[Boatanchors] TCS Tx & Rx

[Sandy]

I had been using my old TCS-12 for YEARS modified this way and I didn't 
notice any difference in the "droput time" of the relay.  MY CW speed 
usually runs 20-25 WPM sent with a "bug" and it's made no difference at all 
in the relay action.  Sure did kill the spike on the keyline though!

Instead of speculating about it, just try it.

73,

Sandy W5TVW

-----Original Message----- 
From: Mike Hanz
Sent: Sunday, March 25, 2012 5:20 PM
To: boatanchors at mailman.qth.net
Subject: Re: [Boatanchors] TCS Tx & Rx

A single diode, regardless of whether you are protecting the key
contacts directly or hanging it on the offending coil, does in fact
affect the dropout time of the relay significantly.  Back when I was a
young engineer, I designed relay testing equipment for high reliability
weapons, and that fact was drilled into me big time.  There is a good
rundown on the various methods of suppressing the spike from the
collapsing magnetic field at
http://www.pickercomponents.com/Pages/Application%20Notes/Coil_Supression_vs_Relay_Life.pdf


Included on the second page is a chart of dropout time increase versus
suppression technique that is more than illuminating.  A diode in series
with a zener of approximately double that of the coil operating voltage
is what we used in our circuit designs - the reason should be clear.
Obviously you have to choose the zener rating carefully to manage the
strength of the collapsing magnetic field, which varies with the size of
the relay.

73,
Mike

> >  I'm no CW op but I'd expect the diode would lengthen the relay release
> >  time, maybe quite a lot.
>
>
> Some passive parts across the key might have a noticeable effect like
> that but the backward diode doesn't have any timing effect. If there is
> one it would take lab equipment (atomic clock?) to measure it. At morse
> code keying rates any stretching that might be there is 'virually'
> nonexistent. And..it *DOES* get rid of that spike induced when the
> magnetic field from the relay coil collapses. It's highly recommended in
> solid state circuits to preserve keying transistors that are used to
> energize relays.

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