[GreenKeys] LTSpice

[Jeffrey D Angus]

On 7/21/2013 11:26 AM, Chris Elmquist wrote:
> This is a great discussion guys.   Is there a reason (other than
> not being authentic or period correct) that you wouldn't use a TVS diode
> for this problem today?
>
> Chris N0JCF
There are a few "TTY loop to digital" converter circuits out on "the web".
One of them uses a pair of back to back 200 v Zener diodes to clamp the
kick back spike.

My issue would be the non-linear response and how it would affect the
mechanical switching times of the selector magnet.

The real purpose of the snubber circuit is to protect the keying circuit.

BSS, "before solid state" the weak link was the switching contacts for
the loop keying. Unprotected they would arc which in turn would make
them wear out faster. Or, God forbid, weld themselves together.

ASS, "After solid state" (note my horrible pun) the problem was excessive
voltage or reverse voltage doing awful things to the keying circuit.

Nothing is perfect, all designs are a trade off and compromise between
several issues until a point it reached of what works and works reliably.

Jeff-1.0
wa6fwi