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I was pleased to be informed by Jack Grove¡¯s article ¡°Tinkering helps to dial in the joy of learning¡± (Campus close-up, 23 July) that Saeed Reza Taghizadeh at London Metropolitan University is convinced that, for children, building your own radio is ¡°still a fantastic thing to do¡±. In my boyhood I certainly tried to construct a crystal set but was dismayed to be told that the essential ¡°cat¡¯s whisker¡± did not require a real cat. Moving on to proper wirelesses involved trips to London¡¯s Lisle Street, where shops sold off war surplus stuff for keen radio hams. I only managed to build a set that glowed and emitted a constant low-pitched noise known technically as ¡°mains hum¡±. Nevertheless, visits to Lisle Street in Soho proved to be highly educational.

R.?E. Rawles
Honorary research fellow in psychology
University College London