[TowerTalk] COAX LENGTH

[Edward W. Sleight]

Woods, Eric D (edwoods) wrote:
> 
> I think you can do this maybe for one band, but don't depend on the primary
> constants (R, L, G, C) to be non-variable with frequency.  In other words,
> you can reproduce the load impedance with an N X 1/2  wavelength electrical
> feedline at one particular frequency (+/- some kinda bandwidth) but don't
> expect it to do the same thing when you double the frequency.
> 
> Eric, K6GV
> edwoods@pacbell.com
> 
> Here come the Smith - Chart people......
>  ----------
Sorry Eric, but not so. You may use any multiple of an electrical half
wave you want, ( as long as it is an electrical half wave at the lowest
frequency of operation )and it is frequency independent. For example, an
electrical half wave cut for 7 Mhz will exhibit the same characteristics
at 14, 21,28,....ect...

The rule is that an electrical half wave ( or multiple thereof ) will
exhibit the same impedence on end 1 as it sees on end 2, no exceptions.

It will do nothing however, to match a mismatch at it's input end. In
other words, if you've got 33-j100 at the input, you'll see the same
thing at the output.

Can it be I've discovered another "soul mate" regarding the Smith
charts. 

73

Ed

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