View Single Post
  #28   Report Post  
Old March 10th 04, 04:44 AM
Richard Harrison
 
Posts: n/a
Default

Steve Nosko wrote:
"I am missing just what it is that gets to the "Loss-less resistance"
conclusion."

If part of the source resistance were not lossless, efficiency would be
limited to 50%.

Fact is, Class-C amplification frequently is 2/3 or 66.6% efficient.
Twice the power is delivered to the load as is lost in the source.

If we deliver 1000 watts into 50 ohms, we have 224 volts and 4.47 amps
as a load.

Our source is identical,, 224 volts and 4.47 amps. Its volts to amps is
the same ratio, but its loss is not the same power as the power
delivered to the load because part of the source resistance is lossless
because it is the product of interrupted energy delivery, not energy
conversion into heat.

With 2/3 efficiency, when we have 1000 watts into the load, we have 500
watts lost in the source.

500 watts lost means only 1/2 the dissipative resistance as we have
resistance in the load, and thus the source resistance consists of 25
ohms of dissipative resistance and 25 ohms of non-dissipative
resistance. The total source resistance is 50 ohms which matches the
load resistance.

A match allows maximum power transfer.

The less than 360 degrees of energy supplied to the load makes 25 ohms
of dissipationless resistance as a part of our 50-ohm source in our
example.

Keep working on the idea and eventually you may get the model.

Best regards, Richard Harrison, KB5WZI