[Elecraft] External keyer question...

Sun Feb 17 18:18:00 2002

The Heathkit Manual from the SA-5010 uMatic Memory Keyer states:
" Transmitter and External Keyer Connections

 Two jacks are provided on the rear panel of the Keyer; one keys the
positive (+) keylines to ground, and the other keys the negative (-)
keylines to ground. If you are not sure which jack to use for a particular
transmitter, you may examine the transmitter schematic, or you may simply
try one jack or the other. If you select the wrong jack, the protective
diode across the jack inside the Keyer will continuously key the
transmitter. NOTE: Use coaxial cable between the Keyer and transmitter.  "

My review of the schematic indicates that the center of the + jack goes to
the collector of a NPN transistor, and the center of the - jack goes to the
collector of a PNP transistor, with no source of voltage other than the
voltage on the base of the switching transistor when keyed either +5 or - 3
MAX (at the base of the switching transistor.)  Each jack also has a .001 Mf
cap, for RF protection, and a Diode across the jack to minimize the chance
of destroying the switching transistor in the keyer.  Any voltage on the
collector of the switching transistor would come from the keyed circuit.

Have used it with a TenTec Omni D (all transistor - no tubes) for more than
20 years with no harm to either.

Rich
KE0ZX

-----Original Message-----
From: [email protected]
[mailto:[email protected]]On Behalf Of Kevin Cozens
Sent: Sunday, February 17, 2002 4:20 PM
To: Steve Banks; [email protected]
Subject: Re: [Elecraft] External keyer question...

At 09:39 AM 02/17/2002 -0700, Steve Banks wrote:
>Has anyone on the reflector ever connected a Heathkit SA-5010 Micromatic
>Keyer to his/her K2?
>
>(My recollection from bench-testing the keyer a couple of weeks ago
>was that both lines provide about +20 or -20 VDC when the keyer is keyed,
>but I don't recall for sure

If the keyer has lines with +20 and -20 I would think it was designed to
key old tube based rigs. You can't connect either line directly to the K2
without damaging the K2.

Your best bet is to use the +20V line and build an interface between the
Heathkit and the K2. You want an output from this interface circuit to be
designed such that when +20V comes out of the Heathkit to activate the
transmitter, this results in a transistor conducting to bring the keying
lines to ground.

I think its probably a good job for an optoisolator. After all, you don't
want to take a chance of the +20 getting in to your K2.

Cheers!

Kevin.  (http://www.interlog.com/~kcozens/)

Owner of Elecraft K2 #2172        |"What are we going to do today, Borg?"
E-mail:kcozens at interlog dot com|"Same thing we always do, Pinkutus:
Packet:ve3syb@ve3yra.#con.on.ca.na|  Try to assimilate the world!"
#include <disclaimer/favourite>   |              -Pinkutus & the Borg

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