[Boatanchors] SWEEP TUBES AND FPM 300S

[Robert Nickels]

On 1/10/2016 2:41 PM, John via Boatanchors wrote:
> The industry switched to sweep tubes largely as an economic measure. They
> were very cheap as compared to a heavy duty beam power tube such as the
> 6146.  Some operated at lower plate current which made transformers cheaper.
In addition to John's points, the article "The 6DQ5 as a Linear 
Amplifier" in the October 1959 issue of QST describes how sweep tubes, 
being designed for pulse amplification duty, are better suited as a 
linear amplifier for voice signals (e.g. SSB) than a comparable beam 
power tube.    As the article concludes:  "As a class AB1 linear 
amplifier, the 6DQ5 produces about twice as much power output as a 6146 
at similar linearity and with similar plate voltage.   Sizeable PEP 
output of 53 to 80 watts can be obtained with one tube and a 500 to 700 
volt mobile power supply".

I can imagine the light bulb going on over Herb Johnson's head as he 
read this. because that's exactly what he did in the Swan monobanders 
and in the Swan 240 before other sweep tubes (usually in pairs) came 
into widespread usage in SSB transceivers as well as in many popular 
novice rigs.     The 6DQ5 is my favorite sweep tube!

73, Bob W9RAN