[GreenKeys] Power supply for Eric's demodulator

[Lee Mushel]

Gentlemen,

As I am almost the age that can be called "OT" and have found, much to my 
dismay, that most don't listen to my suggestions I hesitate to suggest 
anything that might be considered reasonable (you have no idea how much 
abuse I have taken on the subject of software defined radio) but why not 
consider what we did 40 or 50 years ago and simply use a Triad N-48X 
transformer?   I have one sitting next to me and I know that starting in 
1959 I used them in all TUs I built.   All you need is the rectifier and 
current adjusting resistor.  I don't think I used a filter capacitor.  Looks 
like Mouser and Allied still sell them.

73

Lee  K9WRU
----- Original Message ----- 
From: "Jim Haynes" <jhhaynes at earthlink.net>
To: <greenkeys at mailman.qth.net>
Sent: Monday, January 03, 2011 9:05 PM
Subject: [GreenKeys] Power supply for Eric's demodulator


>
> 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
>
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