Electronic Frequency Converter IA14A2 Block Diagram Description

TM 11-5820-695-35

frequency divider 1A14A4. The amplified 14.1875 MHz

by meter detector diode CR3 to produce a dc current

if output signal is also applied to bias diode CR6 on

proportional to the rf signal level. The meter current

board A1 which rectifies the signal to provide a turn-off

(detected rf level) is 25 microamperes when the rf

bias voltage for lamp driver Q8. With lamp driver Q8

output (high) signal level is 20 milliwatts. The detected

turned off, the failure lamp DS1 is extinguished (normal

rf level is applied through main chassis low pass filter

condition). When the if output signal is not present or

1A14RL4 and applied to synthesizer position of meter

drops to a low level, the turn-off bias is reduced and

panel assembly 1A15A8 meter selector switch as a

lamp driver Q8 turns on causing the failure lamp DS1 to

synth level signal used to monitor output of electrical

light red (alarm condition). The failure lamp DS1 is

frequency synthesizer 1A14.

tested by pressing the TEST button on the electrical

frequency synthesizer 1A14 front panel. Pressing the

(2) Board A2. The rf output signal (between

TEST button applies 5 vdc to lamp driver Q8 producing

284.3750 MHz and 303.1250 MHz) from vco

a bias which over rides the turn-off bias and causes

subassembly Y1 is amplified by digital amplifier Q1 and

failure lamp DS1 to light. Voltage regulator diode CR,5

Q2 to a 1 milliwatt output level. The amplified rf output

on board A1 produces 6.2 vdc which is applied to rf

(low) signal, is applied to electronic frequency converter

amplifier (Q4 and Q5), the divide-by-two circuit Q1

1A14A2. The amplified output signal from the digital

through Q3 and lamp driver circuit Q8.

amplifier Q1 and Q2 is detected by lamp detector diode

CR1 and applied to diode CR2 on board AS. The

Variable Frequency Dividers 1A14A4 and

detected signal is then applied to lamp driver Q3 on

1A14A5 Block Diagram Description (fig. 5-13).

board A3. When the rf output level from the digital

amplifier is 1 milliwatt (normal condition), the detected

signal biases the lamp driver Q3 off causing the failure

(1) General. The variable frequency divider

lamp DS1 to be extinguished. When the rf output level

modules divide the if output frequency from 1A14A2 in

from the digital amplifier Q1 and Q2 drops below 1

accordance with the thumbwheel switch settings (4400.0

milliwatt (alarm condition), the lamp driver Q3 is biased

MHz to 5000.0 MHz) to produce the divide-by-N output

on causing the failure lamp to light red. The lamp is

pulses.

As stated previously, the variable divider

tested by pressing the TEST button on the electrical

circuits have the capability of dividing the if output

frequency synthesizer 1A14 front panel.

frequency by 16,000, but the divisor is limited to a

number from 9080 to 15080 by the thumbwheel switch

Electronic Frequency Converter IA14A2

settings ((2) below). The thumbwheel switches provide

Block Diagram Description (fig. 5-13). The electronic

ground connections to the switch gate inputs of the

variable frequency divider modules in accordance with

frequency converter 1A14A2 consists of two printed

their settings (para 2-56a).

circuit boards A1 and A2 that translate the rf output (low)

The ground connections preset the number in the

signal from radio frequency oscillator 1A14A1 to an

associated registers. The 1000 MHz and 10 MHz

intermediate frequency which is applied to variable 1

thumbwheel switches preset the divide-by-eight ripple

frequency divider 1A14A4. The rf output (low) signal is

through counter registers in 1A14A5 with a number from

between 284.3750 MHz and is applied to a divide-by-

4 to 7. The 10 MHz thumbwheel switch presets the 10

two circuit consisting of Q1, Q2 and Q3 on board A1.

MHz divide-by-ten registers in 1A14A5 with a number

The divided signal (142.1875 MHz to 151.15625 MHz) is

from 0 to 9. The 1 MHz thumbwheel switch presets the

amplified by rf amplifiers Q4 and Q5 and applied to the

1 MHz divide-by-ten registers in 1A14A4 with a number

local oscillator input port of mixer Z1. The 8 MHz signal

from 0 to 9. The 0.1 MHz thumbwheel switch presets

from standard radio frequency oscillator 1A114A7 is

the 0.1 MHz divide-by-ten registers in 1A14A4 with a

applied to board A2 where it is multiplied by 16 through

number from 0 to 9. Variable 1 frequency divider

multiplier stages Q1, Q2, and Q3 producing a 128 MHz

1A14A4 also contains a circuit which divides the if

output signal. The resultant 128 MHz signal is applied

output frequency by two before it is applied to the 0.1

through emitter follower Q4 to the signal input port of

MHz divide-by-ten registers. The registers in both

mixer Z1 on board A1. The mixer Z1 output is the

modules count down the divided-by-two if output

difference frequency (14.1875 MHz to 23.5625 MHz) of

frequency until the count in the registers reaches unique

the two input signals to the mixer Z1. The 14.1875 MHz

numbers

to 23.5625 MHz if output signal is amplified through

video amplifiers Q6 and Q7 and applied to variable 1

2-36