[Elecraft] Final Amplifier Class

[N2EY at aol.com]

In a message dated 9/1/07 8:07:53 PM Eastern Daylight Time, 
john at johnhuggins.com writes:


> Some are suggesting the less than 180° Class C amplification method is 
> what CBs use.  I understand this requires a good tank circuit to 
> complete the sine waves, but is supposedly inappropriate for amplitude 
> style modulations like AM, DSB and SSB.

It depends.

Modes like DSB and SSB are usually generated at a low level at a fixed 
frequency, then heterodyned and amplified to the operating frequency. All stages in 
such a transmitter must be linear, which means Class A, AB, or B. Class C is 
right out because it's not linear.

AM is different.

Some AM rigs generate the signal in a manner similar to DSB or SSB, and in 
such cases the stages must be linear.

But AM can also be generated by modulating the final stage of the 
transmitter. In such "high level" modulation schemes, the final stage does not have to be 
linear, and is almost always Class C. Look at amateur AM transmitters such as 
the EFJohnson and Heathkit for examples of how this was done.

73 de Jim, N2EY


**************************************
 Get a sneak peek of the 
all-new AOL at http://discover.aol.com/memed/aolcom30tour