ABSTRACTS OF RADIOCOMMUNICATION CONVENTION SURVEY PAPERS 493

COMPONENT DEVELOPMENT FOR WAR-TIME SERVICE APPLICATIONS

By I. M. Ross, M.A., B.Sc*(ABSTRACT of a RADIOCOMMUNTCATION CONVENTION paper which was published in 1947 in Part HI A, No. 11, of the Journal.)

The important part played by radiocommunication during thelate war owed much to the work done on improving the per-formance and reliability of the components used. This work isbriefly surveyed, attention being confined to the common classesof components, valves and other specialized classes beingomitted.

In general, the components available at the outbreak of warwere of standard commercial design; many were suitable onlyfor domestic applications. They had not been designed to meetthe severe conditions now known to be possible in Service use,and sooner or later during the war they gave trouble. Lack ofstaff and testing facilities at the Service Design Establishmentswas partly responsible for this state of affairs. Absence of co-ordinated effort between the several Establishments and withinindustry also contributed. Under the impetus of war these dis-abilities were largely overcome and a close degree of co-operationarose within the Services and industry and between the two,culminating, in so far as development work was concerned, inthe formation of the inter-Service Radio Components Researchand Development Committee, which through an extensive seriesof sub-committees is now responsible for sponsoring and guidingdevelopment work on radio components and materials.

During the war, industry was responsible for the bulk of thedetailed development work, the main contribution of the Estab-lishments being on the specification and testing side, although inthe case of specialized requirements considerable design work wasalso undertaken, sometimes including preproduction tooling andmanufacture where processes were involved in which seriousbottlenecks occurred in industry.

The need for improved reliability accounted for most of thedevelopment effort on components, followed in importance bywork on the development of miniature types. Extremes oftemperature and humidity were the main factors affecting relia-bility. Improvement in temperature performance was largely amatter of better grades of materials. Considerable advanceswere made, and ultimately components were available suitablefor a temperature range of — 40° to + 70° C, the main exceptionsbeing certain wax-protected components, which required a con-cession to — 30° C. In many cases safe upper temperatures of85° C were achieved, and in a few cases 100° C, the tendencyduring the war being towards higher and higher working tem-peratures in equipment.

Better resistance to humidity was mainly achieved by bettermethods of protection, and led in many cases to the developmentof hermetically sealed types, in preference to the use of pro-tective compounds as had been common previously and whichproved unsatisfactory under extreme conditions such as weremet with in the Far Eastern campaign.

Other adverse conditions of use having an influence on develop-ment trends were: operation in rarefied air; and exposure to saltspray, dust, sunlight, ozone, fungus attack, and mechanical stressarising from shock, vibration and acceleration.

After reliability the main factor affecting component designhas been the need to reduce size and weight. The extension ofcommunication facilities to smaller units, the need for powerfuland complex apparatus in the very restricted space available infighting vehicles, ships and aircraft, transport problems by airand over land, and the development of guided missiles—all wereinstances in which severe weight or size restrictions applied.

The main advance in the development of miniature equipment* Signals Research and Development Establishment, Ministry of Supply.

dates from the introduction of miniature valves of the B7G class.By joint Service action development work was also initiated ona complete range of miniature components. Not only had theyto be smaller and lighter than their earlier counterparts, but theyhad to be suitable for general Service use, and therefore had toattain a high degree of durability. Hermetic sealing was intro-duced for the first time in many of the designs as a means ofachieving high resistance to humidity, dust, etc. Examples in-clude: voltage dividers, relays, meters, crystal-holders, micro-phones and receivers, and plugs and sockets. Table 1 illustratesthe reduction in size achieved as compared with standard designs.

The Army Wireless Set No. 88 provides an example of thereduction in equipment size made possible by the introductionof such components. This is a 13-valve v.h.f. crystal-controlledtransmitter-receiver for infantry use. The overall size is5 | x 9 | x 3£ in, and the weight is only 5 lb.

