Exp. 504 Spark Rectified Set. C.W. (Stirling Coil) A more powerful receiver would be required to increase range, see Exp. 520.

Exp. 507 Telephony between aeroplanes on fixed aerial. A trial was made to find the effect of a short trailing aerial in connection with a fixed “T” aerial. Increased range achieved from a trailing aerial.

Exp. 509 Long Distance C.W. Receiver (Modified 131 H.) A receiver with 3 L.F. Magnifications. No progress. Used from time to time as necessary.

Exp. 510 Microphone Fitting to Oxygen Mask. The mask was fitted with a thin leather cover over the back of the inset to determine whether it would lessen the outside noise.

Exp. 514 G.W. Transmitter from Ground to ‘Plane, Range 25 miles, Tonic Train. Design completed. Set sent overseas. Working quite satisfactory.

Exp. 517 & 518. Testing Set. Aircraft, Mark II Transmitting and Receiving. Designs completed, samples made.

Exp. 518 Testing Set, W/Tn, Aircraft, Mark II. Receiving and Dummy Receiving Aerial. The Dummy Aerial makes adjustment of the receiver possible on the ground before flight.

Exp. 519. Transmitter, W/T Aircraft C.W. M.K. II. Designs completed, samples made: manufacture in hand.

Exp. 520 Simple C.W. Ground Receiver. (See Exp. 504) This receiver, a single valve oscillating on its own filament battery, was found too feeble for E.F. work in conjunction with 504.

Exp. 521 Telephony Intercommunication onto Planes. Experimental trials of an aircraft fitted with Lieut. Cohen’s throat microphone.

Exp. 528 C.W. Valve Relay for Aeroplanes. An account of progress has been published in S.E.E. Report for May.

Exp. 524 & 507. Reception on Pagoda Tuner and Modified Fixed Aerial. The purpose on comparing reception on the Pagoda Tuner and modified fixed aerial. Marconi valves were a considerable improvement on the French valves. Transmission between aircraft D.H. 4, 7689, and B.F. 4611.

Exp. 526 Ground to Air Telephony (Long Range) Nothing further to report.

Exp. 526A Ground to Air Telephony (Medium Range) The 5 stations following are now working, viz: Northweald, Stowmaries and Bekesbourne. A range of 20 miles has been obtained from Northweald using a 200ft aerial in a Bristol Fighter.

Exp. 527 Microphone Head Receiver. Progress delayed through lack of material and removal of laboratory from Woolwich to Biggin Hill.

Exp. 528 Western Electric Telephone Set-Two Way Working Between Machines. This set (a change-over switch) is a combined arrangement for transmission and reception of telephony between Sopwiths A5252 and A8270 and also telephony between Pilot and Observer.

Exp. 528 Report on Crocker Wheeler Generator as Supplied with Western Electric W/Telephone Sets. This generator gives excellent voltage regulation and to give constant voltages over a range of speeds from 4000 to 8000 R.P.M. The set was fitted to a Sopwith 2-seater in the slip-stream of the main propeller.

Exp. 530 Magneto Noise in W/T Aeroplane Receiver. Correction for monthly report for April.

Exp. 531 Instructional Sets. No progress made. Parts are awaited from Greenwich.

Exp. 530 Magneto Noise Tests on D.H.9. Machines. Tests were made to ascertain if the induction from the ignition system would interfere with the reception of wireless telephony. Two machines were used, No. 7652, which was fitted with ordinary ignition leads and No. 7651, which was fitted tinned copper braided ignition leads.

Expts. 530, 529, and 507. Magneto Noise Tests on D.H.4 Machine with Marconi H.F. Tuner and Earth Wiring in Machines. Machines have been earth wired throughout with copper strips bonding engine, tanks and all metal work to reduce Magento noise.

Exp. 601 C.W. Transmitter T.56c for Rigid Airships. Little progress made in Experiments 601 – 616, and 638 as the greater part of the month was spent packing and removal of apparatus to Cranwell.

Exp. 602 C.W. Syntonizer (Long Wave) No data.

Exp. 604 Magneto Noise Elimination. No data

Exp. 605 Listening-Through Key for T.57. No data

Exp. 606 H.F. Amplification on Short Waves. No data

Exp. 607 Pure C.W. Transmission with A.C. Supply. No data

Exp. 608 Direction Finding No data

Exp. 609 Wave Forms and Energy Losses in Valve Circuits. No data

Exp. 614 Magneto Transmission No data

Exp. 616 Negative Characteristics Valves. No data

Exp. 620 Call Up Variometer for T.56b. and T56c. No data

Exp. 628 Amplification of 5-Valve Model 606 for Different Wavelengths. Correction of April Report.

Exp. 638 Frequency Changes. No data

Exp. 618 New Wireless Telephony: Control of Aerial Currents. Experiment proceeding but not yet completed.

Exp. 619 Davis Accumulator Nothing to Report.

Exp. 633 Dual Reception of Spark and C.W. Addition of a third circuit for Spark and C.W. Transmission. The circuit is shown diagrammatically in Fig. 1003.The spark circuit used was an ordinary Shortwave Tuner Mark III. The C.W. was a built-up circuit on the bench, but any standard instrument could be used.

Exp. (507, 524, 529, 606, 634) Wireless Telephone on 400 Metre Wavelength between Aeroplanes with Fixed Aerials using Short Wave High Frequency Amplifiers: Summary of Comparative Tests of Amplifiers.

5-Valve (Pagoda Amplifier (Exp. 524) Of the four this seems to be the simplest for use in 400 metre telephony in the air

5-Valve, (Cranwell Experimental Model) (Exp. 606). This Amplifier did not give very satisfactory results in the air, the maximum range obtained being only 1½ miles.

6-Valve (Marconi Experimental Model) (Exp. 529) A range practically equal to that of the “Pagoda” was obtained. The instrument is reliable and valves easily changed.

7-Valve (Whiddington Experimental Model) (Exp. 634) This instrument gives greater range and intensity than any of the others, but it is rather susceptible to magneto disturbances.

Exp. 634 7-Valve Receiving Amplifier. The range obtained is apparently very good and gives indications of being a considerable improvement on the 5-valve amplifier. Transmission was from a DH 4, aircraft No. 7689 and a BF. No. 4811.

Exp.635 Telephony Between Single Seater Scouts. Nothing further to report.

Exp. 636 Propeller Adjustments on Various Craft. B.T.H. Generator now being fitted to “Handley Page” for trial.

Exp. 637 Slip Stream Air Speed Measurements. An exhaustive series of tests using Pitot tubes has been made in which the speed of the slip stream was determined in a variety of positions on all aeroplanes available. Tests Nos. 12 – 22.

Exp. 639 Two Way Wireless Telephony from Kite Balloon to Ground. Perfect intercommunication was maintained between the balloon and the Ground Station at Croydon a direct distance of 7½ miles.

Exp. 640 Shed Tests of T.S. 2A. No progress owing to dismantling of Cranwell W/T/ Section.

Exp. 641 Galvanised Iron Earth Mats. Comparison of the aerial current of iron wire earth nets and a standard copper earth mat

Exp. 642 No further progress to report.

Exp. 643 Receiver, C.W. S.W. 150-300 metres wavelength. Correction of April report. No further progress to report but experiments proceeding.

Page 33 Diagrams Fig. 1003 and Fig. 1005