View single post by sparks
 Posted: Dec 7th, 2013 09:17 PM
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Joined: Jan 15th, 2008
Location: New Zealand
Posts: 77
Hi Slider, yes, British telecom. I worked in airport comms systems in the 70's, and there were racks of these used for audio network switching. Very reliable. I measured the 5k coil at 19 Henries inductance. Taking a wild stab at the self capacitance, I estimate the coil's self resonance would be about 2kHz, so with the germanium detector, would make it a very sensitive receiver at VLF frequencies - IF we were assuming that conventional reception is how this operates, which is unlikely.
Thanks for the datasheet. I havent seen one of these since those old days. 
Heres a photo of the coil. This one has 2 windings.

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