Hi folks:
The burning question for me this week is how
to calculate the feed point impedance of dipoles.
#1 Assuming free space, #12 wire and less that
half wave dipole, what would be the formula for
calculating the R and X at the center when the
percent of wavelength is known. And along with this
answer a length of open wire line will be brought
down to a feed point to get rid of the X value. I
know that the down line length plus one leg length of
the dipole must equal an electrical 1/4 wavelength in
order to represent a non reactive feed point. I also
know that as the dipole is made shorter and the feed
line longer to achieve this, that the feed impedance
will get lower.
I guess, what I'm really asking is, "what is
the formula for the feed resistance, as a function of
feed line length to antenna leg length, when the
total electrical length is equivalent to a 1/2 wave
dipole".
#2 Assuming free space and #12 wires, what would
be the feed point Z of a full wave dipole or double
ZEPP antenna? I know it is very high in the neighbor
hood of 6000 to 10000 ohms.
I know I can do this by trial and error but
it nice to know the answers.
73, John, WA5BXO
