Radio frequency oscillator 1A14A1

TM 11-5820-695-35

frequency synthesizer 1A14 front panel.

The

(1) Radio frequency oscillator 1A14A1

thumbwheel switches can be set between 4400.0 MHz

utilizes a voltage controlled oscillator (vco) to produce

and 5000.0 MHz to provide a divisor from 9080 to

an rf output signal in the 284.3750 MHz to 303.1250

15080. When the thumbwheel switches are set between

MHz frequency range. The specific frequency of the rf

4400.0 MHz and 4699.9 MHz, the intermediate output

output signal is determined by the vco bias signal. Two

signal from electronic frequency converter 1A14A2 is

rf output signal levels (high and low), at the same

divided by between 9080 and 15078, respectively. Each

frequency, are provided by radio frequency oscillator

0.1 MHz step in the switch changes the divisor by two;

1A14Al. The 20 milliwatt (nominal) rf output (high)

e.g., switch setting 4400 establishes division by 9080

signal is applied through electrical frequency synthesizer

and switch setting 4400.1 establishes division, by 9082.

1A14 main chassis (synth output) to the transmitter

When switches are set between 4700.0 MHz and 4999.9

frequency multiplier circuits. A detected rf output signal

MHz, the division is again between 9080 and 16078,

level (meter), derived from the rf output (high) signal is

respectively. When the switches are set to 5000 MHz,

applied through the main chassis (synth level) to the

the divisor is set at 15080. Variable 1 frequency divider

meter panel assembly 1A15A8 meter selector switch.

1A14A4 divides the if output frequency from 1A14A2 in

The 1 milliwatt (nominal) rf output (low) signal is applied

accordance with the 1 MHz and 0.1 MHz thumbwheel

to electronic frequency converter 1A14A2 (part of

switch settings. Variable 2 frequency divider 1Al4AA5

phase-lock loop circuits). The vco bias voltage input to

divides the count output from variable 1 frequency

1A14A1 is derived from a comparison of the rf output

divider 1A14A4 in accordance with the 1000 MHz, 100

(low) signal from 1A14A1 with a reference signal. A

MHz, and 10 MHz switch settings.

The variable

lamp test signal from the main chassis TEST switch is

frequency dividers divide the if output signal from

applied to test the failure lamp in 1A14A1. The failure

1A14A2 to produce the divide-by-N (N) signal. When

lamp lights when the rf output signal is not present.

phase-lock is established (rf output from 1A14A1 is

(2) Electronic frequency converter 1A14A2

exactly at the frequency indicated by the thumbwheel

converts the rf output (low) signal from 1A14Al to an

settings), the frequency of the divide-by-N pulses is

intermediate frequency (if) output signal that is

exactly 1.5625 kHz. If the thumbwheel switch settings

compatible with the digital integrated circuits in variable

are changed to a new frequency, the countdown ion the

1 and 2 frequency dividers, 1A14A4 and 1A14A5. This

variable frequency divider circuits changes causing the

is accomplished by first dividing the rf output (low)

frequency of the divide by-N pulses to change. For this

signal (284.375 MHz to 303.125 MHz) by two and then

condition (phase loop unlocked), the frequency of the

mixing the resulting frequency (142.1875 MHz to

divide-by-N pulses is not exactly 1.5625 kHz. The

151.5625 MHz) with a 128 MHz reference frequency.

divide-by N output pulses from variable 2 frequency

The 128 MHz reference signal is produced in 1A14A2 by

divider 1A!4A5 are applied to fixed frequency divider

multiplying the 8 MHz signal from standard radio

1A14A6 and audio frequency phase error detector

frequency oscillator 1A14A7 by 16. The intermediate

1A14A3.

frequency 14.1875 MHz to 23.5625 MHz) is produced by

(4) Fixed frequency divider 1A14A6 produces

mixer circuits within 1A14A2 and is applied to variable 1

a 1.5625 kHz reference signal from the 8 MHz input

frequency divider 1A14A4.

signal from standard radio frequency oscillator 1A14A7

(3) Variable 1 frequency divider 1A14A4

and compares the 1.5625 kHz reference signal with the

operates in conjunction with variable 2 frequency divider

divide-by-N pulses received from 1A14A5. A two-bit

1A14A5 to divide the if output signal from 1A14A2.

correction signal and a phase lock signal are generated

Variable 1 frequency divider 1A14A4 has the capability

within 1A14A6 as a result of this comparison. The two-

of dividing the if output signal by 200. The divided if

bit correction signal is used in determining the vco bias

output signal (count) from 1A14A4 is applied to variable

voltage which is produced by audio frequency phase

2 frequency divider 1A14A5. Variable 2 frequency

error detector 1A14A3. The phase lock signal is applied

divider 1A14A5 has the capability of dividing the input

(synth alarm) to alarm monitor 1A5 circuits and is used

signal by 80. Thus, the variable frequency dividers

to control an alarm indicator on meter panel assembly

have the capability of dividing the if output signal from

lA15A8. If the 1.5625 kHz reference signal and the

1A14A2 by 16,000 (200 x 80). However, the maximum

divide-by-N pulses are in phase, the two-bit

division capability is not utilized. The division ratio is

established by the thumbwheel switches on the electrical

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