wrote in message
ups.com...
I searched all over the Internet and many books but just could not
find
a formula or rough number of a wire antenna's impedance (not dipole
or
anything else, just a simple, plain wire). I need this number to
match
my small transmitter's final stage output, about 10mW, at 450MHz.
The
final stage's transistor has fT of 6GHz, and is not unconditionally
stable at 450MHz. So I need to match it using Smith Chart. I know
those
portion of work. But I just don't know the wire's impedance's range,
say, is it in the 50-80 ohms or in the 500-600 ohms range or even
1000-2000 ohms? Right now I do not guess this number right, and my
transmitter seems always oscillating at a wrong frequency. So take
an
example, if I use a wire antenna, say, 22 AWG, spools of solid, and
the
length=wavelength/4, what is its approximate impedance? Thanks.
========================================

It is not clear what impedance you are talking about.

If you are asking what is the Zo impedance of an antenna conductor
considered as a transmission line, then it is -

Zo = 60 * ( Ln( 4 * L / D ) - 1 ) ohms,

where L is length of the conductir, D is its diameter, and Ln is
natural logarithms to base e. L and D are in the same measurement
units.

You have mentioned Smith Charts in your query. Zo is usually in the
region of 300 to 600 ohms for wire antennas. The above formula is
approximate and is good enough for ordinary purposes.
----
Reg.