[K3PZN-List] Lightning, antennas, and coax

[Philip Karras]

Kyle,

OK, I see that Andy has taken a crack at beginning your education on impedance and I think he's done a better job than I would have done. So all I'll do it tell you to do your research on the web. Here's a good link I came across to help to learn a bit more:

http://www.wisegeek.org/what-is-impedance.htm

While this talks about 50 or 60 Hz remember we're dealing with anything from 1.6 to ~ 450 MHz. You're not yet dealing with stuff in the GHz range are you?

Anyway, the bottom line is "you can't get thee from here" Meaning, you can't measure the impedance of the coax with an Ohm-meter. I believe one or both of my antenna analyzers can do this BUT, at this point in time I do not believe you need to worry about the impedance of your coax. Don't waste time trying to measure it. As long as the resistance is low for both the center wire and the shield you're probably OK. You're resistance of < 1 Ohm for the run of coax is good. 

I've never seen a coax that has changed its impedance, resistance, yes, but then I've never even tried to measure a piece of coax's impedance, has anyone? I'm not that experienced in this area, perhaps Andy has seen/done this?

While you are at it you also need to know the difference between Watts and Volt-Amps. Yes, Volts * Amps = Watts, but in an AC circuit that has phase differences, as Andy explained about impedance due to AC voltages, Volt-Amps is a similar measure of AC Watts having phase differences. Old linear power supplies were measured only in Watts but today, with switching supplies, perhaps a better measure is the Volt-Amp - most UPS' list both the watts and the Volt-Amps they can handle.

73 de KE3FL,
Phil
AEC Carroll County OES, ORS, & VEARRL Life Member
http://cs.yrex.com/ke3fl
Karras' Corner: http://cs.yrex.com/ke3fl/KarrasCorner.htm