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Army radio communication during the Great War Keith Thrower.

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Presentation on theme: "Army radio communication during the Great War Keith Thrower."— Presentation transcript:

1 Army radio communication during the Great War Keith Thrower

2 Circuits developed before 1914 Diode detector, patented by J A Fleming in October 1904 Soon superseded by the carborundum crystal detector, patented by Dunwoody in 1906 The Audion triode, patented by Lee de Forest in January 1907, and used initially as a detector. Its amplifying properties were not realised for several years Valve oscillator, patented by Meissner in April 1913 The heterodyne receiver, conceived by Fessenden in In its later form a valve oscillator was used to mix with an incoming ICW wave and beat it down to an audible tone Regenerative feedback from the output of the detector to its input to improve selectivity and increase amplification

3 Early radio valves (not to scale) Fleming diode & BT-H Audion Round C & T (‘soft’ triodes)

4 Marconi Short Distance Wireless Telephone Transmitter & Receiver This wireless set used a T.N. valve as an oscillator, directly coupled to he aerial circuit The C valve is connected as an RF amplifier with regenerative feedback to increase its gain and provide greater selectivity The output from the C valve goes to a carborundum crystal detector in series with the headphones

5 The Marconi 1.5 KW spark set At the start of the war the only radio equipment available to the army were a 500-watt set and, as shown here, a 1.5kW set mounted on two wagons each drawn be a team of 4 horses

6 Spark, CW & ICW Waveforms The top waveform shows a typical spark signal repeated every millisecond Below this is a continuous wave (CW) of 200 kHz generated by a valve oscillator The third waveform is that produced when the continuous wave is switched on and off by a Morse key. This is known as interrupted continuous wave (ICW) Spark transmitters were used throughout WW1 but ICW radios began to come into service from late 1916

7 No 1 Aircraft Spark transmitter The Royal Flying Corps (RFC) was first to use tactical radios 600 of these transmitters came into service during 1915 Transmitter box measured 8in x8in x5in. However, a heavy 6-volt accumulator was required to power it

8 Damped oscillations from spark generator It should be noted that the oscillations will be further apart than shown here Typically there will be between 100 and 1000 damped oscillations per second

9 W/T Trench Set 50 Watt D.C. (BF Set) Transmitter derived from the No 1 Aircraft Spark Simple receiver with carborundum crystal Came into service in 1915 Transmitter operated on 350, 450 & 550 metres Powered from 10V battery Total weight: 112lb Range 4000yd (2.3 miles) 1200 produced

10 W/T Trench Set 130 Watt Wilson Transmitter Division to Corps communication & Corp Directing Station Fixed spark gap with motor- driven high-speed interrupter Same wavelengths as BF Set: 350, 450 & 550 metres Range 9000yd (5.1 miles) with aerial supported on 30ft masts Powered by 26V or 28V accumulator

11 Crystal detectors Two types of crystal detectors were used in the receivers: 1. Carborundum, composed of silica and carbon, invented by Dunwoody in The Perikon, a combination of zincite & chalcopyrites, invented by Pickard in 1909 Carborundum was more robust but required a bias of 1½ to 3½ volts, adjusted by a potentiometer Perikon was more sensitive and did not require a bias battery, but was also more delicate in use and easily knocked out of adjustment Several army radios had both types fitted, with selection by a changeover switch A test buzzer was usually included in the radios

12 Tuner Short Wave Mk. III* Mk. III version introduced in Mk III* in 1918 Covered band 100–700m Used with Wilson 130-watt transmitter & for aircraft flying over trenches Carborundum & Perikon crystals in receiver Aerial 125ft wire laid along the ground as inverted L

13 Later valve developments (not to scale) Left) French TM of 1915 Manufactured in UK as R-valve in 1916 (Right) Type F transmitting valve. Derived from R-valve (Top) Marconi Q detector valve: 1916 (Bottom) Marconi V24 amplifying valve: 1918?

14 W/T Forward Spark 20 watt “B”. The Loop Set Used for forward communication There we both Rear & Front Stations & two versions of each They had a fixed wavelengths of 65m & 80m (5MHz & 3.75MHz) Transmitter had a fixed spark gap similar to the BF Trench Set Receiver had two valves, either the French TM or British R

15 W/T Set Trench CW Mk III* The transmitter & receiver were mounted in separate boxes Entered service in 1917 Transmission was by interrupted continuous waves (ICW), which required a heterodyne receiver Apart from the transmitter and receiver the complete station included a Selector Unit, a heterodyne wavemeter, an AC power unit and an associated rectifier unit

16 W/T Set Trench CW Mk III*: Transmitter Used for Forward area comms Transmitter rated at 30 watts Band covered: 450–1450m (207 kHz–667 kHz) Earlier Mk III version had single B or AT25 valve. This version had two valves Aerial 20 to 150ft depending on wavelength, supported by masts. Also 14ft earth mat Range 3.7 miles Approx manufactured

17 W/T Set Trench CW Mk III: Receiver This is the Mk. III receiver and has two R valves One is used as an oscillator to mix with the incoming ICW signal and beat it down to an audible frequency The other an AF amplifier connected to the headphones Approx manufactured There were also approx. 400 Selector Units manufactured

18 Telephone Wireless Aircraft Mk. II Special helmet produced with in-built microphone & headphones Wireless telephony from aircraft started in mid-1917 This set covered the band 350–450m (667 kHz–857 kHz) It had two B or AT25 valves Powered rom a 6-volt battery & a wind-driven 600-volt generator Aerial a trailing wire ft

19 Concluding remarks Army was slow to adopt wireless and relied too much on cable Genuine fear that wireless would be intercepted by enemy But this was equally true with communication by cable Cable was being constantly severed by shell fire and passage of tanks The first tactical radios to be used were those fitted in aircraft from 1915 to communicate with crystal receivers on the ground First trench sets came into service in the towards the end of 1915 After this the army slowly began to realize that wireless was a more reliable way to communicate than cable Only in last year of the war was wireless sets readily adopted by the army One wonders how much shorter the war may have been and lives saved if wireless had been adopted in large numbers from 1916 onwards when improved valves became available, making possible communication by continuous waves

20 Modulation of oscillator to produce ICW


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