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4. Set Selectivity Switch for the required
operating conditions — See Selectivity
Curves
Figure 12.
5. Set Noise Limiter AVC Switch for the
required operating conditions.
6. Set R-F Gain Control fully clockwise.
7. Set Audio Gain Control about halfway.
8. Tune in the station.
9. Reset Audio Gain Control to give desired
volume.
10. Reset Selectivity and Sensitivity (R-F
Gain) Controls and Noise Limiter Control
in accordance with requirements due to in-
terference, station transmission, and other
conditions.
11. Set Tone Control for preferred tone.
12. On CW (A-1) operation set Power-Trans-
mit-Receive Switch to "Rec. CW" (position
4) and set BFO Control to give desired
pitch. When a strong CW signal is being
received, it is necessary to retard the R.F.
Gain Control to reduce the volume.
13. If the receiver is subject to vibration, the
tuning may be locked by turning clockwise
the knurled screw directly beneath the tun-
ing knob. Turning the screw moderately
tight will lock the tuning.
5.13 Diversity Reception: — Provision is made to
operate two or three of these receivers together
for "diversity" reception. For this type of recep-
tion the A.V.C. circuits of the receivers are tied
together. The receivers are operated on separate
antennas, and the receiver receiving the strongest
signal, thus generating the greatest A.V.C. volt-
age, dominates the other receivers. If the separ-
ate antennas are faced to .the incoming signal
at different angles, the good reception with mini-
mum fading results.
Refer to Figure 3: Connect together the ter-
minals, marked "Diversity" of the receivers, and
equip each receiver with a separate antenna.
Tune each receiver to the same station as ex-
plained in Section 5.12 above.
6. MAINTENANCE
6.1 This receiver should maintain its correct fac-
tory adjustments over a reasonably long period
of time. Causes of trouble and the probable
sequency of their development arc outlined in
the following paragraphs:
6.2 Valves:--A noticeable decrease in the sensitivity
of the receiver usually indicates worn out valves.
If the sensitivity is low, remove and check the
valves in a reliable valve tester or substitute new
valves one at a time. See Schematic Diagram,
Figure 11. Valve socket voltages are given in
Table II.
TABLE No. II
VALVE SOCKET VOLTAGES
Valve
Symbol
Type 6SG7
Plate
Volt.
Screen
Volt.
Cathode
Volt.
1st R-F Amplifier
1
235
150
0
Type 6SG7
2nd R-F Amplifier 2
2
35
150
0
Type 6J5
Oscillator
3
110
0
Type 6SA7
1st Detector
4
235
50
Type 6SG7
1st I-F Amplifier
5
235
150
7
Type 6SG7
2nd I-F Amplifier
6
235
150
1.3
Type 6SG7
3rd I-F Amplifier
7
235
150
3.1
Plate Screen Cathode
Valve
Symbol Volt. Volt.
Volt.
Type 6H6
2nd Det. & AVC. 8
Type 6H6
Noise Limiter
9
Type 6SJ7
1st Audio Amplifier 10
83
34
0
Type 6V6GT/G
Power output
11
256
240
0
Type 6J5
B.F.O.
12
40
0
Type VR-150
Voltage Regulator 13
150
0
Type 5Y3GT/G
Rectifier
14
300
NOTE These voltages all measured to chassis. Measured with a 1000 ohm per volt meter. Variations
of
±
20% may be expected due to resistance tolerances, etc.
[91
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