NORMAL OPERATION (cont)

TM 11-5820-917-13

display will flash and indicate the position of the MODE switch and not necessarily

the actual path being received at that instant in time. For example, if a path 2 sweep

was started in the program mode, the PATH digit would show a steady 2. If however,

during this sweep, the MODE switch was changed to the SET 3 position, the RCS-4B

would continue to receive path 2, but the PATH digit would display a flashing 3.

This serves to remind the operator that controls such as START, RESET, and

ADVANCE TIMER which affect the program timers are active and will control the path

3 clocks even though a path 2 sweep is in progress. This feature allows the operator

to initialize another path program timer while a sounding sweep is in progress without

disturbing the RF sweep. The frequency MHz display indicates the RF frequency

of the path being received regardless of the position of the MODE switch.

b. During normal operation the INPUT AT TEN switch should be in the "O" dB

position. Occasionally conditions of an unusually high background noise strength

will drive the CRT bargraph display of received signal strength (AGC level) off

scale and make interpretation of the received signal strength difficult. This condition

can be remedied by selecting 10, 20, or 30 dB attenuation of the received signal

by turning the INPUT ATTEN switch to the respective "10", "20", or "30" position.

The last received Chirpsounder records, one for each path, are stored in

three separate display memories. The DISPLAY switches select which of these

records will be shown on the CRT. The display memories are automatically updated,

independent of the settings of the DISPLAY switches. Thus, programmed soundings

(receiver sweeps) are independent of CRT display operation. Receiver sweeps are

determined by the path programmer only. Sweep activity is indicated by the LED

numeric display (MHz and path) and the CRT load line cursor which indicates the

instantaneous receiver frequency on the CRT display. The CRT DISPLAY controls

may be operated at any time with no effect on the receiver's sweep operation.

d. Up to six fixed cursors can be stored and displayed on the CRT. The movable

(left) and

(right) switches.

cursor is controlled with the CURSOR

The frequency setting of the movable (blinking) cursor is displayed on the digital

MHz readout when the CURSOR FREQ pushbutton switch is pressed. A fixed cursor

is positioned on the CRT by placing the movable cursor (using the CURSOR

, switches) at the particular frequency of interest and pressing the CURSOR

STORE switch. The fixed cursors remain stored and displayed for all sweeps and for

all path displays until erased. A fixed cursor is removed by placing the movable

cursor over the fixed cursor and pressing CURSOR ERASE switch.

Due to slight differences in the absolute frequency of the sounder transmitter

and receiver frequency standards, the Chirp sounder records will slowly drift up or

down on the receiver CRT. This drift requires an occasional manual slip adjustment

of the receiver synchronization to recenter the Chirp sounder record on the CRT.

If however, this manual slip adjustment is required more than once every eight hours,

the frequency standard should be adjusted (paragraph 5- 21) . The slip adjustment is

made with the receiver MANUAL SYNC controls as follows:

(1) Wait until the RCS-4B starts a sweep for the path to be recentered.

(2) Select the CRT display for the path to be recentered.

(3) Turn the MODE switch to the SET positon corresponding to the path to be

recentered, and set the SLIP RATE to 1 ms/sec.

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