[TowerTalk] RE: [Antennas] loax 'sweet lenght'

[David Robbins K1TTT]

> 
> ----- Original Message -----
> From: "Joe Subich, K4IK" <k4ik at subich.com>
> 
> > ... however, if one is using 75 Ohm cable in a 50 Ohm
> > system (e.g., CATV hardline) then the multiple of 1/2 wavelength
> > shows a 1:1 SWR on a 50 Ohm bridge - exactly what is desired.
> >
> > The 75 Ohm cable is operating with a 1.15:1 SWR
> 
> What happens to the swr and feedpoint impedance at the transmitter if
a
> RESONANT dipole is fed with ladder line?
> 
> Because there is no reactance at the antenna, I presume there is no
> reactance at the transmitter end regardless of line length?

Wrong, if there is a mismatch at the antenna you can get reactance along
the line that varies in sign and magnitude. 

> 
> However, does the resistance get tranformed--possibly putting it out
of
> range of solid state finals?

Possibly, but of course as I said above you also have the reactance
there also.

> 
> How much effect will rain on the line and imbalance of each side of
the
> line to nearby objects have on the resistance or introduce
> reactance?

Hard to guess.  Rain would probably increase loss which would reduce
effects of antenna mismatch.  Nearby objects could have all kinds of
different effects depending on location and size.