As the other posters pointed out, it depends on it's length, where it is
above what kind of ground, and how it is fed. It will be influenced by
stuff around it like aluminum siding, fences, trees, and all sorts of
things. Some of the influences aren't minor, unless they are all
wavelengths away.

If you have an end-fed quarter wave, which I suspect is what you are
describing, then it needs to be fed against something, most likely ground.
In that case, it will be about thirty ohms at resonance, plus the resistance
of your ground, which could be substantial. That assumes "free space", of
course, which isn't bloody likely. More likely you are relatively close to
a less than perfect ground, so the impedance could be almost anything. Even
in a perfect world, with pefect ground, the impedance varies with height
above ground.

It isn't like there is some simple answer that is being kept secret. It is
a complex question, with lots of variables. As one poster pointed out, the
best answer short of measuring it, is to model it with something like EZNEC.

You indicated your objective was to come up with some sort of impedance
transformation from a rig you are building to this antenna. Given the
opportunity for significant reactance, I would suggest you locate someone
locally with an antenna analyzer and measure it! An SWR bridge won't tell
you enough to design the matching circuit; there will be reactance, and a
2:1 SWR says IF it is all resistive, maybe it is 25 ohms, maybe 100. You
have no reason to suspect either and likely there is some reactance so
probably it is neither.

So go measure it!

...

wrote in message
oups.com...
Thank you both above. But as I mentioned, I only wanted to know the
impedance of a simple, plain wire. No dipole, no complex antenna
structure. Please help.