[Elecraft] folded dipole of topic

Vic Rosenthal [email protected]
Mon Dec 29 12:08:22 2003


David Schornak wrote:

> does anyone know of a math to design a folded dipole I know the
> length is 468/fMHz but what is the distance between the two wires see
> ya

If the wires are the same diameter, the impedance step up will be 4 
times, regardless of the spacing.  A dipole's impedance varies with the 
height above ground (the ARRL Antenna Book has a chart) so the FD 
impedance will come out from about 200 to 300 ohms.  Note that if you 
use a solid dielectric such as tv twinlead, the velocity factor of the 
line becomes a factor.

If the wires are of different diameters, then the step-up varies 
according to the diameters and the spacing.  Again, the ARRL Antenna 
Book has a chart and formula.  It's slightly complicated, so I don't 
remember it exactly.

-- 
73,
Vic, K2VCO
Fresno CA
http://www.qsl.net/k2vco