BUILD A MOVING -COIL LOUD SPEAKER MODERN.MONTHLY IRIETSS Edited by NORMAN EDWARDS Vol. IX. No. 18. JUNE, 1928. TUL- ZoMZUR sCIcO Cj oMaE www.americanradiohistory.com `1vI C:k\ \4lkti.1:.-, June, 1928 WONDIZF ilL Nov VALVI l With the Mullai'd PM FIlament.. .«wil. Mullard always leads ! Max. Fil. Volts - 4.0 The new Mullard P.M.4D Fil. Amps. _... 0.1 has no equivalent ... it is Max. Anode volts 125 the ideal valve for perfect *Imped. (ohms). 6,000 detection and transformer *Ampli. factor .... 12.5 coupling. *Mut. Conduct. Low impedance. 2.1 mA!volt. Large amplification. *At Anode Volts 100, Grid Volts Zero. Consuming only 0.1 amp. at 4 volts and possessing all the advantages of the wonderful Mullard P.M. Filament. The valve for every four.volt valve user. Obtainable from all radio dealers. PRICE 12/6 EACH In Irish Free State, 13;' Q ùllard THE MASTER VALVE www.americanradiohistory.com June, 1928 MODERN WIRELESS \\\\\ Vol. IX. No. 18. MODERN WIRELESS JUNE, 1928. Pane Pase Editorial 579 The " Harris " Crystal Set .. 621 Microphones in Music Halls .. .. 580 Radio with tirenfell in Labrador 625 Why I Believe in Radio .. 581 The " Quick-Change " Four .. .. 629 The Sydney Two" de Luxe ., 583 Radio and the Gramophone .. .. 635 Loud -Speaker Positions .. 588 Radio Abroad .. .. 640 Listeners Likes and Dislikes .. .. 58 4 My Broadcasting Diary . 641 What are Cathode Rays? .. .. 591 Operating the " Easy -Tune Four .. 643 A 900,000 -Volt Tube .. .. 593 How Your Broadcast is Provided .. 645 Television by Cathode Rays .. .. 595 Dust-The Enemy .. .. .. .. 648 A Three -Valve Portable .. 599 Valves for Portables 649 Those Classical Broadcasts . 605 American Views on Home Television 650 A Moving -Coil Loud Speaker 807 In Our Test .Room .. .. .. 651 Questions Answered .. ., 610 What Readers Think ,. 654 That Indispensable Inductance 611 Television Notes of the Month ., 658 A Choke Unit Aerial 613 In Passing .. .. .. .. .. , 659 On the Short Waves .. 616 Vampire Valves .. .. .. ., 662 Standard Coils . .. .. .. 617 Radio Notes and News .. .. .. 666 As some of the arrangements and specialities described in this journal may be the subject of Letters Patent the amateur and trader would be well advised to obtain permission of the patentees to use the patents before doing so. Edited by NORMAN EDWARDS. Technical Editor: G. V. DOWDING, Grad.I.E.E. Scientific Adviser: J. H. T. ROBERTS, D.Sc., F.Inst.P. Construct the MAGNUM Construct the STANDARD M.W. LOADING COIL "SYDNEY" TWO " QUICK -CHANGE" FOUR as described in this issue. 1 Mahogany As described in this issue. Cabinet, with 12, Baseboard 1. 5 O as used in the 1 Ebonite Panel, 14" x 7", ready drilled 6 0 £ s. d. 1 Copper Screen for above, as described 2 6 1 Ormond 0005 Condenser, 1 Mahogany Cabinet with 12" Baseboard ... 2 2 0 ' Ouick-Change ' with S.M. Dial 13 6 1 Cyldon Condenser, 00025 ... ... 9 6 1 Ebonite Panel, 211 x 7", ready drilled ... 9 0 2 Vibrating Valve Holders . 4 0 2 Magnum Panel Brackets . .. ... ... 2 6 Four described 1 R.I.-Vartey Straight Line Transformer .. 1 5 0 4 Magnum Antiphonlo Valve Holders . ... 8 0 1 Magnum Neutralising Condenser ... 5 O 2 Magnum Standard M.W. Loading Coils (as in this issue. 2 Magnum used in the original set described) ... ... 15 0 Panel Brackets (small size) 1 6 1 Magnum Terminal - 1 Magnum Condenser ... ... 5 0 Panel with 7 Indi Neutralising eating Terminals ... ... 2 Magnum H.F Chokes .. ... ... 15 0 Price ... 3 6 1 Magnum Terminal Pal with 3 Indi- 1 Magnum Terminal Strip with 8 Indicating cating ... Terminals ... ... ... ... ... ... ... 4 O Terminals ... ... ... 1 6 1 Interchangeable Choke with Base 5 0 1 Magnum Terminal Strip with 2 Indicating 2 ... ... ... ... 1 O 7/6 Lissen Base -Mounting Rheostats .. ... 3 0 Terminals ... ... 1 Lissen Grid 2 Condensers, 0005 mfd.... 1 1 0 Leak and Corn binator ... 1 6 Igranic Lokvane 1 Lissen Base Mounting Potentiometer 1 1 Cyldon Reaction Condenser, 0001 ... ... 7 6 ... 6 1 Lissen 0003 Fixed Condenser .. ... 1 0 2 Liasen Fixed Condensers, 001 ... ... -. 2 0 2 Lissen 0005 Fixed Condensers 1 -0003 ... ... ... 1 O ... 2 0 Lissen Fixed Condenser, 1 Lissen 001 Fixed Condenser ... ... 1 1 Lissen Grid Leak, 25 meg. ... ... ... 1 0 ... 0 1 1 Igranic On -Off Switch 2 6 1 Lissen Grid Leak, 2 meg .... ... ... ... O 1 Special Coil, ready wound with' Base and ... ... ... 1 0 Specialists in Components and constructional 2 Grid Leak Holders ... Clips ... ... ... ... ... ... ... ... 7 O ... ... 7 6 1 Dubilier R.O.C. Unit Connecting Wire and ... 2 Dubilier Mansbridge Condensers, 2 mfd. 7 0 Kits for all sets described in " Modern Wire- Flex ... ... 1 0 1 Márconiphone L.F. Transformer (low ratio) 1 5 0 less " and " Wireless Constructor." 3 O 1 British General L.F. Output Choke, 20 £6 henries ... ... ... ... ... 130 O Comprehensive range of lists including several 1 Copper Screen, as described ... ... ... 