On 7/5/2015 12:10 PM, rickman wrote:
On 7/5/2015 10:48 AM, Ralph Mowery wrote:
"Ian Jackson" wrote in message
...
class-C PAs supposed to be around 66.%?). Also, as much power would be
dissipated in the PA stage as in the load.

I think this is easy to disprove in practice. I have an amp that is
probably class B, but it does not mater about the class. If I adjust
it to
an input of 2000 watts from the DC power supply, I get out 1200 watts
to a
resistive dummy load. If the above is true, I should have to input 2400
watts to the final stage. Now can someone tell me where the extra 400
watts
are comming from ? This 400 extra watts is not even counting on any
loss in
the circuits.

The idea of matched impedance transferring maximum power is one of those
"simplified" descriptions that has preconditions that some people forget
about. It is not a universal truth.

If you have a transmitter output with a fixed impedance you can get
maximum power transferred to the feed line by matching the feed line
impedance to the transmitter output impedance. But if your feed line
impedance is the constant, you get maximum power transfer by minimizing
the transmitter output impedance, meaning zero ohms.

So you could in theory get 1200 watts into your feed line while drawing
only 1200 watts from the power supply.


So why don't manufacturers design transmitters with 1 ohm output
impedance, Rick? Hint: Sophomore-level AC Circuits course in virtually
any EE degree, and anyone claiming an EE degree should be able to tell why.

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