Maintenance Manual

MAINTENANCE MANUAL
RT-1601 RECEIVER-TRANSMITTER
815 Broadhollow Road 631-755-7000
Farmingdale, N.Y. 11735 FAX [phone]
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used. The R-T unit first local oscillator operates at 9401.3-MHz to convert the standard 9375-MHz
signal to a 26.3-MHz intermediate frequency. The same first local oscillator converts the 9310-MHz
transponder signal to 91.3 MHz. The 91.3-MHz signal is amplified by the preamplifier and the 91.3-
MHz I-f amplifier, detected, and then applied to the video-detector buffer.
5. Detailed Theory of Operation
A. Power Supply
(1) General (See figure 1.)
The power supply for the R-T unit converts +28 Vdc into the dc voltages needed for unit
operation: +23V, +6V, +15V, -20.5V and –330V. Two series transistors mounted on the
main frame are driven by the power supply circuits to provide regulated -23 Vdc. An
overload circuit in power supply limits current. Since +28 Vdc is continuously applied to the
R-T unit, a power supply on-off switch circuit is used to control R-T unit operation in
response to demands from the radar indicator. All voltages except the +23 Vdc are
developed by chopping the +23 Vdc, then transforming, rectifying, and filtering the chopped
voltage. The high voltage control and overload circuit, in addition to protecting the high
voltage ac-dc converter from overload, provides the trigger enable signal. Trigger enable is
generated after a 80-second, turn-on delay from the time-delay circuit, and is used to
switch-on –330 Vdc to the magnetron modulator as well as to enable the modulator trigger
on the mode decoder board. A fan is provided for cooling the power supply.
Figure 1 POWER SUPPLY BLOCK DIAGRAM