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TYPICAL W/T OFFICE AS FITTED IN A DESTROYER CIRCA 1920s

  This equipment was designed to be worked with only one rating on watch at a time so all controls were within easy reach of the operator.

  The main Transmitter Type 37 was developed in 1924. It operated on frequencies between 100 and 1365 Kc/s with a minimum range of 350 miles. The Right Hand Panel of the Exhibit contained the full wave rectifier using two Glass Rectifying Valves. The Left Hand Panel was th Oscillator section using the Aerial circuit for the frequency determining circuit and a Silicon triode valve. Silica as an envelope was a Naval development for high power valves and this particular example was capable of handling 2.5 kilowatts with 12,000 volts on the anode: the filament took 18.7 amps at 12.5 volts.


Type 4H Tx

For inter-communication with ships in company a low power transmitter 4H was fitted to the left of the main set. This was design in 1925 to cover the frequency range from 375 to 1765 kc/s and ha a range of 10 miles. The transmission was M.C.W. using a valve modulator on 1995 cycles per second in th H.T. lead to the R.F. oscillator.



  The Receiving Equipment consisted of the Model C Tuner Outfit, designed in 1912 and the M3B Amplifier, designed in 1923. Model C was made up of four tuned circuits - Aerial, Acceptor, Rejector and Secondary.





Condenser No.7
  The Aerial included an Aerial Inductance No.5 giving up to 10,000 microhenries via 6 tappings, in series with an Aerial Inductance No.1 which could give practically every microhenry up to 5320 via thre tapped coils, and a No.7 Variable Condenser consisting of 5 fixed capacities could be put in parallel with the No.7 and its value adjusted by knife switches to give up to 16.4 jars capacity.




  The Rejector Circuit was tuned to the same frequency as the wanted signal and used when interference was troublesome, offering a high impedence to the wanted frequency and a low impedance to interference. It consisted of a No.14 condenser similar to the No.13 but giving up to 3187 jars total capacity, a small tapped inductance and a fine tuning inductance (No.12) formed by a rotating contact on a copper strip.


Inductance Mutual Tuner No 41   The Secondary Circuit used the tapped Secondary of the Inductance Tuner Mutual and another No.7 condenser which also had a No.13 to go in parallel with it. Th coupling between Primary and Secondary was adjusted by sliding the Primary relative to the Secondary.

  Amplifier M3B was a general amplifier and detector for the reception of Spark, C.W. or M.C.W. signals, covering the frequency range from 30 to 1800 Kc/s. It had three valves which clipped into fittings on the front of the amplifier: these were the first Naval valves to use Dull Emitter filaments.

  The first valve was an RF amplifier using a tuned anode circuit coupled to a second RF amplifier with resistance capacity coupling to an Upper Anode Band Detector (obtained by putting a 3 ohm resistor in series with its filament). Reaction from the Detector was fed to the anode circuit of the first valve by mutual inductive coupling. C.W. signals could be received by increasing the amount of reaction until oscillation occurred i.e. Autodyne reception.


  The K5 Heterodyne Unit was used for setting up the Receiver on any desired frequency. It was developed in 1922 for use as a separate heterodyne oscillator for reception of C.W. but it could also be used as a generator of M.C.W. by virtue of its Buzzer attachment, as a wavemeter and in emergency as a receiver itself. It covered the frequency range from 13.5 to 2500 Kc/s.

All the equipment mentioned above and below formed part of an exhibit in the Museum of the Royal Navy Electrical School, H.M.S. Collingwood. Sadly this museum close in 2022 and the exhibit and all its constituent parts became the responsibility of the National Museum of the Royal Navy.

Inductance Ae No1 Patt 2181	Radio Cabin	Switched Condenser	W/T Office 1920s	Inductance Ae No1 Patt 2181

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