"Richard Clark" wrote in message
...
On Mon, 12 Jun 2006 23:40:19 GMT, "Jerry Martes"
wrote:

I did measure the impedance across a loop of RG 223 with 4 tubes around
the outside. The problem I come up with is my ignorance of *whats
needed*
for adequate decoupling of the balanced antenna from the outside of the
coax.

Hi Jerry,

Just think of the antenna as the "source" and consider its
characteristic Z. Now consider the common mode circuit of the
transmission line and its Z. So often this is an unknown, and if we
were always lucky, it would be a half wave multiple to present a very
high Z indeed. Thus 'twould be the end of the story.

How high is high enough? I offer three values for choking:
3 times antenna Z at a minimum;
5 times is practical;
10 times is lab grade.

So, tell us what those 4 tubes measured?

73's
Richard Clark, KB7QHC

Hi Richard

I have been thinking of the "string of ferrites" as a method of presenting
a high impedance to Conducted currents along the outside of the coax from
the antenna down to the radio. It is clear that a "high impedance" may
actually couple well to the outside of the coax if the length of coax is
some special length that presents a high impedance up to where the choke is
located,
I think I could have saved time if I'd asked you more questions when I was
doing the work of learning about baluns.

I didnt keep any of the data I recorded with any of the coils and
ferrites. It is easy to measure the Z of any high impedance circuit so I
could easily measure choke impedance at 2 meters.

Jerry