:1
SWRs)?

Do you anticipate that the antenna will present 12.5 Ohms to you
somewhere? Does your data support this expectation? (Notice the
parallel development to the question above.) Will you be connecting
this BalUn backwards to support this notion? (Was it even mentioned?)

The sales clerk's suggestion seems mostly gratuitous. Back in the
30's W.C. Fields would have offered "Go away son, you bother me!"

73's
Richard Clark, KB7QHC

The coax choke does not perform an Z transformation.

Hi Richard,
I was wondering about that when I tried to answer Ken's question. The choke
he described was 13 turns of RG-58 on about a 5" form. That is about 17' of 50
ohm coax. That will transform the heck out of impedances other than 50 ohms
resistive.

This implies the coax choke does perform a Z transformation. I think a true
1:1 balun can best be realized with a W2DU type with a 100 or so ferrite beads
on about a foot of coax. What do you think?
73 Gary N4AST

JGBOYLES wrote:
The coax choke does not perform an Z transformation.

I was wondering about that when I tried to answer Ken's question. The choke
he described was 13 turns of RG-58 on about a 5" form. That is about 17' of 50
ohm coax. That will transform the heck out of impedances other than 50 ohms
resistive.

Yep, on 30m that's just about a 1/4WL series section transformer.
--
73, Cecil http://www.qsl.net/w5dxp



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