DRY CELL TO CRYSTAL SET

Radio Record, Volume I, Issue 5, 19 August 1927, Page 5

DRY CELL TO CRYSTAL SET

-_-_-_- A correspondent writing from Auckland asks if there is any way of coupling a Columbia dry-cell to 4 crystal set. It is not usual to employ local potential on orditary crystals, except in the case of carborundum, which give a sinall increase of volume and extra clarity when a bias of about one and a half volts is applied and controlled by means of a potentiometer of high resistance. ‘There is a method of causing a@ crystal to oscillate by applying a voltage of about 12 volts in a suitable circtiit, and the ‘crystal then behaves very much in the same way as a valve and.a crystal amplifier can also be added, but such amplification is not equal to that obtained from a valve, and these circuits need a deal of experiment and very careful handling, An article on the subject will be published _#€ a sufficent number of readers ere -interested to the extent of writing in ‘and asking for it. t --