Tips and Jottings

Radio Record, Volume III, Issue 50, 27 June 1930, Page 40

Tips and Jottings

NE little-known method of overcoming persistent humming interference is to bring a coil associated with the source of disturbance. close to the receiver, and arrange the coupling with the coil so that the effect upon the set shall be equal in intensity’: and opposite in direction to the disturbance. which is being picked up. op Pod * ALTHOUGH 2-megohm leak may be ideal for ordinary reception, on shert-waves this resistance value is generally too low, and 4, 5, 4, %, or even 8 megohms may be tried to increase sensjtivity. ; To many constructors and experi menters the. following tabie of capacities in parallel and in series will*

SOMETIMES a listener will unexe pectedly find his dry cell "A" batteries run down just when he requires them urgently, and when he is unable to procure new cells. A visit to a chemist’s shop, however, would save the situation. Here is,the formula :- First remove the outer cardboard covering of the dry cell, and then take some sharp implement and with it punch a number of holes in the exposed zine container. Now take a jar large enough to hold the cell and some liquid in addition. Take sal ammoniae 3 and water in the proportion of 20z. to; the pint and dissolve the chemical ix the water. When ready, place in the jar .with the old cell. Connect to the terminals as usual. This method will considerably prolong the life of cells which are not "too far gone" to rejuyenate, ,

pe ound useLul.-~ : Separate Combination Capacities. Series. Parallel. .0001 and 00025 .000071 00035 0001 and .0005 .000088 ~=s- .0006 0001 and .001 .000093 0011 0001 and ..005 .000095 .0021 0001 and .005 .000098 0051 0001 and .006 .000098 .0061. .00025 and .0005 -00016 00075 .00025 and .001 .0002 00125 .00025 and .002 .00022 .00225 .00025 and .005 .000238 .00225 .00025 and .006 .00024 .00625 0005 and .001 .000838 .0015 .0005 and .002 .0004 0028 .0005 and .005 .00045 .0055 .0005 and .006 .00046 0065 001. and .002 .00066 003 . 001 and _.005 .000838 006. 001 and .006 . 00085 — .007 002 and .005 .0014. Ristys 002. and .006 1115 005 and .006. .0027 OIL ed ve ss