Jeff, Impedance refers to both R and X, resistance and reactance. Impedance affects all current flow, DC and AC. X affects AC only.
Yes DC is steady state. Guess you can get the simple stuff. No a coax will not function the same at 5 Hz as it does at 2 meters. Evidently you have not had the previledge of working with equipment or engineers that allows one to look at some of these issues. Oh well. 73, ron, n9ee/r >From: Jeff DePolo <[EMAIL PROTECTED]> >Date: 2007/09/02 Sun AM 09:01:03 CDT >To: [email protected] >Subject: RE: RE: RE: RE: RE: RE: Re: Re: RE: [Repeater-Builder] Re: Duplexers > >> >> The question is way off base. No one said one cannot carry >> DC or any other signal on coax. The question was what was >> the impedance of a coax at given frequencies. > >You said coax has a low-frequency cutoff. I'm asking about that >specifically. I didn't ask about about impedance. > >> At DC I can guarantee you RG59 is not 75 Ohms unless you got >> enough to get enough R and this is totally another >> discussion. > >Under steady-state conditions, yes, you'd be right. > >> At DC, I would think you would agree one will not see >> RG59 being 75 Ohm at DC. > >At steady-state DC, there's no such thing as impedance, there's only >resistance. By definition, impedance is the opposition to a varying >electric current, i.e. it only applies when we're talking about AC. > >> The same can be said at 1 Hz or 2 >> Hz or 5 Hz...etc. > >No, it can't. If you had a piece of cable long enough, it would behave the >same way at 5 Hz as would a 100 foot piece of cable on 2m. > >> There is a point at which it starts to >> propergate and does look like 75 Ohms. I think you might >> understand this. > >I'm not trying to rake you over the coals Ron, but I *am* trying to prove a >point: there is no low-frequency cutoff for coaxial cable, period. You may >experience (or even measure) behavior at very low frequencies when the cable >is a small fraction of an electrical wavelength that might make you want to >think otherwise, but it's not due to transmission line theory, math, or >physics breaking down at some low-frequency cutoff. > > --- Jeff > > Ron Wright, N9EE 727-376-6575 MICRO COMPUTER CONCEPTS Owner 146.64 repeater Tampa Bay, FL No tone, all are welcome.
