[GreenKeys] Power supply for Eric's demodulator

[Jim Haynes]

Since the teleprinter loop is opto-isolated, those who are willing to
live dangerously could just use a halfwave or bridge rectifier on the
120V AC power line (fused, of course) for the loop supply.  You'll need
about a 2.5K 10 watt resistor for the loop current adjustment, since
120V will give about 150V DC.

If you'd like to live less dangerously, I believe you can still get a
120V:12.6VCT transformer from Radio Shack.  Two of these back-to-back
will isolate the 120V from the power line; and you can fullwave rectify
the 12.6V to get about 9VDC to put into the voltage regulator on the
board.

Another possibility is a transformer you can get from Mouser, Triad
Magnetics FD6-12 which is a 12.6V CT transformer with two 120V
primaries.  The intention is to use the two primaries in parallel for
120V line and in series for 240V line.  However the thing seems hefty
enough that you could use just one of the primaries on the 120V line
and use the other as an isolated output to rectify for the loop supply.
And then the 12.6V winding with a full wave rectifier will give you
the low voltage DC to feed the voltage regulator on the board.  I'm
not offering any guarantees, but the power drain on the 12.6V winding
is so low that it should be OK to use one primary for a primary and
the other for a secondary.  Anyone who is more expert on magnetics
is welcome to confirm or deny.

Jim W6JVE