[GreenKeys] Constant Current Loop

[Sheldon Daitch]

John,

Northern Radio made a loop current regulator module, solid state,
way back in the 1960s.  I first ran across them in the Army, in
TTY loops in comm sites and later found 'em in our VOA TTY setup
in Greenville. 

IIRC, it has one or two low level transistors, a current regulator
pass transistor, and a handful of resistors and maybe even a
zener. 

Very simple to reconstruct, if I can find a copy of the schematic.

73
Sheldon
WA4MZZ

WB6BLV wrote:

>For a long time I have experimented once in a while with constant current
>loops for my TTY equipment.  Long ago Irv Hoff gave a presentation at WA6YKY
>(Northrop Institute of Technology, Inglewood, Ca) that included information
>of holding the current constant in a loop as various combinations of
>machines were patched in and out.  Back then we used a 6V6 with a 1K
>wirewound in the cathode as a means of making the current pretty much
>independent of the number of selector magnets in the loop.  I have been
>using a solid state desing on and off for several decades.  If you have any
>interest in a copy of the schematic, including nominal component values for
>20 and 60 mil loops (GIF or JPG format), please contact me off-list.
>
>73
>
>John
>WB6BLV at inreach.com
>
>
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