Making the most of your receiver Eddystone Stratton VK7AG 0013
Recognised text
Text below was produced by optical character recognition and may contain errors. Check it against the original.
calling for renewals. dirty. If the machine is found to be in good condition bu If other equipment, the contacts may be worn or t still producing inter- ference, it becomes necessary to fit a suppressor, either across the terminals of the offending unit, or in series with them, depending on the type of suppressor employed. The simplest takes the form of a single condenser, connected as shown in Fig. 14. It is difficult to specify a definite value of capacity, since what may be correct in one instance may not be entirely suitable in another. An average value is 0. uF but other capacities between 0.01 and 0.5 uF should be tried, if possible. Where the interference occurs on short waves, the addition of mica condensers, having values between 0005uF and .005uF may improve matters. ACROSS TERMINALS WITH —4 CENTRE EARTHED. Fig. 15. An improved way of suppressing interference— two condensers in series with the centre earthed. TWO CONDENSERS IN SERIES The alternative arrangement, illustra- ted in Fig. 15 and using two condensers in series, with the centre earthed, usu- ally proves very effective, provided the earth lead can be made short. Whilst a common type of electric fan is indicated, the same principle (of connect- ing condensers) can be applied to other electrical equipment, of larger or smaller size. The voltage rat- ing of the condenser is important. It should be not less than 500 volts D.C. working, under any circumstances, and if the mains are 200/250 volts A.C. the condenser should be rated at not less than 600 volts A.C. working. More elaborate suppressor units are available for cases where the inter- ference is severe and not completely amenable to the relatively simple methods outlined above. These units are larger, and incorpo- rate various combinations of condensers and chokes. Where large machines are concerned, the current rating becomes an important factor, and since some disturbance of the mains wiring is called for, it is recommended that the services of a skilled electrical or radio engineer be utilized, in such cases. For preventing mains-borne interference enter- ing a receiver via the connecting lead, the specially developed Eddystone Mains Filter Unit (Cat. No. 732) will be found of value. It is efficient and reliable, and can be fitted between the plug on the receiver lead, and the mains socket, without special tools or expert knowledge. This Filter Unit is suitable for use with any Eddystone receiver, or, as far as that goes, with any receiver the line current of which is not greater than 0.5 amperes. It can be used with mains of voltages up to 250, either A.C. or D.C. Page Twelve Fig. 16. The Eddy- stone Cat. No. 732 Filter Unit—useful for placing between the mains and a receiver which suffers from local electrical inter- ference.