CROSSTALK AND NOISE FEATURES 



149 



pletely balanced out when the coil is adjusted. The turns of conductor 

 in the Fig. 5 coil are so located that this side-to-side capacitance un- 

 balance is less than 5 micro-microfarads. The capacitances between 

 wires of either the primary or secondary winding do not affect the 

 unbalance but contribute a part of the capacitance loading which 

 compensates for the line inductance of the coils. 



In the actual balancing coil, shown in Fig. 6, the windings are located 

 in channels cut in a fibre tube which is secured to a head carrying the 

 winding terminals and a bushing through which passes the threaded 

 brass rod supporting the two cores. Below the head are small spool 



Fig. 7 — Arrangement of inner winding of trial balancing coil. 



forms on which the shunts are wound. Insulating material such as 

 bakelite is used to obtain proper spacing of the two cores. 



The rather unusual manner in which the turns are applied is illus- 

 trated in Fig. 7, which is a closeup view of the two wires forming the 

 inner winding. These two wires alternately cross over each other, 

 progressing along the axis in opposite directions of rotation. The 

 outer winding is similarly applied. This type of winding eliminates 

 all splices within the coil, removing hazards incident to interior splices. 



The complete coil assembly is enclosed by an aluminum container 

 which serves the dual purpose of a shield and a convenient means of 

 holding the coil for mounting purposes as this container fits snugly into 



