SYNCHRONIZATION WITHOUT PREDETERMINED SWEEP TIMING

TM 11-5820-917-13

c. Press and hold down the DISPLAY TIME-PATH 1 button. The LED clock dis-

play will show path 1 timing while path 2 indicator continues to flash.

d. When the (PATH 1) clock display advances to the desired delay offset (for

example 4 seconds), press START. This will start the PATH 2 clock.

e. Release the DISPLAY TIME PATH 1 button and note the PATH 2 clock has just

started. To check the delay offset between path 1 and path 2 timing, alternately

press and release the DISPLAY TIME-PATH 1 button and the clock display will alter-

nate between path 1 and path 2 timing so that a comparison can easily be made.

f. Set MODE switch to SET 3 and repeat above procedure to set PATH 3 clock

relative to PATH 1.

Place MODE switch to PROG position when finished.

3-15. SYNCHRONIZATION WITHOUT PREDETERMINED SWEEP TIMING. The following

method can be used if there is no opportunity for prearranged timing or operator con-

tact.

s. The TCS-4 transmitter sweep is started at maximum power at any arbitrary

time and is set to sweep every 5 minutes at a prearranged sweep rate.

b. The RCS-4B receiver operator, using a standard sideband HF receiver,

monitors a clear voice bandwidth channel on a frequency that typically propagates

for the time of day. (For paths less than 1000 km, 2-6 MHz at night and 4-10 MHz

during daytime should be satisfactory; for longer paths, frequencies 1.5 to 2.0 times

higher can be used.) The operator listens for the characteristic "chirp" sound

resulting when the transmitter signal passes through the received bandwidth. For

a 100 kHz/second sweep, the chirp sounder signal remains in a 3 kHz channel only

30 milliseconds and sounds like a very brief whistle or sliding pitch tune. For 50

kHz/second sweep, the sliding tone can be heard for at least 60 ms and the monitoring

process is easier.

c. When the receiver operator believes he has heard a chirp signal pass through

his channel, he notes the time and monitored frequency and then tunes to another

clear channel 1 MHz higher. For a 100 kHz/second sweep, the chirp will be heard

exactly ten seconds later; for a 50 kHz/second sweep, a 20 second period is required.

If the chirp is heard again, the second frequency and time are noted.

d. If no chirp is heard, the operator retunes to the original clear channel and

waits to see if the same chirp-like signal is heard exactly 5 minutes later. If the

chirp signal is heard at the appropriate time, it is recommended that the operator tune

to another channel 1 MHz higher and listen again for the signal, repeating the process

until no signal is heard. This helps to approximately establish the expected propa-

gating frequency range.

e. If the operator believes he heard a chirp signal, he should retune his monitor

receiver to the frequency where it was best heard and wait to see if the signal is

heard again exactly 5 minutes after the first recorded observation.