RST Engineering wrote:
My bag is VHF, so forgive me if I've bumbled up the calculations. My

numbers show that a standard 108" whip has an input impedance of
somewhere
around 0.04 ohms in series with a 22 pf capacitor.

These numbers are so far from what I normally deal with that I'm not
sure
that I'm right, and I'd appreciate somebody who actually works down
in this
area giving my numbers a reality check.

If they ARE right, how in heaven do most people match to 0.04 ohms?
The 22
pf I can resonate out with a 1 millihenry choke (or thereabouts), but
how do
most people match 50 ohms to fractional ohms in the homebrew arena --
that
is, without just going out and buying a "magical matching box" of
some sort?

Jim
Hi Jim, Your numbers look about right for a 108" whip on 1.8mhz. To
feed a small whip like this you would have to "brute force" it with a
large loading coil at the base. The efficiency will be low and the
bandwidth narrow. To get any efficiency at all, the 2:1 swr bandwidth
will only be around 5khz. Once you tune it up, it will be a single
frequency antenna.
There are things like adding capacitive loading at the top of the
whip, and moving the inductive loading to the center (have to cut the
whip in half). This will make the feedpoint Z a little more managable.
I once loaded an 8' antenna on 160, just to see if I could, but never
got on the air with it. I read somewhere that in the 50's, law
enforcement 2-way radios operated close to our 160m ham band. Wonder
what kind of antennas they used on the police cars. Of course the
distances they were interested in are different from hams.
Gary N4AST