c1070_users_manual 电路图.pdf

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1、 MODULATED OSCILLATOR C1070 RadioFans.CN 收音机爱 好者资料库 RadioFans.CN 收音机爱 好者资料库 8 A.W.A. Modulated Oscillator Type C1070 THE PURPOSE OF THE INSTRUMENT. This instrument has been designed for use in servicing all kinds of radio receivers. Modulated or unmodulated signals of any frequency between 100 Kiloc

2、ycles and 20 Megacycles are available. THE FOLLOWING TESTS MAY BE CARRIED OUT RAPIDLY AND WITH AMPLE SERVICE ACCURACY: 1. Alignment of I.F. and R.F. circuits at any desired frequency. 2. Adjustment of receivers provided with wavelength or kilo-cycle scales to correct dial calibration by setting trim

3、mers and padding condenser. 3. Examination of ganged T.R.F. circuits for errors in tracking 4. Measurement of overall sensitivity of all types of receivers at any frequency, and gain of I.F. amplifiers. 5. Estimation of noise level at higher sensitivities by comparison of audio outputs between modul

4、ated and unmodulated carrier of equal strength. 6. Determination of stage gain in I.F. or R.F. amplifiers. 7. Testing of valves for performance under working conditions by insertion of several in succession in a given socket in a receiver and noting the change in stage gain or overall sensitivity. 8

5、. Checking the performance of A.V.C. in receivers. 9. Measurement of selectivity of I.F. or R.F. amplifiers in terms of band width in kilocycles, for input signals one hundred or one thousand times larger than the signal on tune required to give some chosen value of audio output. 10. Determination o

6、f image ratio, or the ratio of the micro-volts input at the image or second spot frequency at the micro-volts at the wanted signal frequency, both giving equal audio output. This compressive list of tests covers more than is usually required in receiver servicing. None of these tests requires an ins

7、trument with capabilities of accuracy available in a signal RadioFans.CN 收音机爱 好者资料库 1 generator. Consequently the controls and methods of calibration can he modified in the direction of speeding up and generally simplifying operation. This object has been the aim in the design of the Type C1070 modu

8、lated oscillator, and has been achieved with but small reduction in accuracy below average signal generator performance. Design and Performance FREQUENCY RANGE. 100 K.C. to 20,C00 K.C. in six ranges, selected by a switch. Range A, 96 K.C. to 250 K.C. Range B, 240 K.C. to 600 K.C. Range C, 560 K.C. t

9、o 1420 K.C. Range D, 90 metres to 220 metres (1,360 K.C. to 3,330K.C.). Range E, 37 metres to 96 metres (3,120 K.C. to 8,100 K.C.) Range F, 15 metres to 38 metres (7,900 K.C. to 20,000 K.C.) All ranges are directly calibrated on a rotovisor type dial: A, B and C are marked in kilocycles and D, E and

10、 F in metres. Calibration accuracy is better than 1per cent on range C. and within 2 per cent on the other ranges. OUTPUT. The attenuator calibration indicates directly the approximate microvolts output on Ranges B and C. It is calibrated 1, 3, 10, 30, etc., up to 100 M (100,000) with two extra mark

11、ings not carrying accompanying figures. The one adjacent to the 100,000 Mark is 300,000 and the Inst one is the extreme position for the pointer when turned clockwise. The approximate output signal on the other ranges may be estimated from the following table Range Multiplying factor for Attenuator

12、Calibration Range Multiplying factor for Attenuator Calibration A 1.4 B 1 C 1 D 0.5 E 0.2 F 0.08 2 CONTROLS The oscillator has four controls (from left to right): No. 1. Range Switch. This control selects the coil for use on any desired range. No. 2. Battery Switch. The battery switch has three posi

13、tions. (i) The first position, OFF; both the A Battery and B Battery circuits are open. (ii) In the second position, MOD. OFF, the A Battery is connected to both valves but the B Battery is connected to the R.F. oscillator only. (iii) In the third position, MOD. ON, the B Battery is connected to the

14、 Modulator valve also; thus modulated and on modulated carrier are available. No. 3. Frequency Selector. By turning this knob any desired frequency throughout the range corresponding to the setting of the range switch may he obtained. Use the scale corresponding to the setting of the Range Switch. N

15、o. 4. Attenuator. By turning this knob the amount of the output signal may be adjusted to any desired level. The approximate value of this signal may be estimated from the data given on page 3. OPERATION. 1. Set the modulated oscillator about one foot to the left of the receiver under test. 2 Connec

16、t the output cable to the terminals of the oscillator. Connect the braided lead with coloured tracer in the braiding to the insulated terminal of the oscillator by means of the spade terminal. Connect the plain lead to the earthed terminal. 3. Connect the other end of the cable to the receiver under

17、 test. The plain lead is to be connected to the earth terminal and the other lead (tracer) to the aerial terminal or grid cap of a valve as required. When connected to the grid cap it is necessary to connect a resistor between the grid cap and earth to complete the bins circuit (about 250,000 ohms o

18、r larger is suitable). 4 Connect an Output meter in the plate circuit of the last valve. See Fig. 2. 5 Turn the battery switch to the MOD. ON position and select the desired test frequency by means of the range switch and the frequency control. 6. Tune the receiver to the frequency of the oscillator

19、 and adjust the attenuator to give a convenient deflection on the meter. Any tests listed on page I may now be carried out. CAUTION.-Be sure that the Battery Switch is turned OFF when the oscillator is not in use. 7 6 the average maximum R.F. output on each hand is therefore: A . 400 Millivolts B .

