[Boatanchors] SWEEP TUBES AND FPM 300S

[W4AWM at aol.com]

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. 
They  would last much longer if they were air cooled and tune up periods were 
kept  short which many ignored.  The best way I found to tune a sweep rig,  
especially when tune up periods were extensive due to an antenna tuner, was 
to  keep the drive low until the final seconds of the tune up period.
 
I have three FPMs in the collection, The main weak link in the rig, in  
addition to sweep tubes and slightly unstable VFO was the drive belt.   
Fortunately, a repro belt is readily available.
 
73, 
 
 John, W4AWM