Roger started by reminiscing about his early interest in Amateur Radio while at school. Starting with a crystal set, he built a number of valve receivers and an oscilloscope using a VCR97 ex-military cathode ray tube. His parents never heard about the 2000V DC electric shock he gave himself, where he was unable to let go of the circuit and only saved himself by kicking the mains switch to off. He described the advances in receiver design which have resulted from the development of valves, transistors and integrated circuits: RF amplifiers, super-regenerative detectors, superheterodyne- and single-sideband receivers to the direct conversion receiver, which is now used in many mobile telephones. Then he talked about the generation of stable, low-noise signals at UHF and microwave frequencies – to illustrate harmonic generation, the phase-locked loop and frequency synthesis. After his very comprehensive talk, Roger was thanked by LRS President, John Cooke GM8OTI.
One of Roger’s first receivers was an ex-govt Eddystone 358X.
Roger’s current constructional project is a frequency synthesiser.
Close-up of the oscillator board for the frequency synthesiser.
Testing the oscillator board.
