17 Apr
2004
17 Apr
'04
12:23 a.m.
John Honniball wrote:
MTPro(a)aol.com wrote:
John, I don't understand this description of the knife switch:
So, anyone else like to expose any other
collecting
Well, I have the usual (!) collection of old electronic test gear, plus
phones, audio and video gear:
http://www.gifford.co.uk/~coredump/oldsad.htm
>
A porcelain knife switch, used for
disconnecting an aerial from a radio receiver. The two centre terminals of the switch are
connected to the radio and the two left-hand terminals go to the antenna. Finally, the two
terminals on the right are earthed. The switch incorporates two spark-gaps which are
intended to prevent lightning from damaging the radio. But the real protective measure is
to switch the handle over to the earthed position whenever the radio is not in use. This
connects the aerial directly to earth, and disconnects it from the radio.
<<
It seems to me that the radio is connected to earth instead of the aerial...
Bert