Alignment Procedures; Introduction; 100 Kc/S I.f. Amplifier; 100 Kc/S (L-C) Filter - Racal Instruments RA-117 User Manual

14. Alignment Procedures

14.1. Introduction

11. The receiver will, under normal conditions, maintain the factory alignment over an ex-
tremely long period of time. Consequently ALL POSSIBILITY OF OTHER CAUSES
OF TROUBLE SHOULD BE ELIMINATED BEFORE RE-ALIGNMENT IS CON-
SIDERED.
12. If it becomes necessary to re-align any part of the receiver, only a very small angular
adjustment of any trimmer should be necessary. The signal generator must have a
high degree of frequency resetting accuracy and be very stable.
13. Unless otherwise stated, the front panel mounted meter is used as the output indicator.
14.2. 100 kc/s I.F. Amplifier
FIRST AND SECOND I.F. AMPLIFIER
14. Remove the second v.f.o. valve V12. Set the SYSTEM switch to MAN, the R.F./I.F.
GAIN to MAX and the meter switch to R.F. LEVEL. Connect the signal generator
(100 kc/s c.w) via a 0.1 F capacitor to the grid of V16 (pin 1) Adjust C191 to obtain
maximum indication on the meter. The output from the generator required to produce
100 A deflection on the meter should be approximately 320mV. Connect the signal
generator via a 0.1 F capacitor to the grid of V14 (pin 1) and connect a 4 7-kilohms
damping resistor across L72. Adjust C179 and C195B to give maximum indication.
15. Remove the 4 7-kilohms resistor from L72 and connect it across L73. Adjust C171 for
maximum indication. Remove the 4 7 kilohms resistor. The signal generator output
required to produce a 100 A deflection should be approximately 800 V. Tune the
signal generator through the passband and note the 'double peak' response. The peak
separation should be approximately 9 kc/s and be symmetrical about 100 kc/s. If the
peak amplitudes differ, slight re-adjustment of C195B will compensate for this. The
6dB bandwidth should be approximately 14 kc/s.

14.3. 100 kc/s (L-C) Filter

16. Remove the left hand gusset plate. Remove the 1 7 Mc/s crystal XL300 and set the
controls as in 14 above. Connect the output signal generator (100 kc/s) to socket
SKT303. Remove the L-C filter can. Locatethe two red free-ended leads connected at
one end of the trimming capacitors C153 and C158 in the second and third sections
of the filter and connect the free ends to their respective 470k damping resistor R77
and R80 at the terminal post ends. Replace the filter can. Set the bandwidth to 100
kc/s. Tune the signal generator to give maximum indication on the front panel meter
then switch to 1 2 kc/s. The frequency of this setting should be within
100 kc/s. Adjust the trimming capacitors C162, C158, C153 and C147 in this order
several times until maximum output is obtained.
17. Remove the L-C filter can and disconnect the red leads from the terminal post ends of
the 470-kilohms resistors. Replace the filter can. Set the controls of the signal generator
[37]
100 c/s of