[Elecraft] Final Amplifier Class

[John Huggins]

Yes the handbooks are the place to go and I will sit with one tonight to 
"reboot."  A splendid suggestion thanks.

The information on what modern Ham Transceivers (like the K2 and K3) do 
is also very handy.  Thanks for that too.

John

Gazdzinski, Brett J (Brett) wrote:

>On AM, most CB sets, if not all, use class c in the final,
>(single device), and collector modulate it with a push pull
>class b modulator.
>
>Look up plate modulation, same thing but with tubes.
>
>You use class C on FM, and class ab1, ab2, or class b
>on ssb.
>
>
>Most modern ham rigs if not all use low level modulation
>on AM, like ssb but with both sidebands and a carrier, and
>amplify it like ssb, but with a much higher duty cycle.
>
>Class C can only be used with CW,  FM or plate/collector modulation
>AM.
>
>SSB amplifiers (and AM amps) can be class B, AB1, or AB2, or A.
>
>Class A is VERY inefficient!
>
>All this stuff and more is in the  handbooks.
>
>Brett
>N2DTS
>
>
>
>
>Ladies and Gentlemen,
>
>I frequently contribute technical knowhow to a CB trucker's forum 
>(before you press delete please read on).  The question came up 
>concerning my assertion the single final transistor amplifier, typical 
>in CB transmitter output circuits, operates as a Class A amplifier since 
>the modulation required is AM and sometimes SSB, both being amplitude 
>style modulations, and both desiring of good linearity in the 
>amplification (at least I think so).
>
>I know for sure CB output circuits are not push pull since they have 
>only one power amplifying transistor.
>
>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.  Various resources suggest Class 
>C is fine for CW and FM.
>
>I am sure by now you are saying "That's interesting John, really, but 
>what does this have to do with Elecraft?"
>
>Well, I suddenly remembered some advertisement for an HF Ham Transceiver 
>that offered Class A mode in its output circuit for some improvement in 
>some parameter.  Funny thing is I guess I thought Ham Transceivers 
>always used either Class A with a single device or, perhaps, Class AB or 
>B in a push-pull arrangement.
>
>What I need to know from Elecraft and/or any of you is:
>
>- What is the final amplifier class (A, AB, B or C) used in, say, the 
>KX1, K2 or K3?
>- Is it actually possible to use Class C with an amplitude modulation 
>scheme like AM, DSB and/or SSB?
>- Is the final amplifer in the KPA100 Class A?
>- Do most Ham Transmitters utilize pairs of power devices in a Class AB 
>or B in a push-pull arrangement?
>
>Hopefully this will fine tune my EE knowledge of circuits and make sure 
>I have not missed something I should know so I can continue to represent 
>the ham community well when offering advice to the other radio groups.
>
>Thanks for your help.
>
>John
>KX4O
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