[TenTec] Re: Power Amps, Conuugate, Bruene and Maxwell

[Dr. Gerald N. Johnson, electrical engineer]

All Tentecs require antennas. All antennas require feedlines. All Tentec
transmitters use power transistors or tubes for output devices.

These two explanations are antagonistic. Maxwell ascribes a value, Rp as
a characteristic of the tube when the plate resistance varies over the
cycle from far lower than his Rp to full open (unless class A, then the
plate resistance of the tube only rises quite high, but not open
circuit). Bruene fought with Eimac all his working life about that Rp
being a none existent quantity.

I said, while its not a quantity you can measure with a bridge, its a
handy artifice for designing the output network impedance
transformation. Rp has no physical realization in the active device,
whether gridded vacuum tube, bipolar transistor or FET. All these
operate as time variable resistors connecting portions of the supply
voltage to the output network. The output network exists to provide a
suitable load line for that variable resistor. That load line IS
constant over the cycle. The active device output resistance is NOT.

Maxwell wants to say that the active device is matched so the reflected
wave isn't reflected again. I don't see it that way because the output
resistance of the device varies wildly over the RF cycle. What I see is
that the tuner or Pi network is adjusted to accept the feed line input
impedance, whatever magnitude and phase angle, and to transform it to
the proper load line for the active device. In that process the network
has to absorb stray reactances of the active device and its connections.

73, Jerry, K0CQ

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