Radio Test Set (p/OIA16) Block Diagram Description

TM 11-5820-695-35

When testing, aligning, or troubleshooting

POWER indicator lights green (normal indication). If the

rf monitor signal is below the predetermined level, the

the R-1467/GRC-144, two 100 MHz signals are applied

RF POWER indicator lights red (alarm indication) and

to crystal mixer diodes 1A16ZICR1, and 1A16Z1CR2.

the summary alarm circuit is enabled.

The 100 MHz signals are generated when the 100 MHz

rf oscillator's ON-OFF switch is placed in the ON

(5) The reflected rf power monitor signal is a

position. With the switch in the ON position, the

detected dc voltage supplied by directional coupler

indicator on 1A2 is lighted, the RADIO TEST SET

1DC1. The dc signal is applied to operational amplifier

indicator on meter panel assembly 1A15A8 is lighted red

(integrated circuit) AR2 through a variable attenuator

and supply voltage is applied to the oscillator circuit.

circuit. An output from the attenuator circuit is also

The LEV ADJ control is used to adjust the oscillator's

applied to the meter selector switch on meter panel

output level. The output level is monitored by setting

assembly 1A15A8. The output of AR2 is applied to

the meter switch to the OSC LEV position. The meter

Schmitt trigger Q8, Q9. The operation of Schmitt trigger

face is marked to indicate the proper oscillator output

Q8, Q9 is similar to that previously described for the

level. The crystal mixer diode currents (CR1 or CR2)

other monitor circuits except the alarm and normal

can also be monitored by setting the meter switch to the

outputs are revised. The outputs of Schmitt trigger QS,

appropriate position.

Q9 are reversed because it is the presence rather than

the absence of a dc voltage at the Schmitt trigger input

Crystal mixer 1A16Z1 receives a sample

that results in an alarm condition.

of the rf output signal from directional coupler 1DO1.

The signal is in the 4.6 to 4.9 GHz frequency range at a

(6) The summary alarm circuit is comprised

level approximately 21 db down from the rf output. This

of the diode OR gate CR12-CR15 and transistor Q23.

signal is mixed with the 100 MHz output signal from 1A2

Each of the normal outputs is connected to the OR gate.

producing frequencies 100 MHz above and below the

For normal operation, transistor Q23 is off

4.5 to 4.9 GHz input. The signal level output of the

(nonconducting). When any one of the alarm conditions

crystal mixer is approximately -32 dbm (9 db below each

occur, the OR gate switches Q23 on (conducting state)

100 MHz input level to the crystal mixer). Variable

causing a transmitter summary alarm condition.

attenuator 1A16AT1 provides two attenuation levels (0

and 30 db). With the OUTPUT LEVEL control set to the

2-15.

Radio Test Set (p/OIA16) Block Diagram

HIGH position, variable attenuator 1A16AT1 provides 0

db attenuation. With the OUTPUT LEVEL control set to

Description (fig. 24)

the LOW position, variable attenuator 1A16AT1

provides 30 db ,(1 db) attenuation. The receive

The radio test set provides a test output signal from

threshold level is approximately -91 dbm. The -91 dbm

Transmitter, Radio T-1054/GRC144 which is applied to

test input level to Receiver, Radio R-1467/G.RC-144 is

Receiver, Radio R-1467/GRC-144. The test output

obtained as follows: (1) The output of crystal mixer

signal is obtained by mixing a sample of the rf output

1A16Z1 is approximately 42 dbm (level was set by

from directional coupler 1DC1 in the T-1054/GRC-144

adjusting the LEVEL ADJ control on 1A2).

with the output from 100 MHz radio frequency oscillator

1A2. The resulting test output signal is separated by

(2) Variable attenuator 1A16AT1 provides 30

100 MHz from the rf output signal is used to align, test,

db attenuation when the OUTPUT LEVEL control is set

or troubleshoot Radio Set AN/GRC-144. The radio test

to the LOW position. Thus, the output of 1A16AT1 is -

set is comprised of 100 MHz radio frequency oscillator

62 dbm.

1A2, crystal mixer 1A16Z1, variable attenuator 1A1AT1,

and the radio test set panel (part of plate assembly

(3) Coupler,

Directional

CU-1890/GRC

1A16). The OUTPUT LEVEL control for the variable

provides a fixed decoupling loss of 20 db. A variable

attenuator, a meter switch, and a meter are provided on

attenuator in the CU-1890/GRC provides an additional

the radio test set panel. The meter switch permits

loss of 0 to ,20 db. The variable attenuator is calibrated

monitoring of the 100 MHz radio frequency oscillator's

at the direct support level to provide the remaining loss

output level and the crystal mixer diode currents of

required for a -91 dbm input to the R-1467/GRC-144.

mixer diodes 1A16ZICR1 and 1A16Z1CR2.

The variable attenuator in the CU-1890/GRC

compensates for inequalities in the rf cabling and

2-42