SWEEP PROGRAMMER

11-5820-917-13

transmitter) use. The primary function is to translate the 42-70 MHz output of the

synthesizer to a 2-30 MHz output for the transmitter sweep. The 5 MHz input from

the frequency standard is buffered by the down converter circuit and frequency

multiplied to 40 MHz by the harmonic generator and 40 MHz bandpass filter. The

40 MHz is then mixed with an amplified 40-70 MHz signal from the synthesizer. The

output product of the mixer is the 2-30 MHz receiver sweep which is further ampli-

fied and filtered to produce a 0 dBm (one milliwatt) sine wave output. The down

converter also featues a gating circuit which turns off the 2-30 MHz output when it

is not needed. Gating is used for blanking of the TCS-4B transmit sweep at selected

frequencies and to gate off the unused 2-30 MHz output for RCS-4B application.

4-74. SWEEP PROGRAMMER (figure FO-29). The 5035-2003 sweep programmer

circuit 2A1A 3 controls the frequency sweep by digitally programming the synthe-

sweep programmer contains an 8 decade BCD counter that stores the programmed

frequency data of the synthesizer. This is preset with the sweep starting frequen-

cy (low limit) of 2 MHz. When the sweep START command (from the sounder con-

trol logic) is received, a 100 kHz clock from the synthesizer is gated on to the 8

decade counter. The counter increments by one count on every pulse of the 100

kHz clock .

linear increase in the programmed frequency corresponding to a 100 kHz per second

sweep rate. The sweep continues until it reaches 30 MHz when the upper limit

detect circuit interrupts the 100 kHz clock thereby stopping the sweep and re-

setting the 8 decade counter back to the 2 MHz low limit. If a 2-16 MHz sweep is"

selected the sweep programmer operates as described above except the upper limit

detector is set to 16 MHz and the sweep clock is divided by 2 to 50 kHz.

a. The sweep programmer also contains slip circuits and clock gating circuits

which increase or decrease the basic 100 kHz (or 50 kHz) sweep clock by O. 1, 1.0,

or 5.0%. The resulting slight change in sweep rate allows the RCS-4B receiver

sweep to be advanced or retarded relative to the TCS-4B transmit sweep for syn-

chronization purposes. This slip circuitry is not used in TCS-4B applications.

The blanking control circuit drives RF gating circuits in the synthesizer down con-

verter for TCS-4B transmitter RF blanking, but this circuit is not used in RCS-4B

application.

b. The sweep programmer also contains two digital dividers; the 100 kHz

reference generator, and the VCO divide-by-20 counter. The input to the 100

kHz reference generator is the 5 MHz standard, which is digitally divided by 50

to produce 50 nanosecond wide pulses at 100 kHz rate. These pulses drive the

synthesizer phase detector reference input. The VCO divide-by-20 counter takes

the 42-70 MHz synthesizer output and divides it to the 2. 1-3.5 MHz count output

for use by the frequency counter logic that, in turn, drives the LED displays.

4-75. RECEIVER (2A2) (figures 4-12, FO-32, and FO-33). The 4028 receiver con-

sists of two major circuit sections: the receiver front end section and the output

section. The functional circuits of the receiver are diagramed in figure 4-12.

4-76. RECEIVER FRONT END. Antenna selection is accomplished by two relays,

K 1 and K 2, which connects one of three antennas to the receiver (figure FO-32).

Relay K 3 selects either an antenna or the internal calibrator. The calibrator