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SD-31 Frequency Synthesizer
and Coherent Detector
PDF Brochure |
INTRODUCTION
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.
Click
here for a full view of the Block Diagram.
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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.
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METER FUNCTION SWITCH:
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.
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AM SWITCH: Selects internal (INT) or external
(EXT) Amplitude Modulation of RF output
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DET GAIN: Adjusts gain (sensitivity) of coherent
detector
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FREQ 100.0 - 1999.5 KHz: Sets synthesizer output
frequency within indicated range with separate thumb sheel switches
for each digit
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F CONTROL: Enables operator to vary synthesizer
output frequency slightly above or slightly below the nominal value
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RX-31 RECEIVER OPTION
The RX-31 is designed specifically as an RF interface between an impedance
bridge and the SD-31 Coherent Detector.
Click here for details >> |
| SD-31
SPECIFICATIONS |
| Frequency |
100.00 - 1999.5 kHz switch selected,
500 Hz steps |
| Frequency Accuracy |
±005. +200°F to +1000°F |
Frequency Vernier (AF)
Adjustment Range |
±.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
wave
External: 1.0 mV max. required to produce 50% modulation, 300 Hz -
3 kHz. |
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
Output monitor
Detector null, fast or slow response |
| AC Power Unit |
105-130 VAC, 50-60 Hz, 15 VA (when
charging) |
| Dimensions |
Height - 9 1/2 inches
Width - 11 1/2 inches
Depth - 6 1/2 inches |
| Weight |
12 lbs. |
| 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.
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- 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
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