Frequency range:  25 to 1,000 KHz in three steps - 25 to 200; 100 to 600 and 300 to 1,000 KHz respectively.
Filament battery: 6 volts
Plate voltage: From 60 volt battery
Comment:
1) Six  out of the seven tubes were type V24 and used as high frequency amplifiers.  Type Q valve was the detector.  Widely use in marine work.
2) The model 55D amplifier cost $225 in 1921 as evidenced in a letter from Marconi Wireless of Canada.

Type 55 front view

Type 55 rear view

Type 55 schematic diagram. Download image to enlarge

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Contributors and Credits:

1)  Lewis Bodkin  <05bodkin555(at)gmail.com>
2) Handbook of Technical Instruction for Wireless Telegtaphists
 
 

Mar 7/19