I would disagree. Power is reflected in a mismatched transmission line.
Send a short RF pulse down a long transmission line with a mismatch
at the end, and then switch in a 50 ohm load at the source end before
the reflected portion of the pulse has a chance to get back to the source.
The load will dissipate the power in the reflected pulse when it returns
to the source point. If the you sampled the meter drive voltage on the
Bird wattmeter with a scope (the meter movement can't respond fast
enough to read the power in a short pulse), you would see that the
meter drive voltage with the slug set in the reflected power position
was proportional to the intensity (e.g. power) of the reflected pulse.
73 de Mike, W4EF............
----- Original Message -----
From: "Kim Elmore" <elmore@nssl.noaa.gov>
To: "AMPS" <AMPS@contesting.com>
Sent: Thursday, March 28, 2002 9:44 AM
Subject: [Amps] Re: Bird® 43 Manual
> At 11:25 AM 3/28/2002 -0500, you wrote:
> > > No. Watt meters that hams and most engineers use at RF measure either
> > > voltage or Current. They do not measure *power*. Given the voltage
or
> > > current, analog meters use a graphical conversion (called a meter
scale) to
> > > equivalent power given under the assumption of a matched
> > > termination. Digital meters also perform a conversion in firmware.
None
> > > of these devices measure *power*.
> >
> >My example is relevant without the need of the Bird wattmeter. I fully
> >accept the fact that the directional coupler samples RF
> >voltage. I'll respond to you as I did with Steve. Namely, in the
absence
> >of a load on a loss-less line, any and all reflected
> >power is being absorbed by the fixed-impedance source (i.e., broadband
PA).
> >
> >If reflected power is not absorbed by the source, where is absorbed?
> >
> >-Paul, W9AC
>
>
> I believe that the logical flaw in the argument lies in discussing
> reflected *power*. *Power* cannot reflected; only voltage and current are
> reflected. We speak of reflected power merely as a convenience because
the
> meter we're looking at unfortunately has "power" written on it. In truth,
> it should say "voltage," so that we could more easily talk about what's
> really happening. Voltage and current presented to a resistive load,
> together and in phase, result in "power." We speak of "power" being
> transferred down a transmission line, but this power is merely a
construct:
> the only things that we can measure on the transmission line are voltage
> and current.
>
> Kim Elmore, N5OP
>
>
>
> >_______________________________________________
> >Amps mailing list
> >Amps@contesting.com
> >http://lists.contesting.com/mailman/listinfo/amps
>
> Kim Elmore, Ph.D.
> "All of weather is divided into three parts: Yes, No, and Maybe. The
> greatest of these is Maybe" The original Latin appears to be garbled.
>
> _______________________________________________
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>
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