At 07:27 AM 4/3/02 -0500, Tom Rauch wrote:
> > And think about it. You get the same reflected power for the
> > same
> > incident power if the load resistor is 100 ohms or 25 ohms.
> > Either produces a 2:1 SWR but a 100 ohm resistor would produce 1/4 the
> > current as a 25 ohm resistor. OHM's law still applies.
> > The meter does not precisely measure power for all load
> > conditions
> > but it is real close when the load resistance is close to 50 ohms.
>
>Except for that very last sentence Bill.
I made that statement because the device detects the vector sum of
the voltages generated by both capacitive and inductive coupling. Even
though you may use a perfect square-law detector ( a diode comes close) the
resulting calculation is not proportional to power. I played with the math
for a while and it did not take long to come to that conclusion. However,
with the proper calibration of the meter scale it should be quite accurate
for low SWR's. That is less than 3:1. But I could be in error here.
Generally one uses the instrument with other means to minimize SWR. So in
that sense precision at higher SWR's are not a real concern. I don't have
the spare time to pursue this any further. I will agree that as far as
instruments are concerned it is probably the best standard that any of us
can use or afford.
73
Bill wa4lav
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