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I purchased this tiny device when I was in my mid-teens, around 1968, for about 50p (or 10 shillings in old money). It came from a small radio shop, adjacent to Worcester Cathedral, that used to sell all kinds of surplus components. The handwritten label on the side of the unit is enscribed '58Mc'. There is no evidence of crystal control, a ferrite slug instead being used to provide fine tuning adjustment. After bringing it home, on applying battery power I recall to my surprise that the unit appeared to be in perfect working order. The transmission could be picked up on the sound channel of a standard 405 line domestic television when set to one of the Band I channels (now all this was not strictly legal, I know, but as a care-free teenager that's typical of the sort of thing we used to get up to!). I remember being impressed by just how good the sound quality was. I stand to be corrected, but my guess is that the device is a BBC studio radio-mic transmitter which would probably have been designed and constructed within their own specialist construction department. There are certainly no manufacturer or serial markings to suggest otherwise. From the components used in its construction, I would hazard a guess that the unit dates from the mid-1950s. I find it quite amazing just how much valve technology they managed to pack inside such a small unit, which weighs no more than about 5oz! However, there is still the question of carrying the batteries to power it - by comparison to the unit itself these must have weighed like a brick! It's difficult to identify all of the valve types employed as some are hard-wired and partially obscured by spring clip mounts. However, those that aren't hard-wired can be identified as type DF66. |