This project appears in a nicely-presented article starting on page 332 of the September 1969 edition of Practical Wireless Magazine. I first came across it, perhaps during a wet break, in the school library during my first term at secondary school in that month and year. I recall reading and re-reading the article with fascination - a real working miniature radio that I could build all by myself!
No doubt the inspiration came from commercially-available micro radios of the time, such as this one, claiming to be the world's smallest radio, from Sinclair Radionics. I suspect the makers of these radios wanted to give the impression that they were miniaturized fully-functional radios rather than the minimalist ones in very small packages that they actually were.
To make the most of the two transistors in the mini-two, the designer eschewed reflexing in favour of regeneration (a limited amount, according to the author), using a so-called gimmick capacitor consisting of a pair of insulated wires twisted together. Since this was inside the case, it would have meant taking the cover off in order to optimize reception for each newly-tuned station!
A complete lack of technical know-how on my part didn't stop me from buying the components, including the hairgrips box (the contents of which may be of use to our longer haired friends, as the author put it) for the container, and obtaining a soldering iron from a friend who was also intrigued by the radio. However, the project had a long gestation and I didn't get around to building it until the mid-1970s. Even then, I didn't bother with the case and tuning knob!
As far as I recall, after all those years of anticipation, I was disappointed to discover that I could only pick up one station with it and only that after wandering around the house trying to get a signal, fiddling with the controls as I went. Sadly it was put to one side before being discarded some time later during a clear-out. Perhaps if I'd persevered, I'd have got more out of it. On reflection, it seems pretty impressive that it could receive any station without an external aerial.
Fast-forward to a few years ago and I was curious to compare its performance with some other minimalist radios I've been playing with, notably this one that uses a Darlington Pair transistor so I attempted to re-create it. Getting hold of the specified transistors was no problem. To save time, but deviating from the design, I opted to use the the coil and tuning capacitor in a Maxitronix crystal radio and connected that to a breadboard containing the required components, using the small winding of the coil to take the signal to the circuit. I used two slightly depleted 9 volt batteries for power, giving around the required 15 volts. I dispensed with the gimmick capacitor and instead used a 25 pF trimmer, no longer being interested in the miniature aspect of this radio.
It did pick up BBC Radio 5 Live, possibly Talk Sport, and others at night, but in order to do so, it had to have an aerial connected to the larger coil, no doubt because there are far fewer MW stations around these days, so we can no longer rely upon the presence of powerful nearby transmitters. It was somewhat fiddly to tune, reception was dependent on the position of the aerial and some regeneration was always needed. Volume was acceptable, but there was some background whistling. My perception of it was less favourable than the Darlington Pair radio and the single-transistor-with-reflexing-and-regeneration version of the Ladybird radio. Sadly, my evaluation was cut short when the crystal earpiece I had been using was dropped and rendered unusable!
Overall, I'd say that while the radio has an interesting design, it's really a curio of limited usability. As for being an ideal project for the beginner, regrettably, I have to disagree with the author - as a newbie, after all that hard work, the last thing you want is disappointment! Perhaps the series of articles in PW entitled Simple Receivers for Beginners beginning in June 1968 would have been a better starting point?
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