I know I'm going to regret stepping into this one, but since when has that
stopped me before...
> Thanks, Gary, for admitting the 43 doesn't measure power
> directly.
What do you mean by "measure power directly"? If you're talking about
comparing a thruline measurement against absorptive/calorimetric techniques,
then that's apples and oranges, one is measuring power in a transmission
line (either with or without reflections present), the other is measuring
power absorbed into a load, big difference.
Please clarify what you mean by "measuring power directly" so at least we're
all on the same page.
> Of course, it is a directional coupler, no argument. That
> makes it a reflectometer
No, it's not a reflectometer, it can't do forward and reverse measurements
concurrently.
> If the meter did as you suggest, then it would show what the
> voltage and current are at any point in the line, and
> therefore be able to tell you what the impedance is at that
> point
Not without knowing the phase between the two it couldn't.
> BTW, my POS Daiwa can show me a 100% reflected condition,
> just like the Bird. And just like the Bird, it doesn't
> indicate if that's an open or a short.
A Bird isn't a VSWR bridge, it's a directional wattmeter. Yes, it can be
used in a roundabout way to measure/calculate VSWR, but it's not a "VSWR
meter".
Sidebar. I grit my teeth when I hear someone on the radio say "my SWR meter
shows I'm putting out 100 watts". Since when does a SWR meter measure
power!???! Do you use your bathroom scale to check your blood pressure?
Egads.
I'm not taking a stance here (at least not yet) on the relative merits of
the Bird 43 or other thruline-type wattmeter line sections or elements, I'm
just trying to get a handle on the matter that is the subject of debate...
--- Jeff WN3A
