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Old 24th Nov 2022, 6:38 pm   #21
HamishBoxer's Avatar
Join Date: Aug 2007
Location: W.Butterwick, near Doncaster UK.
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Default Re: 100 years of BBC

The "Knife Switch" looked like a knife blade and was ceramic base and used to earth aerials in thunderstorms etc.

Of course some were indeed used to switch power, a bit lethal depending on voltage across it!
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Old 24th Nov 2022, 6:51 pm   #22
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Location: Wiltshire, UK.
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Default Re: 100 years of BBC

Yes, the usual Knife-switch was a ceramic- or Bakelite-based beastie, looking like a miniature version of what you might see in Dr. Frankenstein's Laboratory.

"More Power, Igor!! More Power!!"

There were 2 kinds - one a simple 1-way version, you wired the antenna to one side and the other side to earth, so when the switch was closed they were shorted together and any static charges picked up by the antenna were drained away to earth.

The other kind was a 2-way switch; you connected the antenna to the centre, then one of the outer terminals went to the radio, the other to earth.

You had to remember to throw the switch.... not much good if you usually had it in 'radio' mode and the thunderstorm arrived while you were out at work!

Attached photo shows the second type.
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Old 24th Nov 2022, 9:57 pm   #23
Radio Wrangler
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Default Re: 100 years of BBC

note the asymmetric clearance distances of the switch in the photo above.

Radio goes to the left, Earth to the right. antenna to the centre.

Can't afford the volcanic island yet, but the plans for my monorail and the goons' uniforms are done
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