724-B
The General Radio 724-B Precision Wavemeter was introduced in Catalog L (1948) and remained available through Catalog N (1954).
The Type 724-B is an absorption type wavemeter whose range is from 17 kHz to 50 MHz using seven coils with an accuracy of ±0.25%. The capacitor used is similar to the Type 722-N and its connection to the inductor is by the Type 774 coaxial connector. The primary application of the 724-B is oscillator and transmitter frequency measurement. Resonance is achieved using one of three methods, absorption method or reaction method and beat method. Using the panel microammeter the the absorption method is employed. Regardless of the method, once resonance is achieved its a matter of using the correct chart for the coil in use to determine the frequency. The Type 724-B is supplied as a collection of calibrated components sharing the same serial number. That is the capacitor, all the inductors, and calibration charts must have the same serial number to achieve the stated accuracy. The 724-B replaced the 724-A Wavemeter. The principle difference is the earlier version used a vacuum tube rectifier while 724-B uses 1N34 crystal rectifier. The "A" version required a battery, the "B" version does not. The wavemeter is furnished with wooden storage case, fitted with lock and carrying handle. This case has compartments for holding the capacitor, inductors, and calibration charts.
Specifications
- Frequency Range: 17 kHz to 50 MHz using seven inductors
- Accuracy: ±0.25%
- Inductors: 7 coils wound on steatite forms and enclosed in molded phenolic cases
- Capacitor: Precision worm-drive type similar to Type 722
- Resonance Indicator: microammeter and 1N34 crystal rectifier combination