3 6 2 Special Coils with Bases ... ... ... ... 17 6 new Magnum Products will be sent on receipt MAGNUM Wire and Flex ... ... ... ... 1 6 H.F. CHOKES Connecting of stamp. These compact and light £11 7 6 II.F. Chokes are used atiüit°ii.: 'Ggeitilit... :4ì''.'.'i ', h..1,'t::... }'» .....i_ . ne; and specified by several recognised designers owing to their amazing efficiency. MAGNUM Made in two ranges:- Standard type, 50 to BUILME-JONE 3,000 metres. MOVING -COIL SPEAKERS :.. u Short-wave type, from ô. CO. LTC., below 10 up to 100 incorporating B.T.H. Rice -Kellogg Units MAGNUM HOUSE metres. are now available. TELEPHONE: HOP 6257-8 Price Prices from 10s. Od. to £9 £45 288,BOROUGH HIGH ST. 7/6 Particulars on application. LONDON. S. E.1 .....; ...:.:K:.::: ......¡..¡ . :..;.:: r :.:.:: . r.!r// :: t:/.t.. ¡r:.^.:e:.:.:.:.::: ;:.:r:..,: :v.:.r:::: r.u:.ts: v.:: .t::::r::r.s::.: v..y:::: :::::t.T:..:: .::.... :'r:::.::..t1 ::::.:.:.:. :. ........."..._.r..., -_._ ....... 577 U www.americanradiohistory.com MODERN WIRELESS June, 1928 4151.40 4,N-- to Adair, ga otieat.a` Zbe aro o,a'' oloaa moirdC Ç óe ea1 n1,6012 aae. oávice áe' ,5e o`'` ír`` áa teQ ,D`75 op i3flHllr:>- o\4.- io a>>3 p `o ce, ` a, oe o a5 aales b1pp a5,a eete <'éoted`o %,0-i-lc,aa oe4ét. b tibeGla{ ew e NI' o or c 1 a r 5o 4 i4` jo4¢o`ye o oe toe Go# 27 I. C. t ossor, Ltd., Highhury Grove, N.S. The "JGr own " Mascot Loud Speaker Price - - £4 10 0 In the Argentine (land of the "Pampas") On the great cattle ranges the Only satisfies their taste. "Jl3t Wn " Loud Speaker is All the world over the treasured beyond price,it brings - 3Growne sets and maintains laughter and song to lonely the standard of Loud Speaker lives. In the cities too it is known reproduction. Wherever per, and valued, for the Argentines fection is required, there is a are a musical people; the best "JiCOwn. " Advt. S G Brown. Ltd.. Western Avenue. North Acton. London. WI (G7.) 2761 578 www.americanradiohistory.com June, 1928 MODERN WIRELESS The " Sydney Two De Luxe "-" Regional " Rumours-" Radiotic" Farmers The " Sydney Two De Luxe " most of the area at present served by the Daventry Experimental station, and a power of at least 25 kw. seems FEW sets have gained such rapid popularity as the indicated. " Sydney Two." Originally designed as a two - Even now, however, it must be remembered that the valve receiver for short-wave reception only, it Regional Scheme, as a whole, has not been sanctioned quickly became a " favourite " circuit, and thousands by the P.M.G. The next twin wave -length high -power of amateurs throughout the country have from time to station may be held up, just as the new North London time testified to the " Sydney Two's "- extraordinary one was, and many years may pass before the ten stations efficiency. are complete. That may seem a pessimistic view to take, Consequently, it is not out of place to give in this issue but experience has shown that when dealing with the of MODERN WIRELESS a de luxe version of this receiver, Post Office it is best and safest to take a pessimistic view. and we feel sure that the improvements made in this if, by some lucky chance, the scheme is proceeded with " M.W." version, together with the high reputation of But without undue delay, then in about four years' time the the set, will make it very welcome to our readers. ten Regional transmitters should be in full working order. This de version of the Sydney Two " has special luxe " meantime, amateurs and listeners-and especially features which should enhance its appeal. For instance, In the Captain Eckersley-will rejoice that at last a definite the de luxe model is suitable for reception of all wave- move can be made. lengths ; the set is not confined to the reception of stations operating only on the short-wave band. Constructors will also notice that the set is agreeably " Radiotic" Farmers free from hand-capacity effects on short-wave adjustments, "RAT." is the latest term used to describe people and that the system of reaction control is extremely who have been badly bitten by the " wireless smooth and free from those " threshold " noises which so bug." It has been coined by Mr. Geoffrey often completely ruin reception on so many short-wave Mitchiner, a young boy formerly of Croydon, Surrey, six sets. who emigrated with a party of juveniles to Canada Needless to say, we strongly recommend this " Sydney weeks ago. Mr. Mitchiner is a wireless enthusiast, and Two De Luxe "-hence its " starred " position in t his before emigrating asked the Canadian National Railways to make special efforts to place him with a farmer issue ! And as " M.W." is not in the habit of bawling officials exaggerated and super merits for every set it publishes who would co-operate with him in his wireless experiments.