Ken Brown wrote:
>John,
>
>The short answer is: It depends.
>
>Once upon a time it was standard procedure to run the final amplifier in
>an AM transmitter in class C. This works fine when the final amplifier
>is the stage that is modulated. A class B push pull modulator modulates
>the class C final RF amplifier and it produces a good AM signal. This is
>the way that most AM transmitters, both for broadcast and communications
>used to work.
>
>
Ah yes, that is what I forgot. If you modulate the final stage it can
be C, but if the modulation occurs earlier you need linear
amplification. Many thanks for jogging my memory on that simple truth.
>If an earlier low power stage is modulated, then all of the subsequent
>RF amplifier stages need to be linear. They could be class A, class AB,
>maybe even class B (probably not), but absolutely NOT class C. If the
>rig runs SSB as well as AM, then it almost certainly generates the SSB
>at a low level, and does not use a modulated final RF amplifier stage
>even when it is in AM mode. In that case the final RF amp must be
>linear, and is not class C.
>
>
So in the case of external linear amplifiers for ham radio which are be
name and definition linear amps can they be Class AB or B if they have
only one output device (tube) or are they often big hot Class A?
In other words, can Class AB or B use just one tube or transistor (and a
tank circuit) or must they always by a pair for push-pull operation to
achieve the linear response?
>DE N6KB
>
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