[Elecraft] What about the Zepp antenna?

[Don Wilhelm]

Stuart,

The amateur term 'Zepp fed' does refer to the configuration that you
describe - fed at the end with a balanced line with only one conductor
connected to that antenna.  This is an adaptation of the original Zepp
antenna where the feedline was 1/4 wavelength long and the half wave
radiator was oriented along the same line as the feedline.

If you consider that a half wave radiator fed at the end presents a high
impedance to the feedline, then add a 1/4 wavelength of parallel feedline -
the impedance of the end of that feedline (away from the antenna element) is
low (a 1/4 wave transmission line has the property of inverting the
impedance).  If done properly, the end of that 1/4 wave line could be a good
match for coax (through a current balun) and maintain a low SWR on the coax.

This is not a multiband antenna since the 1/4 wave line becomes multiples of
1/2 wave on harmonics, and it seemed that the original post described a
multiband arrangement.  The amateur 'Zepp fed' antenna could be multiband
with a tuner in the shack, all parallel feedline, and careful pruning of the
feedline length to get it to load on all bands without excessive 'RF in the
shack'

73,
Don W3FPR

----- Original Message -----

| An example of an antenna that does not use a counterpoise, is end fed, and
| half wave long, is the end fed Zepp. (Traditionally fed with a balanced
line
| at the end with only one conductor connected to the antenna.)   Now there
| are some authors such as Moxon who challenge its theory of operation, but
it
| is an old standard antenna in many handbooks, and is never shown with a
| counterpoise, or a better term I have heard, "a driven ground"--   (a
| conductor insulated and used to reduce RF in the shack by providing at
least
| a quarter wave at a given frequency, attached to the common point of
| transmitter. (ground terminal).)
|