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Old July 17th 03, 09:57 AM
Richard Harrison
 
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Dr. Slick wrote:
"What does it say?"

I don`t have Kraus, unfortunately.

I do have Arnold B. Bailey`s "TV and Other Receiving Antennas". Bailey
covers more antenna territory than most, and does an excellent job of
it. Bailey also includes a catalog of antenna types, all sized for 200
MHz for easy comparison.

Bailey says the surge impedance of an antenna is inversely proportional
to the capacitance per unit length. Reminds one of a transmission line.
This is non-uniform, so Bailey has an empirical equation which says the
larger the periphery of the rod, ther smaller the average surge
impedance.

The ratio of the electric field to the magnetic field surrounding an
antenna must be related to the ratio of volts to amps in the antenna
wire (the surge impedance).

The surge impedance of a thin-wire 1/2-wave dipole from page 500 is 610
ohms (average).

The surge impedance of a fat-cylinder 1/2-wave dipole from page 502 is
240 ohms (average).

Pattern and gain are identical for both antennas. But, Dr. Slick may be
on to something after all. The bandwidth of the fat antenna is about 3X
that that of the thin. In antennas, bandwidth is often an indicator of
match.

Best regards, Richard Harrison, KB5WZI

 
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