[GreenKeys] Loop supply options

[Jim Cooper]

On 7 Sep 2019 at 9:56, John, W9DDD wrote:

> There is a Hammond transformer -
> 166G80 which has a 80 VAC secondary.
> That with a bridge rectifier would
> result in about 112 VDC depending on
> your line voltage.  I think it was
> under $30 at Mouser.  That might be
> the cleanest solution. 
> 
> Triad used to make a 1:1
> transformer.  (maybe still do). 
> This would result in more like 140 to
> 160 VDC output so you'd want want
> more like 2,500 ohms instead of 2,000
> for the current limit resistor. 

Keep in mind that you WANT a higher 
DC voltage, as the square waveform you 
want for good 'range' depends on the 
rise time of the square wave ... high V 
and high R make better square waves. 

That's why the original loop supplies were 
not made with 12v filament transformers !!

w2jc