The impedance is independent of frequency, and is characteristic of the cable.
The terminators merely 'look' like an infinitely long bit of cable tacked on the end. So they match the cable, but do not define it.
Which just goes to show how a little knowledge identifies a prat.
The whole point about a cable is that it has distrubited capacitance and inductance, and together they end up looking like an almost perefect resustance over a wide range of freqencies.
Which is precisely why we use it.
Impress the girlfriend: Google 'transmission line theory'
no need. You misquote other enough aleady.,
Correct, full marks that person.
Dave
In message , invalid writes
I snip what isn't relevant to what I'm replying to (sometimes)
Where did I mention sine waves? and what exactly do you mean by "sinewaves inducing impedance "?
I presume you are talking about AC with a DC offset, it's not really relevant to the argument is it?
In message , invalid writes
keep learning grasshopper
Do f*ck off
I like impendance, all we need to do now is to find a meaning for it
When somebody posts an intelligent question and we wait for the impending doom of an IMM reply.
Impendance would be the measurement of time between the original post and the entry into Wonderland.
I suppose we could also apply special meanings of conductance, reluctance etc. in this context.
.andy
To email, substitute .nospam with .gl
In article , Andy Hall writes
You love it really, I can tell . . .
The sooner we get some reluctance into this thread the happier I will be ;-)
I like inpedance and outpedance myself. Less tongue twisting than input impedance and output impedance.
Only for an air dielectric cable.
It also happens to be the Zo for minimum loss when epsilon_r = 2.25, i.e. solid polyethylene dielectric.
Compared to what? The higher the Zo the less the capacitance will be (all other things remaining constant). I suspect 93 ohms was another practical compromise - FWIW I notice it corresponds fairly closely with an outer/inner diameter ratio of 10:1 with a polyethylene dielectric.
Not heard that one before. At one time you could get 70, 72, 75 and 80 ohm coaxes from different manufacturers; then they converged and standardised on 75 ohm.
Its obviously the quality of something about to become
As in 'the impendance of her pregnancy militated an accelerated transit process towards the most proximate maternal unit' etc. etc.
Definitely Pseud Speak for 'shit, I'm popping, get me to the hospital'
I was writing the condensed version :-).
Indeed, it represented the top end impedance value which was practically achievable with co-ax cable. Obviously open wire feeders can exhibit higher impedances.
You could get almost anything - somewhere in the garage is an impedance and size matching device for joining 49 Ohm to 53 Ohm airspaced rigid coax from an old radar (it is co-ax - not waveguide). The convergence on 50 and later 75 ohms was initially driven by the wartime imperative to minimise stock holdings and maximise interoperability. At one point a single Destroyer would have to carry something like 15 cables of impedances which differed only slightly and similar (but not identical) size and role. Each of these required different connectors.
OK, so in SI units, it's the temporal distance between the front door and the maternity unit, and is a measure of contractions/red light.
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