20、300 “ C . 300 “ P . 150 “ E . 60 “ F . 25 “ The attenuator reacts noticeably upon the carrier only at the higher outputs. The frequency change caused through advancing the attenuator control from low outputs up to the position marked l00M is approximately as follows: High frequency end of hand 0.3 p

21、er cent. Middle of band 0.1 per cent. Low frequency end of band 0.05 per cent. On position 300 M the shift of carrier frequency will be three times greater, as the change of frequency is directly proportional to the indication of the attenuator control. It is important that the special shielded cabl

22、e supplied should be used with the oscillator always, otherwise the above figures for R.F. output on each hand will not hold. This cable has the correct characteristics to suit the attenuator, and to behave as a dummy aerial on the broadcast ranges (for alignment purposes only). Leakage signal throu

23、gh the attenuator cannot be detected except at about 20 M.C. where it is of the order of less than one microvolt. The relative ratios of attenuation as marked on the attenuator scale are almost unaffected by the value of the operating radio frequency. MODULATION. The modulator oscillator is adjusted

24、 to approximately 400 C.P.S. by adjusting the air gap of the TAl060 Transformer. The modulation depth is set at about 30 per cent. on the low frequency bands by means of a resistance in parallel with the tank circuit of the audio oscillator. The only serious departure frown the figure of 30 per cent

25、. for the modulation depth occurs on band F where it rises to about 45 per cent. The battery switch has 3 positions, OFF, MOD. OFF, and MOD. ON, allowing the radio frequency output to be obtained free from modulation in the middle position. CONSTRUCTION. The coils and wave change switch together wit

26、h the wiring and the oscillator valve socket are individually screened, and form together a complete assembly. This assembly, the variable condenser and modulator oscillator system are mounted to a rear panel. In this way radio frequency currents in this panel cannot give rise to external stray fiel

27、ds due to the shielding effect of the front panel and outside metal case. 3 The variable condenser is operated by a smooth eight to one reduction drive situated between the two panels. The piston of variable capacitance attenuator also lies between the two panels and is of special design. It contain

28、s no fragile electrical parts, as in the resistance type attenuators, that may require replacement. At one end of the brass tube is placed an insulated metal disc that is connected to the tank circuit of the R.F. Oscillator. A second and similar disc is carried on the face of an insulated piston, an

29、d is connected to the output terminal on the front panel. The batteries are strapped in the rear of the case, and are wired to a terminal panel at the side where clearance holes (insulated) are provided for insertion of the prods of a voltmeter to check voltages without opening the case. EQUIPMENT.

30、Valves. Two type 30 Radiotrons are used - one as R.F. oscillator and one as 400 cycle Audio oscillator. Batteries. Four 4.5 Volt Bias Batteries (drain 60 M.A.) and one 60Volt Light Duty Battery (drain 3 to 5 M.A.) are required, The Bias Batteries are connected in parallel to operate the filaments in

31、 series. The condition of the batteries may be checked with a voltmeter through the holes in the side of the case. Satisfactory Voltage Limits are as follows: A flattery 3.5 to 4,5 Volts. B Battery 50 to 60 Volts. It is not desirable to continue to use batteries of voltages below these limits. To in

32、stal or change batteries or valves proceed as follows: 1. Turn the tuning control (the knob second frown the right) so that pointer indicates 100 K.C. on range A, otherwise the tuning condenser may be damaged. 2. Lay the oscillator on the bench face up, and take out the screws round the edge of the

33、front panel. 3 Lift the oscillator out of the case by taking hold of the edge of the front panel. 4. See that a good 30 valve is held firmly in each socket. 5. Assemble the batteries in the back of the case. See that they are held firmly with the straps provided. See diagram Fig. I. 6. See that the

34、battery switch is turned to OFF 7. Connect the batteries according to the diagram Fig. I 8. Reassemble the oscillator in the ease. 4 UTPUT METER. To make satisfactory use of the modulated oscillator it is necessary to connect an output meter to the receiver under test. A standard rectifier type of o

35、utput meter is most convenient, or a conventional design of valve voltmeter may be used. An economical substitute is suggested as follows: A standard D.C. voltmeter of 1000 ohms per volt may be used in conjunction with a valve operating as a diode rectifier. The valve may have a filament type or ind

36、irectly heated type. The plate and all grids are connected together to form a diode plate. An output meter may be constructed according to fig. 2. Using a D.C. voltmeter of ranges 0- 3. 0-30 and 0-300 volts and resistance 1000 ohms per volt the following A.C. voltage ranges were obtained using a type 76 and a type 30 valve: D.C. Range. R.M.S. A.C. Ranges 30 76 0-300 0-250 0-290V. 0-30 0-33 0-35V. 0-3 0-6.5 0-9.0V 5