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Potomac instruments sd-31 & rx-31 companion receiver
POTOMAC INSTRUMENTS SD-31 & RX-31 Companion receiver Fully tested !
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.
SD-31 Frequency Synthesizer and Coherent Detector
OUTPUTS: VAR Output and Control - varies output level at VAR connector for low level applications
LO Z - hight level output for connection to bridge for Z less than 180 ohms.
HI Z - high level output for connection to bridge for Z greater than 180 ohms.
BATT - indicates charge level of batter supply
LOCK - provides positive indication that output frequency is locked to crystal reference oscillator frequency
OUTPUT - indicates relative output of power amplifier
NULL SLOW - provides highly damped indication of coherent detector output.
NULL FAST - provides undamped indication of coherent detector output.
AM SWITCH: Selects internal (INT) or external (EXT) Amplitude Modulation of RF output
DET GAIN: Adjusts gain (sensitivity) of coherent detector
FREQ 100.0 - 1999.5 KHz: Sets synthesizer output frequency within indicated range with separate thumb sheel switches for each digit
F CONTROL: Enables operator to vary synthesizer output frequency slightly above or slightly below the nominal value
RX-31 The RX-31 is designed specifically as an RF interface between an impedance bridge and the SD-31 Coherent Detector.
100.00 - 1999.5 kHz switch selected, 500 Hz steps
.01% of frequency approximately
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
Internal: 40 Hz (approximately) square wave
External: 1.0 mV max. required to produce 50% modulation, 300 Hz - 3 kHz.
1 V RMS approximately across 100 K ohms for 100% modulation of receiver RF input at 40 Hz.
Detector null, fast or slow response
105-130 VAC, 50-60 Hz, 15 VA (when charging)
8 hours approximately after full charge depending on frequency and load.
16 hours (unit not in operation)
The RX-31 is designed specifically as an RF interface between an impedance bridge and the SD-31 Coherent Detector. Conveniently mounted in the protective cover of the SD-31, the RX-31 is a single conversion super heterodyne receiver which derives its local oscillator signal and power supply voltage from the SD-31. Receiver circuitry is packaged in an aperature-free, drawn aluminum enclosre which provides excellent RF shielding, IF selectivity is provided by active bandpass filters which limit receiver bandwidth to100 Hz.
