NEC-LIST: Including lossy coax in a simulation model

A tip to MULTINEC users:

NEC-2:s TL facility for transmission lines only provides for lossless lines,
which can be a drawback when trying to study various coax dipoles and
"magic" antennas like the W5GI antenna, which all incorporate shorted stubs
of coaxial cable in the antenna structure.

As MULTINEC is a worksheet in Excel it is not too difficult to represent a
shorted lossy coax stub as a variable R+jX load using Excel worksheet
expressions for the formulas

R = Re[tanh(alfa + j*beta)]
X = Im[tanh(alfa + j*beta)],

where alfa + j*beta is the propagation constant of the coaxial cable. Alfa
and beta can easily be calculated using the loss factor, velocity factor,
frequency and physical length of the cable.

For an open lossy stub the equations are

R = Re[coth(alfa + j*beta)]
X = Im[coth(alfa + j*beta)]

73 Jan/SM0AQW

-- 
The NEC-List mailing list <nec-list_at_gweep.ca>
http://www.gweep.ca/mailman/listinfo.cgi/nec-list