[Elecraft] K3: 630m amplifiers

[Tom Azlin W7SUA]

Interesting discussion, but I'm now confused.

In all the old handbooks the discussion of amplifier design says ( page 
76, 1941) "In amateur transmitters, and r.f. amplifier is invariably 
operated Class C ( see Chaptr 3)." I though the final tuned circuit was 
simply "pulsed" at the RF freq and then the output filtering knocked off 
harmonics leaving a clean CW note. And in the article on construction of 
a 100-175 watt CW transmitter ( page 155-157) the 6L6 crystal oscillator 
was cathode keyed with a bit of RC shaping. Rest of stages powered up 
when in transmit.

And I thought these days some AM broadcast transmitters operated Class 
E. Clearly not linear.

73, tom w7sua

On 7/26/2015 9:32 PM, Alan wrote:
>
>  > CW would be another mode that would not need a linear amp I think.
>
> No, CW requires a linear amplifier.  CW is not constant-amplitude - the
> amplitude changes every time you open or close the key.  A class-C
> amplifier would mess up the key shaping, causing key clicks.
>
> Any true FSK or MSK signal should not be bothered by a non-linear
> amplifier.  The only caveat I can think of is that the amplitude of an
> AFSK signal may have some ripple on it to the extent that the passband
> of the transmit crystal filter is not flat.  But I doubt that's a
> significant issue.
>
> Alan N1AL
>
>
>
> On 07/26/2015 06:57 PM, Tom Azlin W7SUA wrote:
>> Hi Don and Alan,
>>
>> I was thinking one of the slow multi tone FSK modes that are a single
>> tone at a time. WSQ is in the same class.
>>
>> http://www.qsl.net/zl1bpu/SOFT/WSQ.htm
>>
>> CW would be another mode that would not need a linear amp I think.
>>
>> On the other hand PSK31 would require a linear amp.
>>
>> 73, tom w7sua
>>
>> On 7/26/2015 5:43 PM, Alan wrote:
>>> On 07/26/2015 05:32 PM, Don Wilhelm wrote:
>>>
>>>> Soundcard sourced digital modes are really SSB signals and need a
>>>> linear
>>>> amplifier.
>>>
>>> The one exception might be FSK.  It is constant-amplitude so a class C
>>> amplifier should be fine.
>>>
>>> FSK modes include RTTY and I believe WSPR and WSJT.
>>>
>>> Alan N1AL
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