THE WIRELESS WORLD AND RADIO REVIEW THE OFFICIAL ORGAN OF THE RADIO SOCIETY OF GT. BRITAIN Na 22. No. 18518 MARCH 3rd, I 9 2 3 WEEKLY CLVOL. XI. 3 " 5 M S." THE TRANSMITTING STATION OF THE MANCHESTER WIRELESS SOCIETY. NE has heard a good deal recently station 8 ALF, that he received signals from of the reception in this country, often a British station signing 5 MS. He gives the O with inferior or indifferent apparatus, time as 051I G.M.T., December Toth, of the transmis- and says signals sions of American were heard until amateurs. It is now about o514 G.M.T. reported that 5 M S The station (theC.W.transmit- sounded like D.C., ter built and Oper- `k but was broken up, aced by members giving the effect of the Manchester of rectified 25 Wireless Society) cycle A.C. QSS has been received was medium, he in. Pittsburg, says. L.S.A. Below is Wavelength of a copy of a letter about 270 metres. from Pittsburg re- = I regret the de- porting the recep- .. lay in forwardingg tion of signals. ° this information, (Copy of letter ad- y and trust that it dressed to Mr. F.H. will be of interest Schnell, Traffic +° ' ; * = to those concerned. Manager, Ameri- Very truly yours, can Radio Relay . t J. B. WESTERVELT League, from .7. B. à r (WX). Westervelt andj.H. ` JOHN LEIGHMER Leighmer.) (JL). Radio 8 ZD. One Manchester 5306, Westminster amateur has re- Place, ported having Pittsburg, Pa. heard American December 12, 1922. amateurs discuss- Mr. F. H. Schnell, The aerial. It is 80 ft. high and the masts are 120 ft. apart. ing by wireless Hartford, Ct. telephony the MY DEAR MR. SCHNELL, reception of the signals transmitted from 5MS. I have just learned from Mr. John Leighmer, When these reports are confirmed Man- operator JL of this station and operator of chester Wireless Society may stand credited s www.americanradiohistory.com 716 THE WIRELESS WORLD AND RADIO REVIEW MARCH 3, 1923 The Transmitting and Receivint Apparatus. with being the first to have their transmissions primary energy dealt with is something less received in America, and so it is thought a than r kW., so that the transformer is seriously short discussion of the transmitting apparatus overloaded. The approximate voltage be- will be of interest. tween the centre tap and the anodes of the It is pointed out here that credit should rectifying valves is 5,000. " U3 " type rectify- not be given so much for the actual transmission ing valves are used, a voltmeter being connected and reception of the signals as for the obstacles across each filament. and difficulties which have been overcome It is obvious that, given an ample supply before the station could be built at all, the of current, an efficient filter system should be chief difficulty being the electric supply, which employed, but this has to be sacrificed so as is roo volts 8o cycles, single phase. Lack to eliminate loss in chokes, the result being, of funds made it impossible to purchase probably, not pure C.W., which point was suitable transformers for this periodicity, so reported upon by the American amateurs recourse had to be made to the nearest available who received the transmissions. The oscilla- apparatus. The roo volt 8o cycle mains, ting circuit comprises two " T 450 " valves, supply energy to the high tension transformer, a tuned grid circuit, and a direct coupled rectifier filament transformer, and power aerial. The direct current high tension is valve filament transformer. Each transformer connected across a condenser, which is joined is provided with a centre tap. The high in the foot of the aerial system and passes to tension transformer is rated at 200 watts, the anode of the two valves in parallel from. roo volts to ro,000 volts, So cycles. The the A.T.I. and anode tap. The anode tap is www.americanradiohistory.com MARCH 3, 1923 THE WIRELESS WORLD AND RADIO REVIEW 717 variable to secure the best efficiency. The cage comprises six wires arranged round earth is connected with the centre points of suitable hoops, and is supported between the filament transformers, and to the grid masts 8o feet high and 120 feet apart. The circuit. The grid circuit comprises a coil lead -in is also in the form of the six wires coupled with the A.T.I., and is tuned with spaced round the small loops, and is taken a small variable condenser, the vanes of which from the electrical centre of the aerial. are widely spaced to withstand the voltage. The earth consists of a number of wires The grid condenser and leak are both variable buried in the ground at water level, and run and the key is arranged to connect or disconnect the whole length of the aerial. When the set the grid leak with the grid