Electrical influences on component design were: the trend tohigher radio frequencies, focusing attention on the need for areduction of stray inductance, capacitance and series resistance;and the need for high-stability circuits, which called for thedevelopment of highly stable inductors and capacitors in thesmall sizes demanded in Service equipment. Although advanceshave been made, development is not yet by any means complete.

From a mechanical point of view, the introduction of thetechnique of sealing the complete equipment as a means ofmaking it tropical and immersion-proof led to the developmentof a range of sealed panel-mounting components and controls.An air-leakage rate of 1 cm3/h under a pressure of 15 lb/in2 wasthe general standard aimed at and achieved in most cases.

In order to illustrate the advances made in design in theseparate classes of components the following may be quoted:fixed resistors measuring £ x £ in in diameter, rated at 0-1 watt;resistors with an overall stability of 1% ("cracked"-carbon type);hermetically sealed voltage dividers; high-precision wire-woundvoltage dividers (accuracy approaching 1 part in 10 000); paper-dielectric capacitors suitable for operation at 100° C; miniaturepaper capacitors (metallized type) down to one-fifth of earlysizes in the lower-voltage types; high-permittivity ceramic capa-citors, with dielectric permittivities of 1 200 and upwards;variable capacitors only two-fifths of the size of conventionaltypes; h.f. rotary switches less than one-half the size of earlierpatterns and using ceramic insulation; hermetically sealed andminiature relays, including normal-duty, heavy-duty, low-loss/low-capacitance and high-speed types; high-performance self-rectifying vibrators; hermetically sealed transformers and typessuitable for pulse working; moving-coil microphones and re-ceivers and sealed designs; matched-impedance coaxial plugs andsockets; sealed multi-pin power types, with up to 25-way facili-ties; li-in sealed moving-coil meters; high-stability quartzcrystals with deposited electrodes and sealed in glass envelopes.

Looking to the future, it is unlikely that there can be anygeneral relaxation on durability requirements for Service com-ponents, although there may be particular cases where furtherinvestigation will reveal that the existing standards are unreason-able. One instance where relaxation may be possible is in thecase of components for use in sealed sets. If field experience issatisfactory the moisture protection finally insisted on for thesemay be of only an elementary nature. Reduction in size andweight is likely to remain a strong trend in design; attention isalready being directed towards sub-miniature components andvalves. High-stability components are becoming of increasing

494 ABSTRACTS OF RADIOCOMMUNICATION CONVENTION SURVEY PAPERS

TABLE 1

Representative Miniature Components, illustrating Reduction in Size achieved

The dimensions quoted are approximate only and refer to the main body of the component. Dimensions are in inches or cubic inches." D " signifies "diameter." A similar type of "normal" has been chosen in each case, but the performances are not necessarily identical.

Component

Resistors, fixed carbon:^ W^w ;; ;. .; ;;

Resistors, variable:CarbonWirewound

Capacitors, fixed:Paper (0-1/iF)

Ceramic (470/*^uF)Electrolytic (8 u¥)

Capacitors, variable 2-gang, 300ju^FTrimmers, air-dielectric, 20 /</iF . .Switches, h.f. rotaryRelays:

Normal typeHigh-speed type

MetersMetal rectifiers, h.f.Fuses (cartridge)Quartz crystals (in holder)Plugs and sockets, 12-way:

Panel memberCable member (straight entry)

Miniature

Dimensions

0-44 X 0-16D0-25 X 0-12D

0-62 x 0-75 D(TVW)0-62 x 0-81 D

1-12 x 0-44D (350 V)0-62 x 0-31 D (150 V)

0-44 x 0-22D2-75 xO-75D(35OV)

1-75 x 1-7 X 20-97 X 0-62 x 0-64

1-25 x 1-25

2 x 1 - 7 x 12-2 x 1-1 x 0-75

1-2 x 1-75D0-6 x 0-22D0-62 x 0-19D

1-15 X 0-8 X 0-45

1 x 1-34D1-9 x 1-38D

Volume

0 00810 0028

0-270-32

0170-04700171-25-90-391-6*

3-41-82-90 0230 0220-41

1-42-8

Equivalent normal

Dimensions

0-625 X0-25D

0-5 x l - l D ( i W )0-75 x 0-94D

1-5 X 0-5 D (350 V)—

1-37 X 0-41 D2-75 X 1-57D(375V)

