Exp. 526 Transmitter Telephone, Ground Type. This is a two-valve transmitter using T2B valves for power and control. There is a tuned reaction and a four-value aerial condenser. H.T. supply is at 1000v. to 2500 v DC. The L.T. supply is 12 volts for filament lighting.

The transmitting set is shown in photograph No. 1 and the complete set in photograph No. 2.

Exp. 528 Comparison of American Signal Corps Microphones with the R.A.F. Standard Air Type.

A series of comparative tests in the air were carried out between the R.A.F. Standard Air Type Microphone and four types of American Microphones all designed for transmitting speech from the air.

Exp. 528 Comparison of American Signal Corps Head Receivers with Various Other Types. Bench and air tests were carried out and the Signal Corps head-receiver was recommended as a type which could be adopted as universal for all ground and air work in the R.A.F.

Exp. 518 Two-Way Telephony. Inter-communication comparisons were made with a one-wavelength or two-wavelength system. See diagrams in Fig. 1088, 1089 and 1090.

Exp. 600 C.W. Telegraphy and Telephony from Rigid Airship No. 31 using T.57. Trials were carried out using airship No. 31 near Bedford to ground station mast at Aperfield Court.

Exp. 627 Alterations to T.H. Amplifier for Waves up to 14,000 metres. To be able to use the T.H. Amplifier for wavelengths between 8,000 and 14,000 metres, alterations are required. Audibility curves are shown in diagrams Fig No. 1086 and 1087.

Exp. 673 7-Valve H.F. Tuner for 6th. Brigade H.D. This Tuner (as shown in photograph on page 19.) was designed for listening-in Station at the 6th. Brigade Head Quarters, primary for checking Wireless Telephony Transmission on 400 – 450 meters.

Exp. 654 Tuner Air R.A.F. Type 10. This tuner has now passed through the experimental stage and one instrument has been sent to America as a manufacturing example.

Exp. 671 Test of Constant Speed Windmill. The standard 7¾” diameter windmill was compared with various forms of experimental windmills. See diagram Fig. 1091. and photographs on page 24 showing front and side views of the new windmill compared with the standard windmill of 7¾” diameter.

Exp. 636 Size of Windmill for B.T.H., H.T. Generator fitted to Avro Two-Seater Biplane. The diameter of the Standard Windmill for B.T.H. Generator for Avro machines is 18 inches. The Generator was fitted on the back V-struts of the undercarriage in the centre, laterally.

Exp. 668 Tests of Murphy D.C. H.T. Aircraft Generator. The generator is double wound and is designed to give a maximum output of 2 amperes at 7 volts, and 0.2 amperes at 700 volts, with a nominal speed of 5,200 R.P.M. Page 26, photograph No1 shows generator brush gear and commutators. Photograph No. 2, with outside casing and armature removed.

Exp. 621 combined with Exp. 630. Selective Attachment to Tf Receiver for all Ranges. This is still awaiting completion in the W.E.E. Workshops. A report will be made later.

Exp. 669 Report on Tests of “Marsha” Lamp, (Ultra Violet Light) at W.E.E. The object of this test was to ascertain if signalling could be carried out from the ground to an aircraft at night without exhibiting and light visible to the naked eye.

Exp. 604 Magneto Noise Elimination. A continuous series of experiments has been carried out to determine the exact cause of magneto noise.

Exp. 667 and 670. Investigation of degree of control obtained in Telephone Transmitters when using Chokes of various electrical dimensions.

The best telephone control would probably be obtained by using a choke of very large inductance, but for reasons of weight, space and cost, it is to be investigated how size can be reduced without effecting degree of control. See diagram No. 1092, 1093 and 1094.

Exp. 507 and 664. Telephone Transmitter for Fixed Aerials. An experimental set has been made up and tested on a Fixed Aerial. A good aerial output was obtained, but no reception was carried out due to the wave-length of the experimental transmitter being too low for the receiver. Further experiments are in progress and will be reported on later.