condenser. Addi- is properly adjusted, the aerial ammeter con- tional cells up to about 70 volts are connected nected in the aerial circuits reads 9 amperes, to provide more negative on the grids of the which is considered very good, observing that valves. the actual input is less than i kW. This par- Contrary to usual ideas about a direct ticular circuit when being experimented with coupled aerial not being conducive to sharp previous to the actual tests, and using the tuning, it was found in this instance that same apparatus, but with a D.C. supply of the reverse result was obtained owing to 2,50o volts, registered an aerial current of every part of the circuit being variable, enabling 12 amps., with an input of i kW. It has been very critical adjustments to be made. This decided to continue tests each Sunday, using point was particularly and favourably reported alternate stations 5 MS and 5 Mr, until upon by a good many members of the wireless further notice. Any reports will be appre- fraternity. The aerial is of the sausage type, ciated, and should be forwarded to the Hon. connected " T " fashion. The horizontal Secretary, Manchester Wireless Society, 2, Another view of the Transmitter. The mounting of the components permits of ample spacing and easy access to the high tension equipment which is assembled behind. www.americanradiohistory.com 718 THE WIRELESS WORLD AND RADIO REVIEW MARCH 3, 1923 Parkside Road, Princess Road, Manchester, of the transmitting valves. Also to Messrs. stating particulars of receiver, strength and Burndept, Ltd., for the advice given on various characteristics of signals. The wavelength technical points. Mr. J. H. Brown, Vice - will be as near 200 metres as possible. President of the Society, made success The thanks of the Society are due to the possible by providing the best facilities as Marconi -Osram Valve Company, and the regards accommodation for the complete Mullard Radio Valve Company, for the loan station. Notes on Rectified A.C. for Plate Circuits. By MORTIMER A. CODD. WHILE carrying out investigations In measuring the current at this point it on electrolytic rectifiers during the should be borne in mind that the usual moving past twelve months, certain ex- coil instrument cannot be used since the periments were tried with the view to employing current is pulsating and the instrument there- rectified A.C. to feed the plate circuit of one fore itself acts as a very efficient choke. or more valves. In this case a Paul vacuo- junction thermal In the first place it was necessary to ascertain milliammeter was used. the order of the current flowing in the circuit using the normal type of reception valves. The current from a 50 -volt dry battery in good condition was passed through a standard laboratory Weston milliammeter. Using up to seven valves, the current varied from I to 2 millamperes per valve, thus with three H.F., one rectifier and two L.F. valves the current used was from 8 to 12 milliamperes. This experiment is most instructive, the IRON CONTAINER variation in current with the different con- etc., being most illuminating. Fig. 1. The Electrolytic Rectifier and smoothing ditions of tuning, cireur. As the current required is so minute, quite a small rectifying cell will suffice. Fig t gives a diagram from which it will be seen In order to smooth out the rectified current that the " middle point " method of con- a choke was inserted in series as shown in nection is employed. the diagram, the value of the self induction 25 Probably Fig. 2 is an oscillograph of the voltage being of the order of henries. in each leg, curve taken directly over the rectifier. It will two smaller chokes, one inserted besides presenting be noticed that the lowest point of the rectified would give better results, wave is considerably above the zero line. a more symmetrical arrangement. This is due, possibly, to the capacity of the The condenser, as shown, was very necessary, aluminium electrodes which even when small the value being varied on trial from oI to have a very considerable capacity. to microfarads. The writer suggests this property may Quite good results were obtained with 0.5 adventitiously aid in smoothing the resultant microfarads, but 5 microfarads gave perfect current when passed through the series results. Fig. 3 is an oscillograph. of the choke coil. voltage curve of the filtered wave, so near to www.americanradiohistory.com 719 MARCH 3, 1923 THE WIRELESS WORLD AND RADIO REVIEW Fig. 2. Voltage as derived from the Rectifier with a 50 cycle supply. to present certain continuity as barely to be distinguishable This system seems for reception, but for from a straight line.