Synchronising Dial Readings

Radio Record, Volume III, Issue 19, 22 November 1929, Page 32

Synchronising Dial Readings

An Advantage in Set Operation

qz is of the greatest assistance for ; rapid and successful searching for distant stations if the dials of all tuned: circuits are exactly in step, or as nearly se as possible, over the whole range. If one "lags" a little behind the other, the amount of the. difference being fairly constant over the whole tuning range, it is possible to obtain almost, if not quite, the same readings at aly settings. The method is as follows. , Tune in a station whose dial reading is at about.the middle of the scale (in the neighbourhood of 50 on a 0-100 dial or of 90 on one marked'in degrees from 0-180). Now. loosen the dial of the lagging condenser so that it no longer drives the spindle and rotate it until the readings correspond exactly. After this the dial is tightened up again and it will be found that, over the major part of the scale at any rate, the two sets of readings at very close together, Still closer agreement between sets of condensers can. be obtained by’ the use of logarithmie condensers. The process of setting, the dials is the same as that just described, and once this has been carried out it will be found,. that the differences-over the whole range are usually minute. So closely. do the dials correspond that it is often possible to dispense with one of them and to "gang" two or even three condensers, driving them all with a common dial. In very sharply tuned circuits fine adjustments can be made, after the tuning has been done roughly, by means of midget condensers in parallel with each main condenser.