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September 7th 04, 01:24 AM

On Mon, 6 Sep 2004 17:49:00 -0500, (Richard
Harrison) wrote:

It`s true that a parallel resonant circuit constructed of ideal
inductance and capacitance has high (infinite) impedance and no loss.

Actually, if it were isolated in museum glass case perhaps, but the
loaded Q, by design, is less than 20, often less than 10, and in the
case illustrated by Mendenhall's FM transmitter = 2. Loss comes to it
by nature as a practical necessity of moving power (transmitting) to
the Ã¦ther.

The configuration of the high impedance in series with the load limits
output. But, we use imperfect components and we seek a limiting
impedance equat to the 50-ohm load, not an infinite impedance.

The impedance transform of coupling that changed from plate resistance
to load resistance is quite capable of reciprocal transformation (at
least in the rigs of transistor persuasion) to allow return power from
load Z to match towards the source Z. This is the natural progression
of linear design.

My take on the non-dissipative impedance is that it comes from the
switched-off time of the Class B and C amps. During this time in each
cycle, no current flows through the amp to cause loss. Likewise, there
is no current from the amp (actually it is a switch operating on and off
at a radio frequency) to the load or tank circuit. The tank circuit
cleans up the pulse mess, filling gaps in the RF cycle.

By the nature of reciprocity, loss must follow from reflected power
returning through it to a known dissipater, the cathode-plate. If
that cathode-plate is available only intermittently during cycles,
reciprocity is fully functioning through the same available flywheel
of this loaded Tank.

All should notice that if this scenario is NOT working as described,
the caloric demands of reflected power would resolve in a high energy
arc along the way (no one has ever experienced this?). This may
displace WHERE the dissipation occurs, but it does not render
reflected power an inert concept.

All such descriptions can be described in a bulk component model, it
is still the same heat (only the remote arcing becomes an enigma some
would sweep under the rug).

73's
Richard Clark, KB7QHC

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