7 Jan 2017

Early lightbeam tests

Waverley Rd, Kingsbridge, Devon, UK
My interest in light-beam communication goes right back to the 1960s when an old school friend and I used a torch bulb as the TX and an OC71 transistor with the black paint scraped off as the RX detector.

One of our first tests was across the street shown in this photo. I lived in the first house on the RHS and we received the test in the house with bay windows on the left. DX was about 25m! We AM modulated the torch bulb biasing it at half rail if memory serves me correctly. It had a very low frequency response as the torch bulb had a poor HF response, as I recall.

We moved to this house in 1959 but the photo is years and years earlier.

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