Frequency Change

11-5820-919-40-1

2-53. Audio Input/Output Connectors.

2-48. Frequency Change. The frequency

change (

) signal is generated each

The audio connectors J1 and J2 enable

the operator to connect a handset or

time a new operating frequency is

headset and microphone combination to

selected. The AF signal is momentary

the radio set. A CW telegrapher's key

0 (grid) during each change in setting

of the frequency select switches S1

can be substituted for the microphone

for code operation.

thru S5. AF is not generated by S6.

The AF signal indicates to the

modulator/demodulator that a new

2-54. Handset or Headset and Microphone

Operation. When a handset or headset

frequency has been selected.

and microphone are used in conjunction

2-49. Volume off/max (left half of

with the radio set, they are connected

figure). The VOLUME OFF/MAX S9 is a

to the control panel by audio input/

conventional on/off switch and poten-

output connectors J1 and J2. The push-

tiometer. The switch, when closed,

to-talk (PTT) signal and the Xmt Audio

applies +28v On power from the bat-

are routed through the low-pass L-C

tery pack to the MODE, SB, and LIGHT

filter networks contained in the audio

switches on the control panel, and to

filter to the modulator/demodulator.

all radio set circuits. The potenti-

The audio filter rejects any rf which is

ometer R1 controls the level of Rcv

picked up by the cables leading to the

Audio developed by the modulator

radio set from the microphone or hand-

demodulator by tapping off a portion

set. The PTT is used by the modulator/

of the audio (from the VOLUME control)

demodulator to key the modulator for

back to the modulator/demodulator.

transmit operation. Rcv Audio from the

modulator/demodulator is also routed

2-50. Mode. The MODE (mode select)

through the audio filter to the handset

switch S8 provides both a +28v Xmt

or headset.

Enable and/or a Data Enable signal to

the modulator/demodulator. The Xmt

2-55. CW Key. A cw telegrapher's key

Enable signal (V-TR and D-TR) permits

is normally used in conjunction with a

Xmt RF to be generated by the modulator/

headset, but can be used with a handset.

demodulator when the modulator is keyed.

The cw telegrapher's key outputs a CW

The Data Enable signal (DTR) indicates

Key signal which is filtered and routed

to the modulator/demodulator that a

to the modulator/demodulator. The CW

data transmission has been selected.

Key signal is used by the modulator/

The modulator/demodulator will cause

demodulator to activate the keyline

the receiver agc time constant to be

circuits and internal 1-kHz modulation

shortened. When a voice receive (V-RCV)

tone circuits.

or data receive (D-RCV) has been

selected, the +28v Xmt Enable signal

2-56.

SYNTHESIZER MODULE (Figure 2-5).

is inhibited, preventing transmission

(receive operation only).

2-57. General. The synthesizer pro-

vides input to the modulator/demodulator

2-51. Sideband Select. The SB (side-

in the form of three high frequency LO

band select) switch S7 applies either

signals and one audible tone. The high

an upper (USB-open) or lower (LSB +28v)

frequency LO signals are 5 MHz, 70/80

Sideband Select signal to the synthe-

MHz, and 77-105 MHz. The 70-MHz LO

sizer. The signal is used to switch the

signal is outputted if USB is selected

70/80 MHz LO to provide either upper or

and the 80 MHz is outputted if LSB is

lower single sideband operation.

selected. The frequency of the 77-105

MHz LO signal is 75 MHz above the fre-

2-52. L i g h t The LIGHT switch S10 is a

quency selected at the control panel.

press-and-hold switch which applies +28v

The audible tone (1 kHz) is used in the

On to panel lights DS1 thru DS6. When

modulator/demodulator for alarm signals,

the LIGHT switch is released, the panel

timing functions, and CW Key operation.

lights extinguish.

2-19