Local oscillator

TM 11-6625-3017-14

-12 V line should be not more than +2 mV,

5.4.3 Power supply

and preferably about +1 mV.

Test equipment:- a, b, c and d

5.4.4

Local oscillator

(1)

Measure the output of the -18 V and -12 V

regulated supplies at the points illustrated in

Fig. 5-2..

Test equipment:- e, f, g' and h

(1)

Connect the frequency meter and millivolt-meter via

a T-connector to the output plug of the oscillator,

PLB. Turn the LEVEL control fully clockwise.

(2)

Switch to oscillator RANGE 1-2, tune through the

range and check that the dial calibration is within

3% of the frequency meter reading and that the

level is between 0.5 V and 1 V. If the calibration

accuracy is outside limits, withdraw the local

oscillator unit and reset range trimmer L2 for

optimum accuracy at the low frequency end and/or

C1 at the high frequency end. Replace the local

oscillator unit and recheck the calibration.

(3)

Switch to oscillator RANGE 3-4, tune through the

range and check that the dial calibration is within

+3% of the frequency meter reading and that the

level is between 0.6 V and 0.8 V. If the calibration

accuracy is outside limits withdraw the local

oscillator unit and reset range trimmer LA for

optimum accuracy at the low frequency end and/or

C14 at the high frequency end. Replace the local

oscillator unit and recheck the calibration.

(4)

Switch to oscillator RANGE 3-4 and turn the

CRYSTAL switch to position 1. Insert a 22 MHz

Fig. 5-2. Regulated supply measuring paints

crystal into socket 1 and check that the frequency

meter reads within 22 MHz the crystal tolerance

If the voltages are not within 1% of nominal, adjust

after tuning the Local Oscillator to 22 MHz.

RV1 for -18 V or RV2 for -12 V.

5.4.5

Harmonic generator

The location of these potentiometers is illustrated in Fig.

Test equipment:- i.

4.1.

(1)

Shunt the resistor in series with the I. F. OUT

(2)

Connect the wave analyser to the -18 V line and

socket by a 1 k2 resistor.

check that the 50 Hz, 120 Hz and i80 Hz ripple

components are each less than 100 -V. Check

(2)

Connect the I. F. OUT socket to the R. F. Input of

that the same components on the -12 V line are

the Polyskop and the R. F. IN socket to the R. F.

each less than 50 - V.

Output of the Polyskop.

(3)

Replace the wave analyser with the differential

(3)

Set the Polyskop controls as follows:

voltmeter. Check that the -18 V line voltage does

not change by more than 20 mV when the a. c.

supply is varied from 180 to 260 V, (or 90 to 130 V).

The change on the

5-5