The Wireless-Set-No19 Group


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Wireless Set No. 13.— this is a V.H.F. (metre wave) combined transmitter and receiver (transceiver) operating on a frequency band in the region of 60 Mc/s (5 m.); it has a super-regenerative receiver and has therefore poor selectivity.
Thirty sets, based on an S.E.E. model, were manufactured by Messrs. E. K. Cole, Ltd., and issued for trials in 1936. Twenty-four were sent to Infantry Units and 6 to the Tank Brigade. The main purpose of the trials was to ascertain whether the propagation characteristics of wavelengths of the order of 5 metres were such as to make them suitable for military use at short ranges (e.g. ranges up to half a mile). The reports on the trials indicate that such wavelengths are unsuitable for short-range military work. as communication was found to be very greatly affected by the general nature of the intervening counry.
A few No. 13 sets were taken to Patestine by the 1st Division

Wireless Set No. 6 - A sender has been completed for Hong Kong and, with a special receiver made by the G.P.O., was under trials at S.E.E. at the end of the year. These were satisfactory and the sender will be despatched in early 1934. The receiver is a highly complicated, very selective apparatus, and will be kept at Aldershot until more experience has been gained of its performance in the hands of troops.
The set at Adershot has continued to give good service, though its frequency had not been quite sufficient to comply with the tolerances permitted under the Madrid Telecommunications Convention in 1932, which came into force on 1st January 1934. The fact is mentioned as of interest, since the set is crystal-controlled, and to indicate that, although this is the case, operating controls can and do affect the emitted frequency. A type of pilot meter to inform the operator of any departure from the proper frequency is under design.
The problem of the best frequencies to use at various reanges, in various conditions of light and darkness over the path, and in various phases of the sunspot period, is still being investigated, but it is hoped that sufficient data will have been accumulated by the Spring of 1934 to enable certain frequencies to be registered at the Bureau of the Union at Berne for regular traffic working to Egypt. Palestine, India and Hong Kong.
With a view to standardizing the aerial equipment for the No. 6 Set a pair of lattice steel masts were erected by a R. Signals party from "A" Corps Signals, at S.E.E. These are of Messrs. Milliken's design, 125ft high, self-supporting, and are suitable for holding up certain forms of aerial array, such as the Kooman's type. If the sub-soil is suitable, they can be erected on their own girder foundations, without concrete but, if the water table is near the surface, concrete foundations are necessary.
Tests of the Kooman's half-wave horizontal aerial array have been made at Aldershot, and a small improvement in signal strength has been noted at the receiving ends. It is proposed to test the Bruce horizontal diamond type of array if the necessary ground space can be made available. This type of array has the military advantage that it is tolerant of a wide range of frequencies, whereas types using half-wave components are inefficient except on the frequency for which they are designed. The gain is about the same on the average for each type.

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