Date of Design The Type 38S  is a modified Type 37S and works in exactly the same way.  It comprised of five parts, with three parts being VALVES and the other two SPARK, one low power/frequency, the other medium power/higher frequency.   The dates of design shown below in the table start in 1924 and finish in 1930, so the overall set can be considered as a 1930 transmitter.
Frequency Range
Transmitter 3Q L/F 3K H/F 3Q Low Power 6D 6F
Frequency range 100-1300 kc/s 5770-26000kc/s 100-1300 kc/s 66-666 kc/s 100-900kc/s
Power supply 2 x 3kW Motor Alternator 2 x 3kW Motor Alternator 2 x 1.25kW Motor Alternators 20 V Battery 2 x 3kW Motor Alternator
Filament supply 1.25kW Alternator 1.25W Alternator  - - -
Valves used 3 3 1 - -
Wave form CW & ICW  ICW ICW Spark Spark
Associated wavemeter 1492B or G9 G13 or G8 & G7 1492B or G9 1492B or G9 1492B or G9
Approximate range in miles 600 World wide at times 100 40 100
Date of design 1924 1930 1924 1929 1930
Power Supply See above to Frequency Range.
Type of Set See above to Frequency Range.
Wave Form See above to Frequency Range.
Method of Producing Oscillations Self
Where used/fitted. Type 38S It is a medium power valve set arranged on many panels.  It is a modified Type 37S and for the most part behaves like it. The modifications are "within" {wholly technical and not operator oriented}.
This set is fitted in the Main W/T Office of Flotilla Leaders.

Other transmitters in the series. Types 38M, 38P.  Again, fitted in 'Leaders only' these sets were multi-facetted, including a mixture of MF, HF and Spark on mains power {one of the Valve sets being Low Power} and a second Spark but on battery or ships 20V low power ring main.  The difference between a Type 38M and 38P was that the 38P had the sophisticated transmitter 4T fitted, and it gave a low power output of only 25W {range 40 miles}, 20V battery supplying motor generator with 600V DC output & a 4V battery for filaments, but it was Master Oscillator controlled and capable of CW, MCW [1kc/s tone] R/T {where approved} from 100-18000 kc/s.  Other than that difference, both sets covered 100-670 kc/s 800-1364 kc/s 3000-20000 kc/s 100-900 kc/s 100-670 kc/s 100-1364 kc/s, CW/ICW/Spark, Self oscillations, with power outputs ranging from 450W to 10W and ranges from 350 miles to 12 miles.

Associated Wavemeter See above to Frequency Range.
Small Schematic

38S L/F Transmitter

Picture below of the Low Power set also tells one about the other transmitters being identical to those in the Type 37S set.


See Type 37S