AND RADIO REVIEW (141h Year of Publication) No. 379 WEDNESDAY, DECEMBER IST, 1926. VOL. XIX. No. 22. Assistant Editor: Editor: Assistant Editor: F. H. HAYNES. HUGH S. POCOCK. W. JAMES. Editorial Offices : 139 -4o, FLEET STREET, LONDON, E.C.4 - - Telephone: City 4011 (3 lines). Advertising and Publishing Offices : DORSET HOUSE, TUDOR STREET, LONDON, E.C.4. Telephone : City 2847 (13 lines). Telegrams: "Ethaworld, Fleet, London." COVENTRY : Hertford Street. BIRMINCHAnt : Guildhall Buildings, Navigation Street. MANCHESTER: 199, Deansgate Telegrams: " Cyeat Coventry' Telegrams: " Autoprees, Birmingham.' Telegram, : "Ilifle. Manchester." Telephone : 9210 Coventry. Telephone . 2970 and 9971 M.dland. Telephone: 8970 and 8971 City. Subscription Rates : Home, t7s. 4d.; Canada, 17s. 4d.; other countries abroad, 19s. 6d. per annum. As many of the circuits and apparatus described in these pages are covered by patents, readers are advised, before making use of them, to satisfy themselves that they would not be infringing patents. THE CHRISTMAS SEASON. their own. Christmas provides an excellent opportunit, for extending interest in wireless, and there is every pros VERY year, as the Christmas season pect that under the new control in 1927 the broadcast approaches, our thoughts naturally turn to service will be improved, due to the fact that a very a consideration of what can be done in the considerably greater sum will be available for expenditure way of providing for Christmas enter- on the programmes, whilst, in addition, the higher tainment. In many powered stations and alternative cases wireless itself programme policy already ap- has simplified this CONTENTS. proved will do much to add to the task by music a bringing of PAGE attractiveness and utility of the seasonable character to every EDITORIAL VIEWS ... ... 723 broadcasting service throughout home, but to a great extent the TILE NUCLEUS RECEIVER ... 724 the country. mere novelty of wireless has begun By H. F. Smith. 0000 to wear off, and we now regard it as an essential rather than an addi- READERS' NOVELTIES ... ... 730 WIRELESS AND THE tional - and novel form of entertain- CHRISTMAS NOVELTIES ... 731 BLIND. ment. As a consequence, we must By A. P. Castellain. APT. Ian Fraser, M.P., the look round in other directions for CURRENT TOPICS ... 737 blind chairman of St. Dun- novelty. stan's,is to be congratulated on the PRACTICAL HINTS AND TIPS ... 739 This must be our excuse for success of his Bill exempting blind introducing in the present issue of WIRELESS CIRCUITS IN THEORY AND persons from requiring a broad- The )Wireless World some ideas PRACTICE ... ... ... 741 j cast receiving licence, which has for Christmas entertainment which By S. O. Pearson. now passed through all its stages are not all of them strictly wire- BROADCAST BREVITIES ... 745 ; in the Commons and is expected to less in character. No attempt has, pass through the Upper House of course, been made to deal with PIONEERS OF WIRELESS (37) ... ... 747 before Christmas. Capt. Fraser, more than a representative few of By Ellison Hawks. ill introducing the Bill, expressed the many ideas which could be NEW APPARATUS 749 the hope that it might become law adopted, but, no doubt, the reader LETTERS TO THE EDITOR ... 750 before Christmas and thereby con- with wireless experience will be stitute a Christmas gift to the READERS' PROBLEMS ... ... ... 752 able to modify and extend these blind. Wireless is appreciated by schemes in many 'directions to suit the blind to an extent probably far his own requirements. greater than it is possible in the Wireless. has another advantage at this time of the case of those who have the advantage of their sight. year, since it solves for us so easily the question of what Capt. Eraser's name is so intimately associated with to give as a Christmas present. To those who already broadcasting to -day that all those interested in wireless own a wireless set there are always many accessories in must naturally feel that they have a special link with the a wide range of prices which provide most attractive pre- work of St. Dunstan's. The eleventh annual report of sents, whilst one could scarcely imagine a more acceptable St. Dunstan's has just been issued, and is a revelation to present than a complete valve receiver or even a simple those unacquainted with the splendid work which is being crystal set for those who have not yet installed a set of done by this growing organisation. $ 5 www.americanradiohistory.com-ve 7,4- 1.1 -.a-:_. It! t;we'"40,-K+*!!4.*,-ty?l`-dEkSMf.'7Rbti.tL?