[ARC5] AM linear amplification

[Kenneth G. Gordon]

On 20 Dec 2016 at 9:05, AKLDGUY . wrote:

> 
> My BC-AO-230 puts out about 5W and I'm interested in boosting that with a 6146B Class AB1 
> linear amp. The ARRL Handbooks say that AM linear amplification is similar to controlled 
> carrier modulation and caution that efficiency is low, about 33%, but don't give explicit 
> operating conditions.
> 
> I assume that the (6146B) stage cannot at any time be driven to the same output that it is 
> capable of in SSB amplification. That's because with no audio applied, the level of the AM carrier 
> drive must be carefully set so that the tube's plate is dissipating half of its rated dissipation. The 
> application of audio drives the stage to a level where the plate dissipation is approached but not 
> exceeded. This level is far below the SSB PEP input.
> 
> Anyone have any comments?

I have nothing to add. You have about covered it. 

Using any linear amp in AM service requires keeping the plate dissipation at a "reasonable" 
level.

You obviously understand that.

I would expect no more than about 25 watts output from your amp. Still, that is 5X the 
un-amplified output. I think that would be well worth the effort.

Actually, the 807 or 1625 has a slightly greater plate-dissipation rating than the 6146. Some 
books show it as having a PD rating about 5 watts greater than a 6146.

In addition, controlled-carrier modulation has greater AVERAGE efficiency than straight AM, 
because the carrier falls to a much lower level in the absence of modulation, while it 
remains steady for AM.

CC modulation of a 6146 results in around 35 watts output.

Ken W7EKB

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