It's not clear why you'd make that assumption.

A transmission line doesn't radiate; a traveling wave antenna does.
The feedpoint impedance of a traveling wave antenna is dictated by both
the termination resistance and by radiation. The characteristic
impedance of a transmission line isn't a function of either.

You can make a transmission line with an arbitrarily high impedance,
although because of the nearly logarithmic relationship between wire
diameter/spacing and Z0, values of more than a few hundred ohms (for
open wire line, and considerably less for coax) become impractical. Of
course, you'd have to go to very low frequencies to make use of very
high Z0 transmission line, to avoid line radiation or, in the case of
coax, propagation of other than TEM waves.

And, just out of curiosity, how would you construct a traveling wave dipole?

Roy Lewallen, W7EL

W5DXP wrote:
Reg Edwards wrote:

The feedpoint impedance of traveling wave antennas is usually about
600-800 ohms according to The ARRL Antenna Book.


Anyway, if you have correctly quoted it, the ARRL Antenna Book is wrong,


What is the maximum Z0 possible with transmission line? Seems that would
be the feedpoint impedance of a traveling wave dipole.

Roy Lewallen wrote:
A transmission line doesn't radiate; a traveling wave antenna does.

The energy flowing in a flat transmission line goes somewhere.
The energy flowing in a traveling wave antenna goes somewhere.
Both systems are flat so they seem similar to me. A terminated
Rhombic radiates and has approximately the same feedpoint impedance
as wide spaced transmission line.

And, just out of curiosity, how would you construct a traveling wave
dipole?

In my head or in real life? A terminated Sloping-V comes to mind.
--
73, Cecil http://www.qsl.net/w5dxp



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