Tips and Jottings

Radio Record, Volume V, Issue 22, 11 December 1931, Page 13

Tips and Jottings

QNE advantage of using enamelledcovered wire for coil-winding is that it is impervious to damp, and does not absorb moisture like silk and cotton coverings. A QUARTDR of a pound of No. 24 s.w.g. d.ac. wire has a length of fifty yards, two feet, three inches. A QUARTER of a pound of No. 26 d.s.c. wire has a length of 812 yards. SETS which employ only one highfrequency stage can often be screened effectively by one upright screen. But when two rf. stages are

employed it is usually necessary for much more elaborate screening to be used. NAMELLED covered wire is quite satisfactory for coil-winding so far as insulation goes, but it results in a coil of rather high self-capacity. © F radio-frequency. yoltages or cur- " yents are present in the ‘audio stages of a receiver the result will be a peculiarly unpleasant form of distortion. {[® is not generally realised that two r.f. chokes in series may be used instead of one with advantage in many cases when instability due to insufiicient r.f. choking is suspected. WING to the large magnetic field surrounding it, the correct spacing of the r.f. choke from other components is of the utmost importance. | O not place your loudspeaker lead underneath the set, or in close proximity to the aerial or earth leads, as this is a common cause of unwanted ‘interaction and audio instability. ASBESTOS tiles, as used for roofing, make excellent rests for soldering irons. [ you keep your "A" battery inside the set’s cabinet, see that flex: leads do not touch it, as its acid will play havoc with the insulation. BEFORE trying elaborate choking arrangements to cure humming noises make sure they are not due merely to the aerial or earth leads being too close to electric light or power wiring.