NUMBER OF TURNS

Dominion, Volume 26, Issue 97, 18 January 1933, Page 6

NUMBER OF TURNS

Condenser Combinations

People often wonder why it is that’ the usual values for the tuning condenser and eoil are .0005 mfd. and 50 turns respectively. There is no special reasou why the values should be exactly these and, as you know perfectly well, the circuit can be made to respond to the same frequency if the coil is altered, provided the condenser is altered to correspond. In other words, you can make various oscillatory circuits having the same natural frequency with an infinite range of values of coil and condenser, or perhaps I should say, of inductance and capacity; but, in each case, a change of the one necessitates a change of the other.

In point of fact, the ordinary 50 coil is convenient and has become standardised probably more or less by accident —like the speed of gramophone records and many other things—and with this coil and a .0005 mfd. condenser we can cover a range of, roughly, 200 to 500 metres wavelength, which is handy for broadcast reception. With a 75-turn coll and about ,0003-mfd. condenser, roughly the same sort of wavelength range would be covered.