The Potomac SD-31 Synthesizer-Detector is a high output crystal signal generator of precisely known frequency combined with a sensitive, selective detector for RF bridge measurements of AM antenna impedance. Packaged in a single light-weight battery-powered unit, the SD-31 complements bridges such as the General Radio 1606, 916, and the Delta OIB-1.
A frequency synthesizer determines the generator frequency, which can be adjusted in 0.5 KHz steps by means of a front-panel switch from 100.0 KHz to 1999.5 KHz. Frequency accuracy is the same as that of the internal reference oscillator. A front panel fine-frequency control varies the frequency up to ± .01 percent. The generator can drive a wide range offload impedance at levels up to 20 volts RMS. It also has a variable low-level output suitable for driving a counter or for receiver frequency calibration.
The SD-31 uses a coherent detector that rejects interfering signals picked up by the antenna. In this arrangement, the generator is modulated at a low frequency, and the SD-31 detector circuit responds only to a signal having that particular modulation. A sensitive and selective receiver connected to the bridge detector output is required; this can be the Model RX-31 Receiver, available as an option with the SD-31, or an external receiver such as the Potomac Model FIM-21 Field Strength Meter. The optional RX-31 Receiver is designed to work with the SD-31 and is automatically tuned to the generator frequency. The SD-31 is powered by a rechargeable battery adequate for 4-8 hours of use between charges. Battery recharging is possible while the unit is operating.
• Designed for Antenna impedance measurements with RF bridges in the presence of strong interference
• High-level oscillator compatible with General Radio 1606 Series, 916 Series, and Delta OIB-1 Impedance Bridges
• Frequency crystal controlled, variable in 500 Hz steps from 100.0 kHz to 1999.5 kHz
• Versatile - can be used as an RF signal generator for trouble-shooting antenna systems; as a variable frequency oscillator for antenna site survey; or other applications requiring a precise frequency source
• Special Coherent Detector circuit rejects interfering signals experienced during antenna measurements
• Receiver for Detector can be external or optional built0in RX-31 Receiver
• Powered by rechargeable batteries
• Self-contained portable package
