Johnson DM3474, Service Manual

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SECTION 1
1-1
Part No. 001-3474-002
GENERAL INFORMATION
1.1 SCOPE OF MANUAL
This service manual contains alignment and service information for the Johnson Data Telemetry (JDT)
DM3474 UHF High Specification Data Module Transceiver.
1.2 EQUIPMENT DESCRIPTION
1.2.1 GENERAL
The JDT DM3474 is a synthesized data transceiver (transmitter and receiver) which operates in the 403-512
MHz UHF frequency range. Transmitter power output is 2 watts nominal, and operation is simplex or half duplex.
Versions of the 3474 covered in this manual are indicated in Section 1.4. The 3474 has a frequency stability of
±
1.5 PPM (see Section ).
The number of channels that can be selected with the DM3474 model is determined by the customer supplied
synthesizer loading circuitry.
1.2.2 DM3474 SYNTHESIZER PROGRAMMING
The DM3474 requires customer supplied circuitry to load the synthesizer with channel information. The
protocol that this circuitry must follow is described in Section .
1.3 TRANSCEIVER IDENTIFICATION
The transceiver identification number is printed on a label that is affixed to the PC board. The following
information is contained in that number:
3474 2 A 1 4 3 A 12345
Model
Revision
Letter
Manufacture
Date
Week No.
of Year
Year
Plant
Warranty
Number
Eighth Digit
of PN
Range