Transmission-line balance indicator for transmitters
14 June 1951
The instrument is intended for use with a 2-wire line fed from an Alford network. Two equal capacitors are connected in series across the lines and the centre point is taken to the live side of a parallel resonant circuit, tunable to the transmitter frequency, the other side being earthed. This tuned circuit feeds a rectifier galvanometer through an adjustable potentiometer. Balance is indicated by zero or min. reading on the galvanometer and the Alford network can be adjusted to give this. The indicator, which is portable, is in the form of a box 5frac12times8frac14times4frac14 in with two h.v. bushing insulators at the top. Its weight is 4 lb and it covers the range 4-30 Mc/s.