>
> 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
