A reasonable selection of the Hackaday readership will have had their first experiences of computing on an 8-bit machine in a black case, with the word “Sinclair” on it. Even if you haven’t work with one of these machines you probably know that the man behind them was the sometimes colourful inventor Clive (now Sir Clive) Sinclair.
He was the founder of an electronics company that promised big results from its relatively inexpensive electronic products. Radio receivers that could fit in a matchbox, transistorised component stereo systems, miniature televisions, and affordable calculators had all received the Sinclair treatment from the early-1960s onwards. But it was towards the end of the 1970s that one of his companies produced its first microcomputer.
At the end of the 1950s, when the teenage Sinclair was already a prolific producer of electronics and in the early stages of starting his own electronics business, he took the entirely understandable route for a cash-strapped engineer and entrepreneur and began writing for a living. He wrote for electronics and radio magazines, later becoming assistant editor of the trade magazine Instrument Practice, and wrote electronic project books for Bernard’s Radio Manuals, and Bernard Babani Publishing. It is this period of his career that has caught our eye today, not simply for the famous association of the Sinclair name, but for the fascinating window his work gives us into the state of electronics at the time.
Step back to a time when AM was king …
With a little persistence we were able to locate some of the early [Sinclair] work: 1959’s Practical Transistor Receivers Book 1, and 1962’s Modern Transistor Circuits For Beginners. They are both slimline paperback volumes roughly the size of an A4 or US Letter sheet, and contain 36 and 35 different circuits respectively.
Practical Transistor Receivers was one of the first such books on transistor circuitry from this publisher, and was evidently intended to serve as a transistor primer for constructors who had never used the new devices. There is an extensive section on both the range of transistors and of diodes that were on the market in 1958 when it was written. This is an interesting read in itself, containing as it does a look at many long-disappeared names in the industry on both sides of the Atlantic. All the semiconductors are germanium, diodes are point-contact, all but a few transistors are PNP, and though there are no point-contact transistors by this stage in the decade all but a few surface barrier devices use alloy-diffusion construction. Gain and cut-off frequency figures are extremely low by today’s standards, these devices are still very much the earliest examples of their type.
Modern Transistor Circuits For Beginners is pitched more towards people unfamiliar with electronics, and contains a chapter introducing the components of the day. There are the discrete components that will be familiar to readers in 2017, but also a table of colour codes with examples of devices you might not have encountered that use them. You know about resistors with coloured bands, but have you ever seen a tip-body-and-dot resistor?
It is especially interesting that both books deal with exactly the same subject of simple AM radio receivers, despite the title of Modern Transistor Circuits leading the reader to believe otherwise. Electronics was entirely synonymous with radio and audio at the amateur level at the time, and this book follows a trend that is evident from the list of other titles from the same publisher on the back cover.
The circuits start with the very simplest receivers which are not much more than a crystal set with an audio stage added, and move through tuned-radio-frequency designs to regenerative and super-regenerative receivers. Modern Transistor Circuits has a few layout diagrams for good measure, to aid the beginner in identifying transistor leads.
Another feature of these circuits is that they show an obvious heritage from the tube-based circuits that anyone involved in electronics would have been familiar with at the time. Transformers are used as inter-stage coupling where we would now use a capacitor or a level shifting circuit, and power amplifiers are high-impedance single-ended designs. The super-regenerative circuit has a quench oscillator using a sizeable LC tuned circuit, where an RC oscillator of some type would almost certainly be placed in a modern take on the same design.
… and transistors cost an arm and a leg.
Nearly sixty years ago a transistor was an exotic and expensive device. Equivalents for an OC71 audio transistor appear in an advert in the back of Modern Transistor Circuits for 5 shillings and 9 pence, which with a bit of conversion to decimal currency and taking into account the inflation of the intervening years, equates to £6.03, or $8.45 in 2018 terms. Today I can buy a tape of 40 2N3904 silicon transistors with a gain figure in the several hundreds and a cut-off frequency in the high VHF range for that price from a retail supplier, and of course for similar prices I can also benefit from five decades of integrated circuit development. It’s possible then that radio circuits were the main outlet for electronics enthusiasts at the time because they were something that could deliver a reasonable result from a circuit with relatively few components, anything requiring multiple devices would have soon bankrupted anyone wanting to try them.
The [Sinclair] business developed through the decade with radio kits that brought to the fore his love of miniaturisation that would become the signature of products bearing the name. You can see the further development of some of the radios in these books with his rise to public prominence through his long progression of tiny radios designed to fit in a matchbox, a theme to which he returned in the 1990s with an FM radio in an earpiece. In the 1970s came the calculators and the miniature televisions, followed into the 1980s through a separate Sinclair company by the home computers that would eventually be sold to Amstrad. He is infamous for his mid-1980s C5 three-wheeled electric buggy, but he pursued his interest in alternative transport into the 1990s with a succession of folding bicycles of unusual design, and an electric drive add-on for conventional bicycles.
Footnote: though Sir Clive Sinclair is a published author and famous name in the world of home computers, it is fair to say that he is not the Clive Sinclair, author. That honour must go to Clive Sinclair, the prolific British novelist, who sadly died at the start of March 2018.