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Re: [TenTec] relay delay in Tentec QSK amps

To: "Discussion of Ten-Tec Equipment" <tentec@contesting.com>
Subject: Re: [TenTec] relay delay in Tentec QSK amps
From: "Paul Christensen" <w9ac@arrl.net>
Reply-to: Discussion of Ten-Tec Equipment <tentec@contesting.com>
Date: Thu, 6 Dec 2007 07:03:12 -0500
List-post: <mailto:tentec@contesting.com>
> It's also very easy to add diode summing networks to combine the
> keyer with the computer keying line (like the K2 does). I build
> these networks into the output of the keyer (which comes with
> several spare RCA jacks that work nicely for this purpose). One
> caution -- you may need to use Germanium diodes with the Herc II and
> some radios.


I found the same issues many years ago when creating a two common shack 
busses -- one to split the keyer output to feed multiple radios and the 
other as an amp key line buss such that multiple radios key one of two Alpha 
amps.  I resorted to using 1N34 germanium diodes after the keyer output 
until I decided to replace them and use an array of MOSFET switching 
transistors, each capable of switching high-voltage AC/DC loads.

The primary benefit of building out the transistor array is that isolation 
is better than that attained with germanium steering diodes.  As an 
alternative to N4NT's excellent suggestion, another benefit is that it 
easily allows one to key the amp slightly ahead of the rig's key line output 
on rigs where there's a tendency for leading waveform edge hot-switching. 
One output port from the keyer goes to the radio, another keyer port goes to 
the amp in parallel with the rig's key line.

I built my Super CMOS II keyer back in '92 from a QST construction article 
and since it was a home-brew project anyway, I later added a half dozen 
ground-isolated RCA connectors (for switching AC loads, if necessary) just 
for this purpose.  Been working great this way ever since.

Paul, W9AC 

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