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 _______________________________________________ Elecraft mailing list Post to: Elecraft@mailman.qth.net You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com _______________________________________________ Elecraft mailing list Post to: Elecraft@mailman.qth.net You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com
