On 5/31/2011 6:30 PM, Jim Lux wrote:
On 5/31/2011 4:12 PM, John S wrote:

Are you feeding this with coax? Why not use a big choke at the feedpoint
on the outside of the coax (i.e. a bunch of suitable ferrite toroids)?

I don't understand. The built-in inherent balun needs no choke.


But doesn't it need an extra length of coax on one of the sides?


No. The left-hand side is #14 wire while the right-hand side is coax
(obviously left and right can be reversed). A BNC female is at the
bottom, bayonets downward, terminals upward.

o
/ \
/ \
/ \
/ \
+ +
\ /
\ /
\ /
\ /
oo

The coax (right side) is connected as usual to the BNC and bent as
shown. However, the coax's center conductor *only* is connected at the
top to the #14 wire on the left of the diamond. The bottom end of the
#14 wire is connected to the BNC connector shell at the bottom.

The piece of coax on the right forms the balun. It is close to 1/4W
internally considering the velocity factor of the coax, but about 1/2W
externally.

As I said, it isn't exact. It measures very well here. I measured VSWR
of 1.02 but that was not the important part of all this. I have yet to
measure current on the transmission line from the BNC to the source to
my satisfaction.

If I can supply clarifying info, let me know.

73,
John