![]() With this double-doping process, and also the improved rate-grown variant, it was difficult to accurately produce and connect to the very narrow base region required for high frequency performance. The first successful method of making a junction transistor involved creating the base layer by dropping a tiny p-type pellet into the n-type melt while drawing the crystal, and then converting it back to n-type. This transitional set had 37 germanium transistors in sockets connected by conventional point-to-point wiring, just like its valve predecessors. In 1964 National introduced a transistor version of the receiver that retained the classic ‘PW’ gear drive but no longer had plug-in coils. National HRO receivers had been a long-time favourite with radio amateurs, and around 10,000 sets were used by the Y-Station service that supplied intercepted enemy wireless messages to Bletchley Park during WW2. The 830 was Eddystone’s last valve receiver and continued in production until January 1973. In 1971 you could choose between the valved Model 830 receiver and the transistorised 1830 version with slightly better performance. The more compact EC10 that was introduced in 1963 was more successful and over 6,000 were made, followed by around 10,000 of the Mk2 version with an S-meter and fine-tuning control. Its performance was inferior to its parent and it was dropped two years later. Eddystone’s first solid-state communications receiver was the S960 virtually a model S940 with 12 transistors in place of valves. It took several years for many of the traditional shortwave receiver manufacturers to change from valve to transistor designs and not all did so successfully. ![]() Starting with the Model IM-30 in 1961, Heathkit also produced a series of rudimentary transistor testers and curve tracers that evolved with the device technology until the final Model IT-2232 was phased out in 1990. After replacing the audio output stage by a higher power amplifier, I used the compact set as a mobile receiver for several years but its performance didn’t match that of good valve receivers of that period. The 10-transistor kit set used three Mullard germanium AF115s as RF amplifier, local oscillator and mixer, with four OC45s for the BFO and three IF amplifiers coupled by 455kHz piezoelectric ‘transfilters’. One of the first shortwave transistor receivers for radio amateurs to be made in the UK was the Heathkit GC-1U Mohican, which was sold in 1961 for £38 15/- (around £800 in today’s money). His crystal-controlled rig used one 2N113 germanium alloy junction transistor as 7MHz oscillator, driving a second as doubler/output stage with 78mW input. In September of that year W1OGU, a technician with Raytheon, achieved the first transatlantic QSO with a transistor transmitter, working OZ7BO in Copenhagen and G3AAM in Birmingham on 14MHz. One germanium npn transistor acted as oscillator/mixer, with output at 1230kHz for a broadcast receiver, and a second pnp one as Q-multiplier/BFO. In mid-1956 IDEA launched the Regency ATC-1, a simple two-transistor mobile converter that tuned the five HF amateur bands. These were devices that failed to meet the full professional specifications and would otherwise have been scrap. At this time manufacturers such as Philips made ‘experimental transistors’ available to amateurs at low prices. A simple receiver using two GEC point-contact transistors was described in the January 1954 issue of Wireless World, while a topband (160m) transmitter by G3IEE using a Mullard OC50 featured in the RSGB Bulletin for March. In the UK, a miniature 3.5MHz transistor transmitter by G5CV aroused great interest when operated at the 1953 Amateur Radio Exhibition. The February 1953 issue of QST described how RCA manager K2AH even made a 146MHz CW QSO with W2UK over 25 miles with a power input of 24mW to a single selected experimental point-contact germanium T165/6 transistor. ![]() Radio amateurs also started experimenting with transmitters as soon as suitable transistors became available at accessible prices. By 1950 enthusiasts in the UK were building simple receivers using commercially-available Raytheon point-contact transistors that were primarily made for hearing aids. Using little more than a microscope, an Avometer and a pulse source for point-contact forming, enterprising amateurs were soon making their own transistors by replacing the single cat’s whisker of selected germanium diodes by two. ![]() Wireless World first reported the invention of the transistor in October 1948. Dr Bruce Taylor HB9ANY concludes his look at the history of the transistor, relating how the invention impacted amateur radio and moving on to modern developments in integrated circuitry and microprocessors.
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