TM 11-6660-266-13
LORAN-C, VLF, or PTU Processor, as appropriate, and sent to the Main Processor in digital format. The LORAN-
C and VLF Processors perform wind computation and the PTU Processor computes meteorological values.
Operation of the UHF Receiver is controlled by the Receiver Processor, which executes commands received
from the Console Processor and sends receiver status data to the Console Processor. The Receiver Processor
uses a microcontroller for automatic tracking of the radiosonde frequency during launch and flight, and has two-
way communication with the Console Processor.
In the RDF mode, PTU data received from the RDF Antenna bypasses the UHF Receiver and is filtered,
processed, and sent to the Main Processor. RDF antenna position data is a direct input to the Main Processor.
The MARWIN Processor contains two types of Built-In-Test (BIT) which are: power-up tests and diagnostics
tests. Power-up tests are automatically initiated when power for the MARWIN Processor is turned on and also
after reset. Each microprocessor module also contains individual BIT programs which are independent from
other module BIT programs. BIT operation is controlfed by the Main Processor and starts with a test of the front
panel console. After the console self test has passed, tests continue at the system level during which the Main
Processor starts its own internal test program, collects the results received from the other processor modules,
and produces warnings or error messages as necessary. The built-in-test process can he observed on the front
panel LED indicators. In general, a flashing OK LED indicates passing of the test, a flashing ERR (error) LED
indicates errors have been identified during the test, and the I/O LED indicates data transmission.
The diagnostic tests ensure that the individual modules are operating properly and serve as a tool for fault finding
and repair to the module level. This allows for most Unit level and Direct Support level troubleshooting of the
MARWIN Processor to he carried out without the use of special tools or test equipment.
For more detailed information, refer TM 11-6666-280-10, TM 11-6660-280-24-1, and TM 11-6660-280-24-2.
1-9-3. RDF Unit. A8 (Figure 1-4). The RDF Unit consists of four major components: an Azimuth Unit, an
Elevation Unit, a hand-held Control Display Unit (CDU), and a Tripod Assembly. The Azimuth Unit contains the
Azimuth Shaft Encoder, the Azimuth Drive, the Tracking Board, the Control and Data Processor, and Filters. The
Elevation Unit contains the Monolobe Scanner, the AM and FM Receiver, the Elevation Shaft Encoder, and the
Elevation Drive.
Within the Monolobe Scanner is an array of four dipole antennas which are connected to a network of sum and
difference hybrib junctions. The hybrid network provides three signals: (1) a summed signal from ail of the dipole
antennas, (2) an azimuth difference signal, and (3) an elevation difference signal. The two difference signals are
sequentially and alternately combined with the sum signal to provide a composite signal for connection to the
AM/FM Receiver. The single RF output signal from the Monolobe Scanner contains the original radiosonde
frequency modulation (FM) and amplitude modulation (AM).
The AM/FM Receiver is of dual conversion heterodyne design. Automatic Frequency Control (AFC) circuits act to
maintain receiver tuning at the radiosonde transmitted frequency. Automatic Gain Control circuits (AGC) act to
compensate for the variation of the strength of the radiosonde signal during the sonde flight. The receiver
contains both FM and AM demodulator circuits. Radiosonde PTU FM modulation is demodulated, conditioned,
and amplified in the receiver before application, through the Filter, to the MMS MARWIN Processor as PTU data.
Azimuth and elevation difference signals (AM) are detected and the resulting tracking error signals are directed
respectively to azimuth and elevation servo circuits on the Tracking Board.
The servo circuits amplify and condition the tracking error signals detected by the Monolobe Scanner and
developed by the AM/FM Receiver. The amplified error signals are applied, through Azimuth and Elevation Drive
Amplifiers, to the Azimuth and Elevation Drives which move the RDF Antenna in the appropriate direction to
reduce the tracking error signals to zero. As the radiosonde moves, the servo circuits continuously make the
necessary corrections to track the sonde, and thus the RDF Antenna is continuously pointed exactly towards the
transmitting radiosonde.
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