[AMPS] SWR and line length, etc.

[Pete Smith]

At the risk of fanning the flames again,  I think the original question was
whether a change in line length could cause the apparent resonant frequency
of an antenna to change. My 20M antenna has a feedpoint impedance of 35-j14
at 14 mhz.  If I mathematically attach a half-wavelength of RG-8 (using
TLA.EXE), the impedance at the input end of the cable becomes 36-j 13.3,
and the result, as you'd expect, is slightly lower SWR due to line loss.
however, if the line is pruned to 1/4 wave, the resulting input-end
impedance is 61.75+j23, and it appears that the antenna has magically moved
from being short at 14 MHz to being long.  The SWR hasn't changed,
fundamentally, but the mix of reactance and resistance confronted by the
AMP sure has, unless I misunderstand what the program is telling me. 


73, Pete Smith N4ZR
n4zr@contesting.com 

Sometimes a tower is just a tower

--
FAQ on WWW:               http://www.contesting.com/ampsfaq.html
Submissions:              amps@contesting.com
Administrative requests:  amps-REQUEST@contesting.com
Problems:                 owner-amps@contesting.com
Search:                   http://www.contesting.com/km9p/search.htm