If you are thinking that the current amateur licence assessments are more than a little difficult, spare a thought for those that have undertaken the test prior to the current multi-choice answer system. In the 1960s and 1970s there were only two levels of qualification - Unlimited and Limited. The only difference between the two of them was that there was no requirement for Morse Code testing for Limited applicants. Unlike modern times, there was an international requirement for users of the HF bands to have Morse Code qualifications. The Limited licence only permitted operation from 50MHz (6m) and higher frequencies. Theory examination papers generally had 9 questions, some of which had multiple parts. Only 7 questions were to be attempted, credit was not given for more than 7 answers and all questions carried equal marks.
The examinations themselves were essay type, no formulae provided and no answers from which to make a choice. The allotted time for completion was two and a half hours.
February, 1969 - The following questions are from the Amateur Operators Certificate of Proficiency Theory examination of February 1969.
1.
(a) Draw a circuit diagram showing component values of a transmitter using a crystal oscillator on 3530 kc/s (kHz), a triode doubler stage and a beam tetrode power amplifier operating on 7060 kc/s (kHz). Power supply connections only need be shown.
(b) Is it necessary to neutralise the intermediate stage? Give reasons for your answer.
2.
(a) Why is it that an "image" signal can be received on a superheterodyne but not on a tuned-radio-frequency (T.R.F) rceiver?
(b) Explain the precations which may be taken in the design of a superheterodyne receiver to prevent interference from an "image" signal.
3.
(a) Describe with the aid of a sketch the operation of a transmitting aerial suitable for use at an amateur station.
(b) In regard to (a) nominate a particular frequency of operation and give particulars of aerial length.
(c) Would this transmitting aerial also be suitable for reception? Explain.
4.
(a) With the aid of a suitable sketch, describe the construction and principle of operation of a moving coil (dynamic) microphone.
(b) Compare a moving coil and a carbon microphone with regard to fidelity and sensitivity.
5.
(a) Aided by a circuit diagram describe the operation of a full-wave H.T. power supply which uses silicon rectifiers.
(b) Discuss any precautions you would observe when using silicon rectifiers, particularly when operated in series.
6.
(a) With the aid of a block diagram explain the function of each stage of a single-sideband suppressed-carrier type receiver.
(b) Explain how a conventional double-sideband communication receiver could be modified or adapted to enable reception of single-sideband signals.
7.
(a) What are the advantages of transistors when compared with thermionic valves?.
(b) Discuss the precautions which should be observed when working with transistors?.
(c) What advantage does a Field-Effect-Transistor possess?.
8.
(a) Define: (i) parasitic oscillation, (ii) self-oscillation, (iii) harmonic.
(b) Indicate a possible cause of self-oscillation in the final radio-frequency stage of a transmitter.
9.
Calculate:
(i) The peak value of a sine wave which has an R.M.S value of 10 volts.
(ii) The wavelength of a signal whose frequency is 15 Mc/s (15 MHz).
(iii) The current flowing through a 40,000 ohm resistor which will cause a power dissipation of 5 watts.
February, 1971 - The following questions are from the Amateur Operators Certificate of Proficiency Theory examination of February 1971.
1.
In relation to the final Class C radio-frequency power amplifier stage of a transmitter:
(i) Explain why the anode current varies as the tank circuit is brought into resonance; and
(ii) State whether the anode current will vary when a resonant aerial is couple to the tank circuit. Explain.
2.
(a) Define the terms: (i) Parasitic oscillation, (ii) harmonic radiation, (iii) self-oscillation.
(b) Indicate a possible cause of parasitic oscillation in a transmitter and describe how you would locate and suppress such a condition.
3.
(a) With the aid of sketches describe the construction and theory of operation of a helically-wound whip type aerial, fir use in a fixed location, on the 160m band.
(b) What method would you employ to resonate the aerial at the correct frequency?
4.
In relation to a communications receiver define the following terms:
(i) Cross modulation.
(ii) Automatic Gain Control.
(iii) Image ratio.
(iv) Selectivity.
(v) Signal to noise ration.
5.
(a) Explain the construction and operation of a moving-coil (dynamic microphone. Illustrate your answer with a sketch.
(b) Show by diagram how a moving-coil microphone may be connected to the input of an amplifier circuit.
6.
(a) Discuss one method of generating a single-sideband suppressed-carrier transmission.
(b) Compare any advantages and disadvantages of this type of transmission with that of normal amplitude-modulated transmissions.
7.
Explain, with the aid of a circuit diagram, the operation of the detector and audio stages of a transistor type of superheterodyne receiver. Indicate the point at which the automatic-gain-control (A.G.C) potential is obtained.
8.
(a) Assisted by a circuit diagram describe a variable-frequency-oscillator (V.F.O) suitable for use in the 3.5MHz band.
(b) Discuss the factors on which the stability of the generated frequency depend in a V.F.O.
9.
(a) Explain the theory of operation of grid leak bias when used in the final stage of a transmitter.
(b) If the required bias is 60 volts of which 45 volts is applied by an external source, what grid current is necessary to provide this extra voltage if the grid resistor is 3,000 ohms.
August 1972 - The following questions are from the Amateur Operators Certificate of Proficiency Theory examination of February 1972.
1.
(a) Draw circuit diagram of an amateur station transmitter suitable for operation in the 144-148MHz band. Explain briefly the theory of operation of each stage of the transmitter.
(b) Describe how you would tune the transmitter described in (a).
2.
Assisted by a circuit diagram, explain the operation of a cascode radio-frequency amplifier suitable for use in a V.H.F receiver
3.
(a) Describe with the aid of a sketch, the operation of a type of microphone suitable for use at an amateur station.
(b) Draw a circuit diagram of a solid-state type pre-amplifier suitable for use with a high impedance type microphone
4.
Discuss the limitations of a heterodyne type frequency meter when used alone for measuring frequencies in amateur bands 144MHz and above. What additional apparatus would you use to ensure that the measured frequency does in fact, lie in the desired band? Briefly discuss the theory of operation of this additional piece of apparatus.
5.
(a) What is parasitic oscillation and how is it produced?
(b) Why are parasitics undesirable in a transmitter.
(c) Explain the methods you would adopt to locate and suppress them.
6.
(a) Explain the possible causes of interference to television receivers from amateur station transceivers.
(b) Discuss the technical precautions you would adopt to avoid interference from a transmitter to television and broadcast receivers.
7.
(a) Discuss the factors which affect the D.C. resistance of a conductor.
(b) Explain why the radio-frequency resistance of a conductor may differ from its D.C. resistance.
(c) Describe a method of winding which will minimise inductive effects in a wire-wound resistor.
8.
(a) Discuss the features you consider an antenna, operating in the 14MHz anmateur band, should possess to enable it to communicate effectively over very long distances.
(b) With the aid of a sketch, describe briefly, an antenna possessing the features you have outlined in (a).
9.
(a) Find the total capacity when three capacitors of 2, 4 and 5 microfarads respectively are connected:
(i) In parallel, and
(ii) In series.
(b) Calculate the capacitive reactance of the series combinationin (a) when connected across a 50 Hertz supply.
Created 2011 by
Kevin Crockett. Comments and suggestions may be e-mailed to
