> "1. Unless the load VSWR is exactly 1.0, the forward power
> indicated by any directional-coupler-wattmeter exceeds the
> net power delivered to the load.
Look at the reflected power. Subtract the reflected power from
forward, and you have real power delivered to the load (neglecting
the small cable and input circuit losses).
> 2. Because the Henry amp's input is a _nonlinear_ load, for
> which voltage is not proportional to current!, all (simple) bets
> are off!! The load is nonlinear because the grid part of the
> cathode/grid circuit rectifies.
It should not appear that non-linear ahead of the tuned input if the
input has enough Q in the input and if the input is a lowpass with a
low impedance for harmonics at the cathode.
> 3. How a nonlinear load appears to a wattmeter depends strongly
> on the voltage and current waveforms, which are nonsinusoidal
> and which change depending on the length of the transmission
> line and any filters, tuned circuits, impedance-matching, etc., etc.,
> between the exciter and the load (the Henry's cath/grid circuit).
If it looks non-sinusoidal at the meter you are in serious trouble.
> waveforms and do not compute power, really; they use diode rectifiers,
> which tend to respond to peak rather than rms voltage, and so on; and
> they infer approximately what the power _would_ be, were only the
> waveforms sinusoidal."
See above. Also, some of those thoughts are wrong.
For example, all direction couplers I've seen at HF actually
measure both current and voltage, and compare the phase. If they
didn't, they could NOT be directional couplers!!
> Obviously (IMO) a nonsinusoidal reflected wave, very rich in
> harmonics, returns from the Henry's cathode (input) circuit; and
> these harmonics are absorbed or reflected by the Icom
> completely differently depending on whether the Icom's
> antenna tuner is switched in. So the voltage and current
> waveforms delivered to the Henry are very different.
Is this a wild guess based on assumptions and unrelated
measurements, or did someone actually look at the waveform on a
scope??
Rest assured, if the waveform is non-sinusoidal the rig and the
meter will show standing waves.
Of course the very same thing can happen if there are no
harmonics and there actually IS only an impedance mismatch.
The only way you would know is to look at the waveform, or
measure the level of harmonics.
> "1. With the amp biased for CW, I get less or more power than
> you do, with the same 99 W of VFD-indicated drive power,
> depending on whether the antenna tuner _inside_ my exciter is
> switched out or in, respectively. IMO this proves that the Henry's
> grid circuit generates and sends a nonsinusoidal reflection back to
> the exciter.
Doesn't **prove** that at all! You need to measure the harmonics,
or look at it with a scope.
73, Tom W8JI
W8JI@contesting.com
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