Making the most of your receiver Eddystone Stratton VK7AG 0009
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PROTECTION FROM LIGHTNING AND STATIC DISCHARGES. In temperate climates, only very rarely is trouble experienced with light- ning, but it should be appreciated that an aerial can collect static electricity, particularly during hailstorms and thunderstorms. No ill effects are likely when a metallic path to earth exists, as will be the case with many receivers. With some, however (e.g., the Eddystone ‘‘670’’ marine Receiver), a condenser is interposed in the aerial circuit and the aerial proper is then highly insulated and is liable to attain an electric charge of quite a high value. In the tropics, thunderstorms are frequent and there is a greater liability to both lightning discharges and to the collection of static electricity. A number of devices are available which give simultaneous protection against lightning and static. One is the Belling-Leé.type L.350, which consists of carbon blocks separated by a mica ring, the assembly being mounted in a sealed glass tube, provided with wire connections. On a larger scale is the Ediswan Gas Discharge Protector, two types of which exist. One will pass surges of more than 20 amperes, the second and smaller one surges up to 5 amperes. It is important, with any form of lightning arrester, to connect one electrode to a good low resistance earth. MAINS CONNECTIONS. Advice regarding mains connections will be found in the handbook or folder which accompanies your receiver. It is desirable to emphasise that proper time and care should be taken over connecting your set to the mains in order that no loose connections will cause noise or any other difficulties. The first operation is to see that the voltage adjustment panel is correctly set and, of course, this should be done before the receiver is in any way con- nected to the mains. The I10 volts point is for use with mains between 100 and 110 volts, and no harm will accrue should the mains be of a value below 100 volts, as may be found on board a ship. Where the mains are between 200 and 250 volts the voltage adjustment plug should be inserted in whichever socket is marked with the value nearest to the actual mains voltage. It is very important, before connecting an A.C. mains operated receiver to the supply, to ensure that the latter is definitely A.C. and not D.C. Should it be D.C. no dial light will show and the receiver may be seriously damaged. With an A.C. set, it is immaterial which way round the mains plug is inserted. With an AC/DC set, however, it may be found that a rough sort of hum occurs in one position, in which case, it is only necessary to reverse the mains plug when, in practically every case, the hum will disappear and reproduction will be entirely normal. Also, when connecting an AC/DC or DC set to D.C. mains, the dial light may glow but no sound will be heard. In this case, again, the mains plug must be reversed so that the correct polarity is applied to the receiver. CARE OF BATTERIES. It should be appreciated that the excellence of the performance of a battery operated receiver depends to a large extent on the state of the batteries used with it. It pays in the long run to give these batteries proper attention, both from the point of view of obtaining long life and of securing the best possible performance from your receiver. The modern lead acid cell can be purchased in several forms. When the container is of glass or celluloid, the plates are visible and one can see at a glance by their colour the condition of the cells. When well charged, the positive plate should be a rich chocolate colour and the negative plate a light grey colour. When the grey becomes dark and when the chocolate colour becomes a lighter shade of brown it is an indication that the time has come to recharge the cell, Other cells are constructed in bakelite cases and it is then not so easy to determine the actual state by immediate inspection. A small volt meter is always a handy thing to have by one, as it is a fairly reliable indication of the state of the accumulator. Normally, a reading of between 5.9 and 6.2 volts on load should be obtained, but as soon as it drops below 5.9, the accumulator should be charged. A reliable method of judging the state of the accumulator is to use what is known as a Hydrometer, available in various sizes. With this instrument a sample is taken of the acid inside one of the cells, and providing a reading of Page Eight 1.15 is obtained, or below this, then cha a specific gravity of There are two i: battery. One is tha where visible, but in The second point is great degree or to I soon as you become put the battery on | Eddystone batte for all normal require length of cable be fo minimise voltage dre The top of the a with ordinary vaselin the accumulator is b the cell is being char process. .Normally, when distilled water. Car of any acid, as it wi comes into contact. From time to tir in order to remove might result in a part lator will not hold i lower voltage than t This washing ou such as a garage or should be in a fully ct gravity of the latter An accumulator not exposed to direct inside the cells. LOUDSPEAKERS Because compact Eddystone receivers, to suit personal req: An output trans’ as standard in Eddys of all types—comm broadcast. The sece is brought. out to sockets, and a loud-sp ed to the latter, s impedance of betweer No matching transfor with an external lou The Eddystone trated here is Zins: 0} and takes the form aluminium housing, a Sins. speaker unit an acoustic baffle. Thre available—black (Ca brown (Cat. No. 6 (Cat. No. 698), with f chromium plated feet This speaker is for use with an Eddy (communications 0