While the lumped element match is a viable solution. Here's some info (I
don't see Cecil's response)

The spacing of the ~1/4 wave matching section is not critical - here's
why. First, it can be viewed as nothing more than a section of transmission
line, obviously shorted at the bottom (though this section does not have to
be vertical, it's just convenient in many cases).
The spacing and thickness of the conductors will determine the
characteristic impedance (Z0). Normally the Z0 of T-Line is critical, but
this is a bit of a different situation. You are trying to get a match
between the 50 ohms side and something around 2000-3000 ohms (I'll use 2500)
which is at the bottom end of the (vertical) 1/2 wave antenna. Now, on this
design, we have the "liberty" of connecting the 50 ohm line anywhere we want
on the matching section.
And, second, if you view the resulting impedance along the line as
varying from zero at the bottom (shorted end) to 2500 at the top (antenna
feed point), there certainly will be some location (nearer the short) which
is at or close to 50 ohms.
The higher the Z0 of the matching section, the higher up you'll have to go
to get the best match. I'm pretty sure in is my 1947 handbook (non ARRL)
that has one, but it is wires and a wood frame.

There will be, however, discussion regarding the balanced connection on the
matching section and the unbalanced coax, but I won't go into there. I'm
sure others will...as well as the fact that it doesn't matter which side the
coax center conductor should be connected to (doesn't matter).

You can also do a search on "Arrow Antenna" and see an interesting (and oft
argued) variation that does not use a short at the bottom.

73, Steve, K9DCI


"JIMMIE" wrote in message
oups.com...
Thanks Cecil, I was concerned about spacing of the stub more than
anything else. I guesstimated this should be about a foot. I also know
I could be totally wrong. By looking at some plans the distance between
the short and long tubes seems to vary with the frequency and size of
the tube. Doubt if it is too critical. I downloaded EZNEC a few years
ago and could never figure out how to use it.