Tips and Jottings

Radio Record, Volume III, Issue 18, 15 November 1929, Page 30

Tips and Jottings

Aerial ‘Pulleys. F a pulley is used at the top of the aerial mast for the halliards to run through, it can be the:-cause of a eonsiderable amount of inconvenience. Owing to its being so exposed to the weather the metal pulley is apt to jam or to break in time through the effects of corrosion, and it not. infrequently happens that the supporting rope slips from the groove in the wheel and becomes wedged between it and one of the sheaves. : A practice which avoids all trouble of this kind is to make use of a large shell insulator instead of a pulley. The ropes pass with. very little fricton over the polished surface .of the porcelain . and it is practically impossible -for..a

jam of any kind to occur. ‘The only calamity that may possibly hapnppn is that the insulator: may be broken by coming into violent contact with the mast if the aerial is let down thoughtlessly with a run. There need he -no fear of this happening if a pad made of old sacking is fixed to:the mast at the place where the insulator’ will come into contact with it when: the halliards are slackened. . Setting Variable Condenser Dials. ‘OR the panels of a receiving. set to present a neat appearance, it is necessary: to .set .the dials. of the variable condenser ‘on their spindles without.a wide gap between their. rims and the surface of the panel. This also makes it easier to take accurate readings of dial settings, since the scale passes close to the indicator. It frequently happens, however, that the dial, if set too close, scrapes on the el and becomes awkwardly stiff to tatns This difficulty may be obviated in a simple manner, by glueing a ring of thin felt or plush to the underneath of the dial, inside the, raised rim. If necessary, thin card' rings are first glued to the dial, so that the surface of the felt projects slightly above the raised part of the rim. The. dial may then be set down quite firmly against the panel, and it will be found that-the condenser has acquired a delightfully "silky" feel round the whole of its scale, An Improved Choke. T sometimes happens that one has on hand an audio-frequency transformer, which, save: for a burnt-out primary. winding, is undamaged in’ all other respects. It may. be desirabié to add a stage of choke-coupled audiofrequency to an existing set, or perhaps to experiment with this form -of coupling for the first time. The secondary. winding of most audio-frequency transformers’can be used as a substitute for a specially manufactured choke by connecting it up in the conventional manner, ; In cases where the primary winding of a transformer is burnt out while a set is working, a few changes in the connections will quickly enable the set to be used again as a choke-coupled receiver. It should be remembered that the valve, in whose anode circuit the choke is connected, should be preferably of the resistance capacity or special radio-frequency type to ensure the best results. One-Hole Fixing. .-, O not assume that: because a tomponent is of the- one-hole-fixing type one side of it is necessarily connected to the fixing bush. For instance some "on and off" switches have two soldering tags. at the back, neither of which is connected to the metal knob which controls the switch. Failure to notice such points. may lead to mysterious faults. Sereening by ‘Telephone. Wites. [ telephone wires are parallel, or almost parallel, with an aerial, they screen it to some exteat, and thereby reduce its practical: efficiency. In the case of transmitting aerials induce currents may be set up in the teleph#ne wires, and telephone subseribers have been known 'to overhear ‘the transmissions. If the aerial can be erected as nearly as possible at right angles to the telephone wires, the effect of the latter is. reduced -to..a..minimum,