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| Mark III Short Wave Tuner article | Mark III Short Wave Tuner
In World War I, the British used Mark III Short Wave Tuners in the trenches. Jonathan Hill writes that this early crystal set "was used by the R.F.C. ground stations for the reception of Morse Code signals transmitted from aeroplanes flying above the battlefields of the Western Front. The pilot’s job was to direct the gunfire of artillery batteries on the ground via an R.F.C. wireless operator attached to each battery. With a clear view of the battle scene below, the pilots would transmit in Morse the coded position of the enemy…and the message would be relayed on to the gunners who would then take the appropriate action" (Hill, Radio! Radio!, p. 26). This may seem primitive by today’s standards, but it was a technological revolution in its day. It allowed artillery soldiers to be much more accurate than they could have been without knowing the enemy’s position and the results of their shelling.
Marconi's Wireless Telegraph Company first developed the Mark III Tuner in 1915. From 1916 it was manufactured by a number of companies, including Robert W. Paul, the W/T Factory, A.T.M. Company, and Johnson and Phillips.
Robert W. Paul of London manufactured the Mark III that is in my collection. High quality parts and workmanship was used in the manufacture of the set
Most Mark III tuners were covered with black painted canvas; however, the mahogany finish of the Robert W. Paul tuner is the original finish. I restored the cabinet by repeated washings of a very thick coat of dust and dirt that seems to have offered protection to the original finish. The number “1” painted on the front of the case appears to be original and is presumably the number of the set in a R.F.C. squadron group. This set, to my knowledge, is one of only two surviving Mark III Short Wave Tuners that originally had attached folding aluminum legs, presumably to keep the radio off the ground and out of the mud.
The Mark III Short Wave Tuner is a crystal set utilizing both carborundum and Perikon detectors. It covered the 100-700 meter wave range. There were several makers and several variations; the Mark III Tuner shown in the picture is an early one, dating from 1916.
A box built into the lid of the Mark III Short Wave Tuner holds additional crystals. A valve can be hooked in place of the crystal detector; a switch on the right side of the set can be moved to select the carborundum detector, the Perikon detector, or an outboard valve.
The Mark III is tuned with the use of a buzzer. First the detector switch is set to the Perikon detector. The inductor and variable condenser are set to the estimated wavelength for receiving a particular station. Then the switch for the buzzer is pressed; this produces oscillations that act as if a station is transmitting at the estimated frequency. Finally, the various tuning knobs are adjusted until the loudest sound is heard in the earphones; the detectors also are adjusted for the loudest sound, and the buzzer is turned off.
The Mark III Short Wave Tuner is ready to receive.
Hill, Jonathan, Radio! Radio! (London: Sunrise Press, 1986).
Copyright 2001 by John V. Terrey. Reprinted with permission of Antique Radio Classified where it was first published in July 2001. For a free sample issue, write A.R.C., Box 2, Carlisle, MA 01741
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