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INSTRUCTION BOOK NO. 7077R
A.W.A. BEAT FREQUENCY OSCILLATOR
TYPE R7077
INSTRUCTIONS FOR ORDERING REPLACEMENT PARTS.
When ordering spares or replacement parts, the type number (and, if shown, the serial number) marked on the component should be quoted. If it does not bear its own type number, or if it is a piece part, the circuit reference number and the type and serial numbers of the unit in which it is mounted should be quoted. The circuit reference number and the type number should be checked against the corresponding ones on the diagram.; it should be noted that the main unit may comprise a number of sections so that only the sectio type number should be quoted.
SECTION A.
SCHEDULE OF EQUIPMENT.
Item 1. One A.W.A. Beat Frequency Oscillator Type R7077
Item 2. Valves required for the operation of item 1:
Three Radiotrons type 6J8G
One Radiotron type 6V6G
One Radiotron type 6U5/6G5
One Radiotron type 6X5G
Item 3 Instruction Book No. 7077R.
NOTE: This is a guide to the items which comprise a normal equipment, but may be varied to suit the requirements of each installation.
SECTION B.
DESCRIPTION.
1. GENERAL DESCRIPTION.
The A.W.A Beat Frequency Oscillator Type R7077 is a compact and portable unit designed for general test purposes. The complete unit is housed in a grey wrinkle finished steel case measuring 12” x 8” x 8” and the total weight is 24 lbs. A leather carrying handle is fixed to the top of the case to improve the ease of portability,
The unit has a frequency range of 30 cycles to 13 kilocycles which is covered in a single step. A 9 inch diameter, semi-circular scale is engraved on the process plate forming the front of the unit and this is calibrated directly in cycles.
Particular attention has been paid in the design to the elimination of frequency drifts caused by variations in temperature and supply voltage. Silvered mica condensers and robust coil formers have been used in the L.C. circuits of the oscil1ators and resistance stabilising is employed.
The unit is completely self-contained and all controls and output terminals are mounted on the front panel.
2 SUMMARY OP CHARACTERISTICS.
(a) Power Supply
Built-in Unit: 200-260 volts)
50-60 cycles ) Input
Power Consumption: 36 watts.
(b) Valves.
Radiotron 6J8G: Fixed oscillator and buffer amplifier (100 Kc/s.)
Radiotron 6J8G: Variable oscillator and buffer amplifier (100-87 Kc/s.)
Radiotron 6J8G: Mixer
Radiotron 6V6G: Output.
Radiotron 6U5/6G5: Zero indication.
Radiotron 6X5G: Rectifier.
Total: 3 x 6J8G
1 x 6V6G
1 x 6U5/6G5
1 x 6X5G
SECTION B. (Contd.)
(c) Frequency Range.
30 cycles to 13 kilocycles.
(d) Frequency Control.
Dual-ratio 3” diameter knob.
(e) Frequency Scale.
Semi-circular, 9” diameter.
(f) Frequency Calibration.
Below 100 cycles the scale is almost linear, above 100 cycles it is approximately logarithmic.
The scale is calibrated every -
5 cycles from 30 to 100 cycles
10 cycles from 100 to 200 cycles
20 cycles from 200 to 500 cycles
50 cycles from 500 to 1,000 cycles
100 cycles from 1 to 2 KC/s.
200 cycles from 2 to 5 KC/s.
500 cycles from 5 to 13 KC/s.
The calibration is correct to within 2% over the entire frequency range.
(g) Output.
250 milliwatts maximum (see (j) ), i.e., 12.5V across a 600 Ω load. Open circuit output up to about 30 volts.
(h) 0utput Impedance.
600 Ω
(j) Harmonic Distortion.
(i) With 2 volts into 600 Ω load:
At 60 cycles, less than 4% (R.M.S. sum)
At 400 cycles, less than 1% (R.M.S. sum)
At 1,000 cycles, less than 1% (R.M.S. sum)
At 7,500 cycles, less than 1% (R.M.S. sum)
(ji) With 10 volts into 600 Ω load:
At 50 cycles, less than 10% (R.M.S. sum)
At 400 cycles, less than 3% (R.M.S. sum)
At 1,000 cycles, less than 3% (R.M.S. sum)
At 7,500 cycles, less than 3% (R.M.S. sum)
(iii) With 10 volts into 50,000 Ω load:
At 7,500 cycles, less than 2% (R.M.S. sum)
(k) Noise Level
Reference level 6 milliwatts.
Better than 40 db.
(m) Frequency Response.
Flat within 2 db from 30 to 10,000 cycles.
(n) Radio Frequency Content:
From fixed oscillator: Negligible
From variable frequency
oscillator: About 0.05 volts into 600Ω
(o) Power Consumption.
36 watts.
(p) Front Panel Controls.
1 - Main Frequency Control, calibrated from 30 to 13,000 cycles.
1 - Zero set control.
1 - voltage output control calibrated 1 to 10 in arbitrary units.
1 - Magic-Eye Zero Beat Indicator.
(q) Mechanical Data.
Width: 12”
Depth: 8"
Height: 8"
Weight: 24 lbs.
SECTION C.
DESCRIPTION OF OPERATION.
1. GENERAL.
The audio output of the unit is obtained by selecting the difference frequency component which is produced by mixing the outputs of two high frequency oscillators. This difference frequency is filtered, amplified and supplied to the output terminals.
Of the two ...
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