User Manual

1-1
June 1997
Part No. 001-3492-001
SECTION 1 GENERAL INFORMATION
1.1 SCOPE OF MANUAL
This service manual contains alignment and ser-
vice information for the JDT DM3492 900 MHz Syn-
thesized Telemetry Unit.
This manual concentrates on the RF section of
the data link which may be paired with an internal
Loader board or 9600 baud Modem board.
Service manuals addressing items specific to the
Loader board (001-3240-001) and the Modem board
(001-3276-001) should be referenced for the users
specific configuration.
1.2 EQUIPMENT DESCRIPTION
1.2.1 GENERAL
The JDT DM3492 is a synthesized data trans-
ceiver (transmitter and receiver) which operates in the
928-960 MHz UHF frequency range. Transmitter
power output is 1-5 watts, 5W at 13.3V nominal, and
operation is simplex or half duplex.
In addition to this 900 MHz radio, JDT has a full
line of radios and radio modems to meet wireless data
communication needs. Both OEM RF decks and com-
plete FCC type approved radios and radio modems are
available from 132-174 MHz at VHF, 380-512 MHz
at UHF and 928-960 MHz at 900 MHz in both 5W and
2W units (VHF and UHF). High Specification units
are available to meet International requirements and
bandwidths to meet U.S.A. refarming requirements.
To learn more about the other JDT products, call 1-
800-992-7774 or 1-612-890-8155 to speak to a sales
representative.
1.2.2 DL3492 WITH LOADER BOARD
The DL3492 (Part No. 242-3492-5x0) includes
the 8-channel Loader Board (Part No. 023-3240-001),
which performs synthesizer loading through an
RS-232 DB-9 interface. The Loader Board has cir-
cuitry which provides electronic control of the
following:
l Transmit/Receive data conditioning and gating
l Carrier Detect
l Power Control
l Preselector Tracking
l Modulation Flatness
l Audio/Data Filtering
l Sleep/Wake-up to minimize current consumption
l Diagnostics that include:
Input Voltage Sense
Input Current Sense
Ambient Temperature Sense
RSSI Indicator (RSSI Sense)
Forward/Reverse Power Sense.
The gating circuits allow the type of data filtering
to be selected (standard or wide band) and also pre-
emphasis/de-emphasis to be enabled or disabled.
This board is programmed using an IBM

PC or
compatible computer and the Johnson Data Telemetry
programming software. Programming information is
stored by an EEPROM on the Loader board. Refer to
Section 3.3 for programming information.