+R^:ak tert4rje.eiff OwlioN540.41-4**1' _ - NYfipghoo DECEMBER ist, 1926. WopIlcl A " Local Station " Loud =speaker Set Arranged for the Addition of H.F. and L.F. Amplifiers. the earliest days of broadcasting the so- called enormously since those " bad old days," and it is now " unit " receiver enjoyed eery considerable `popu- possible to construct a single -valve amplifier which, on the larity; indeed, a large proportion of the ready -made broadcast wavelengths, will magnify the voltage due to sets offered for sale were constructed on this plan. It is an incoming signal about forty times; this by pure valve rather interesting to speculate on the probable cause of its amplification, without taking into account the very con- decline in favour ; although the arrangement is undeni- siderable increase possible by the judicious use of reaction ably convenient, it is seldom advocated at the present On the T..F. side an equally happy state of affairs exists, time. The writer has a shrewd suspicion that it was due to the fact that the addition of amplifying valves, whether H.F. or L.F., did little more than make evident the poverty of the land in a most convincing manner, and thus caused the user to become dissatisfied with his re- ceiver. The L.F. stages, while certainly increasing volume, amplified distortion to a still greater extent, while the H.F. valves, as far as the shorter wavelengths were concerned, did little more than render the whole set unstable and extraordinarily difficult to operate. Luckily, our knowledge of H.F. work has increased Fig. 2.- Showing the effect of grid condenser reactance. as valves and couplings are available which will give a high degree of amplification without appreciable dis- tortion. Advantages of the Unit System. It has been urged by opponents of the unit system that the apparatus occupies a very large, amount of table space, and it must be admitted that there is some justifica- tion for this complaint, although the instrument to be described in this article, consisting of detector and L.F. amplifier, together with an additional H.F. and an L.F. unit, only measures about 32ins, long, which can Fig. 1. -The simplified circuit diagram. hardt`y" "be considered as excessive. B 6 www.americanradiohistory.com DECEMBER Ist, 1926. WATasoo 72S WOpIlGl The. Nucleus Receiver. - Readers of this journal will have noticed that the de- signers of the majority of receivers making use of highly +H.T. efficient H.F. amplification have only made provision for covering the broadcast wavelengths, or have compromised, for long -wave work, by cutting out the high- frequency amplifying stage entirely. It is difficult to express a defi- V2 nite opinion as to whether means will be found for over- AERIAL coming these difficulties without any appreciable sacrifice efficiency, is very diffi- í -p of but it certain that considerable it F 3 C6 ñ culty will be experienced in designing a reasonably simple á Cl 4 'C` set, as a single instrument, to cover all broadcasting wave- Pz g? lengths from about 3o metres upwards, and at the same IIH L.T. + time retaining H.F. amplification at all frequencies where LT /- its use is found to he practicable. It is in this direction KT.- H.T LT that the unit set scores heavily. POTE Having briefly discussed some of the pros and cons of the system, we will consider the circuit of the nucleus r r +O.B.- +L.T.- + to which both H.F. and L.F. amplification may be added. H.T. - It is given in simplified form in Fig. i, and will be recog- r nised as embodying the essentials of the receiver recently Fig. 3.-The schematic circuit diagram showing connections to described by the present writer under the title of " The sockets for joining to other units. C1= 0.0003 mfd. ; C2 =0.1 mfd. ; C3 =0.0003 mid.; C4 =0.001 mfd. ; C5=2 mfds. ; R1 =15 Economy Two. "' With slight modifications as to capa- ohms; R3 =6 ohms; R3 =1 megohm; R4 =5 megohms. cities and resistance etc., to suit its special func- values, L.F. stage of the " Everyman's Four " receiver,2 which tions, it is in principle to the detector and first similar has been extremely popular with readers of this journal. ' The Wireless World, October 27th, 1926. The first valve functions as a " bottom bend " detector, The Wireless World, October 13th, 1926. and to enable a critical adjustment of grid potential to Rear view of the receiver. Note the mounti of resistance and condenser clips on porcelain bases. By www.americanradiohistory.com 726 WfipaSOM DECEMBER 1st, 1926. WWOOpild The Nucleus Receiver. - be made, a potentiometer is fitted in addition to a bias battery. This refinement only necessary when dealing with very weak signals. The detector is coupled to the L.F. amplifying valve through a high anode resist- ance and a condenser of con - siderably lower capacity than usual. Lest there should be any uneasiness as to whether the use of this small con- denser will result in an undue reduction of voltages corresponding to the lower audible frequencies, it will be as well to consider for a moment what is actually hap- pening.