User Manual

1-1
August 1997
Part No. 001-3412-002
SECTION 1 GENERAL INFORMATION
1.1 SCOPE OF MANUAL
This service manual contains alignment and ser-
vice information for the Johnson Data Telemetry
(JDT) DM-3412 UHF Synthesized 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 (Part No. 001-3240-001) and the
Modem boards (Part No. 001-3276-001/001-3296-
001) should be referenced for the users specific con-
figuration.
1.2 EQUIPMENT DESCRIPTION
1.2.1 GENERAL
The JDT DM-3412 is a synthesized data trans-
ceiver (transmitter and receiver) which operates in the
380-512 MHz UHF frequency range. Transmitter
power output is 5 watts nominal at 13.3V DC in sim-
plex or half duplex modes.
Versions of the DM-3412 covered in this manual
are indicated in Section 1.5. The DM-3412 has a fre-
quency stability of ± 1.5 PPM (see Section 3) and is
available with or without the Loader/Modem boards.
The number of channels that can be selected with
the DM-3412 model is determined by the customer
supplied synthesizer loading circuitry. The
DL-3412 model is 8-Channels when supplied with the
DL-3240 Loader board, the DL-3276 modem kit or
the DL-3296 modem kit.
In addition to this UHF 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 and Industry Canada 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 Interna-
tional 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 DL-3412 WITH LOADER BOARD
The DL-3412 (Part No. 242-3412-xxx) can be
ordered with the 8-channel Loader board (Part No.
023-3240-001). The Loader board performs synthe-
sizer loading through an RS-232 DB-9 interface. In
addition, this board has circuitry which provides elec-
tronic control of the following:
Transmit/Receive data conditioning and gating
Carrier Detect
Power Control
Modulation Flatness
Audio/Data Filtering
Sleep/Wake-up to minimize current consumption
Diagnostics that includes:
Input Voltage Sense
Input Current Sense
Ambient Temperature Sense
RSSI Indicator (RSSI Sense)
Forward/Reverse Power Sense.
The gating circuits allow user selection of data
filtering (standard or wide band) and also pre-empha-
sis/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.
NOTE: The synthesizer must be loaded each time
power is turned on. Therefore, one loader board or
customer supplied programming circuit is required for
each data transceiver.