On 3/17/17 10:39 AM, Jim Brown wrote:
Several observations in pursuit of my ongoing war on using words to
describe things that get in the way of understanding how things work.
(And not intended to be critical of Steve.)
Phase is a continuously valued function and is measured in degrees. It
has meaning ONLY for signals of precisely the same frequency. For any
system where time is a factor, phase is a linear function of frequency
and of time.
What is being discussed in this thread is NOT phase, it is POLARITY.
And so, to return to the original question... how would one determine
the (relative) polarity of a choke/balun/black box, with coax on one
side and two wires/terminals on the other.
Consider it as a transformer (potentially 1:1 turns ratio, but maybe
not, maybe with DC continuity, but maybe not)
with simple (MFJ 259 type) analyzer, DVM, etc.?
(with a VNA or an oscilloscope, it's easy, but say you're up on a tower,
or at field day, or..)
I wonder if there's some unambiguous way to do it, or, alternately, if
there's some proof (in a theoretical sense) that it is impossible to do
with a scalar measurement system.
This is sort of a qualitative test I'm looking for..
It's sort of related to the question of what could you use to do a quick
go/no-go test of a device like this (I suppose you can measure the
impedance looking into the coax with the two other terminals open and
shorted.. there *should* be a difference... if there's not, something is
definitely wrong) a "did it fail", not a "is the loss 0.001dB
different" test.
I remember being at a FD and having just this question.. Hmm, the
antenna seems not to be working right, maybe the balun is fried? Well,
it shows DC conductivity, but I'm not sure that means anything at 14
MHz, etc.
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