A Synthesizer-Detector providing a high output crystal signal generator of precisely known frequency combined with a sensitive, selective detector for RF bridge measurements of AM antenna impedance.
The Model SD-31 Synthesizer-Detector is a high output crystal signal generator of precisely known frequency combined with a sensitive, selective detctor for RF bridge measurements of AM antenna impedance. Packaged in a single light-weight battery-powered unit, the SD031 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 ofload 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 for detection a coherent detector which rejects interfering signals picked up by the antenna. In this arrangement, the generator is mudulated 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 witht eh 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.
|Frequency||100.00 – 1999.5 kHz switch selected,
500 Hz steps
|Frequency Accuracy||±005. +200°F to +1000°F|
|Frequency Vernier (AF)
|±.01% of frequency approximately|
|Output Levels||HIZ: 20 V RMS with 1000 ohmload (use
for Z>180 ohms)
LOZ: 8 V RMS with50 ohm load (use for Z<180 ohms)
(HIZ & LOZ: minimum levels with fully charged battery)
VAR: 100 mV RMS approximately with 50 ohmload
|AM Modulation||Internal: 40 Hz (approximately) square
External: 1.0 mV max. required to produce 50% modulation, 300 Hz –
|Detector Input Requirement
(from external receiver)
|1 V RMS approximately across 100 K
ohms for 100% modulation of receiver RF input at 40 Hz.
|Metering (Switch Selected)|| Battery voltage
Phase loop locking
Detector null, fast or slow response
|AC Power Unit||105-130 VAC, 50-60 Hz, 15 VA (when
|Dimensions||Height – 9 1/2 inches
Width – 11 1/2 inches
Depth – 6 1/2 inches
|Battery Operation Time||8 hours approximately after full charge
depending on frequency and load.
|Battery Operation Time||16 hours (unit not in operation)|
Specifications subject to change without notice.