2-8 x 1-8 X 2-91-44 x 0-94 x 1

1-75 x 1-875

3-4 X 2-1 x 1-13 x 1 - 4 x 11-3 X 2-2D

1-45 X O-38D1-25 X 0-25D

1-6 x 0-7 X 1-75

0-97 x 2-03D216 x 1-8D

Volume

0031

0-480-52

0-29

0 1 84 1

151-43-3*

7-85-24-90 1 600622 0

3 15-6

Ratio ofvolumes

3-8

1-81-6

1-7

113-32-53-52 1

2-32-91-77-12-84-8

2-22

Remarks

Miniature "Hi-K"

*Area of wafer, in2

\ Miniature types,/ sealed

Miniature type, sealedMiniature type, sealed

\ Waterproof screened/ type

importance, and interest is being directed towards sub-unitchassis in ceramic with fired-on wiring and integral coils andcapacitors.

Some of the new materials now entering the applied stage mayrevolutionize our components, notably the silicones as low-lossstructural materials, and the high-permittivity ceramics and high-permeability ferrites for capacitors and coils respectively.

One of the big problems facing those responsible for Servicecomponents is how to align Service and domestic types so thatlittle difficulty will be met in rapidly expanding production intime of war. A partial answer can be found by ensuring thatService designs do not merely meet their respective requirements,but that they do so with a minimum departure in design andconstruction from domestic types.

BIBLIOGRAPHY OF RADIOCOMMUNICATION CONVENTION PAPERS(Abstracts of the Addresses delivered and of the Survey Papers read at the RADIOCOMMUNICATION CONVENTION, March and April, 1947, will be

found in this issue, commencing on page 463. A bibliography of the remaining papers is given below.)

ABBREVIATIONS

The numbers in brackets refer to the issues of Part IIIA inwhich the papers are being published. The abbreviations referto the following classification, which is based on the sessions ofthe Convention:—

C—C.W. Navigational Aids.D—Direction-Finding.L—Long-Distance Point-to-

Point Communication.M—Military and Aeronautical

Communication.N—Naval Communication.

P—Propagation.PC—Pulse Communication.

R—Radio Components.S-I—Short-Distance Communi-

cation: U.H.F.S-II—Short-Distance Communi-

cation: V.H.F.BAKER, W. N.: "Standing-Wave Indicator for 3-22 Mc/s." (No. 12,

L.)The use of a midget diode for rectification at the transmission line, followed by ad.c. amplifier and milliameter, avoids the defects of the more usual thermocoupleinstruments and expensive microammeterS by providing a robust instrument ofwide range.

BALLANTTNE, R. J., and JAMES, E. G.: "Oscillator Circuits for Wide-Range Tuning." (No. 14, S-I.)Design and operation of circuits to cover wide tuning ranges at ultra-highfrequencies. ' '' ' • *:••"•• J J > v ' i t e

BARFIELD, R. H.: "Statistical Plotting Methods for Radio Direction-Finding." (No. 15, D.)The general problem of "fix" interpretation and its solution.

BELL, D. A.: "Choice of Frequency for V.H.F. Radio Links." (No. 14,S-II.)Consideration of aerial characteristics and diffraction attenuation for distancesbeyond the horizon.

BBRCHALL, M.: "C.W. Radio Aids to Approach and Landing."(No. 16, C.)Problems involved in the design of landing approach systems for the guidanceof aircraft in azimuth and elevation, with their psychological and aerodynamicconsiderations.

BLAKE, K. W.: "External Cross-Modulation in the 100-Mc/s Band."(No. 14, S-II.)Cross-modulation between v.h.f. equipments on ships, due to parts of the ship'sstructure acting as non-linear conductors.

BOOTH, C. F., and JOHNS, J. P.: "The Development of Quartz-CrystalProduction.'' (No. 16, R.)The development of mass production of quarti^rystal vibrators during the war,and the solution,of problems connected therewith.