[GreenKeys] LTSpice

[Jeffrey D Angus]

On 7/21/2013 9:50 AM, Ralph Mowery wrote:
> In it was a mention of the snubbing circuit and that it would contribute
> to the marking bias.
>
> I just wonder that while adjusting the values to solve one problem if 
> maybe
> another problem might be created ?
>
> I don't know enough about computer simulations to say if it is 
> possiable to
> look at how much distortion may be caused by differant values of the
> snubbing circuit or if is even enough to worry about. 
In a word, yes. Having the simulator running is a great exercise in 
"what does
this have an effect on?"

Mostly the snubber affects what happens on the transition from Mark to
Space. And quite frankly, unless you've put an enormous value of C in the
snubber, the Selector magnet is going to pretty much going to let go when
the loop opens up.

However, with too small a value, the over shoot and ringing issues are going
to beat the hell out of the loop keying circuit.

What does make a difference, is the open circuit voltage. Dropping the loop
supply from 120 to 60 volts, and adjusting the current limiting resistor 
back
to 60 mA, really slows down the rise time on the selector magnet current.

Jeff-1.0
wa6fwi