Racal RA-117 Radio Receiver - QSL.net
Racal RA-117 Radio Receiver - QSL.net
Racal RA-117 Radio Receiver - QSL.net
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Alignment Procedures 44<br />
stop. Check that the mechanical stops operate before the capacitor end-stops become<br />
effective at both ends of the band.<br />
34. To re-adjust the first v.f.o. calibration, a heterodyne wavemeter should be employed.<br />
This is Coupled very loosely to V7 by placing its input lead in the vicinity of the valve<br />
base. The 1 Mc/s crystal, V12 and V27 should be removed.<br />
35. Set the wavemeter to 40.5 Mc/s and the MEGACYCLES dial to zero. Adjust L36 for<br />
zero-beat. Change the wavemeter setting to 69.5 Mc/s and the MEGACYCLES dial<br />
to 29. Adjust C77 for zero-beat. Repeat adjustment as necessary. Check the frequency<br />
calibration at 1 Mc/s intervals and ensure that the megacycle positions are reasonably<br />
central on the scale markings. Remove the first mixer valve V7 and connect the valve<br />
voltmeter, shunted 12pF, between TP2 and the chassis. Check that the valve voltmeter<br />
indicates at least 1.5V over the range. Refit the 1 Mc/s crystal, V12 and V27.<br />
Antenna Circuit<br />
36. Remove the first V.F.O. valve V5 and the first mixer valve V7 and set the receiver<br />
controls as follows:-<br />
R.F. ATTENUATOR<br />
R.F. <strong>RA</strong>NGE MC/S<br />
SYSTEM switch<br />
R.F./I.F. GAIN<br />
MIN.<br />
1 – 2 Mc/s<br />
MAN.<br />
MAX.<br />
37. Remove the screening cover from around C18A/B and connect a 1 kilohm resistor<br />
across the secondary section (C18B rear section). Set the R.F. TUNE control approximately<br />
7/8ths of its travel in a clockwise direction.<br />
38. Connect the valve voltmeter, shunted to 12pF, between TP2 and chassis. Connect<br />
the output of the signal generator to the aerial input socket. Set the generator for a<br />
frequency of 1 Mc/s.<br />
39. Remove the top core From the transformer L8 and adjust the primary core for a<br />
maximum deflection on the valve voltmeter. (The position of this core should be such<br />
that it tunes at a point nearest the bottom of the transformer).<br />
40. Remove the 1 kilohm resistor from the secondary section and connect it across the<br />
primary section of C18.<br />
41. Refit top core (secondary) and adjust it for a maximum deflection on the valve voltmeter.<br />
42. Remove the 1 kilohm resistor from the primary of C18.<br />
43. Reset the signal generator frequency to 2 Mc/s and adjust the R.F. TUNE control<br />
(C18) for maximum output on the valve voltmeter then adjust the trimmer capacitor<br />
C233 for a maximum deflection on the valve voltmeter also check for symmetrical<br />
response.<br />
44. Repeat the above procedure for the R.F. <strong>RA</strong>NGE switch settings and frequencies listed<br />
in Table 1 below. Check that the maximum voltage input to give 0.5 volts output is<br />
as shown in Table 2 below.