[Milsurplus] AF4K old and new

[Robert Nickels]

On 8/11/2024 7:11 PM, Bob Camp wrote:
> Unfortunately, the basic design issue is “not enough tubes”.

I agree.   I've had no problem using the small crystals in various 
transmitters - as long as they use a separate modern oscillator stage 
(i.e. a Colpitts,  Clapp, Pierce etc).    The problematic ones for 
crystal current are the power oscillators and regenerative crystal 
oscillators which were used in some early multi-band transmitters 
intended for portable or mobile use.   To keep the number of multiplier 
stages (hence, tubes) down, they drove the oscillator hard to produce 
strong harmonics, so the needed one could be selected with a tuned 
circuit and used to drive the PA grid.   The high crystal current caused 
heating and deformation of the quartz, resulting in  the characteristic 
chirp.   As a piezoelectric material, the final stage is deformation 
past the tensile strength limit of the quartz plate.

73, Bob W9RAN
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