[Elecraft] External keyer question...

Sun Feb 17 21:59:11 2002

Rich-
Kevin-
Don-

Thanks for your input (and that from any others I may have missed) about my
earlier external keyer question.

Rich is spot-on with his review of the SA-5010 keyer schematic (see below).
Don and Kevin are also quite right about the need for some sort of switching
interface to avoid the application of what I THOUGHT was +/- 20 VDC on the
two keying lines.  I was WRONG about that.  The duhhh...factor set in for me
about an hour after my post when I was staring at the 5010 schematic over a
cup of coffee.

Awhile later I remeasured the two keying line outputs, and neither shows any
DC voltage existing on them during the TUNE mode of the keyer (or while it's
keying a loaded message for that matter).  They each show some DC resistance
when the keyer is keyed; however, I need to remeasure it to be sure what I'm
measuring "syncs" with the schematic before I ask any further questions
about it.

I've now got one of the the 5010 keying line outputs connected to the K2 via
a short length of shielded cable with a tip-sleeve (i.e. mono) 1/8" plug for
the K2 end, and an RCA plug at the other end for the 5010.

A quick test an hour ago (with the K2's INP HAND menu item enabled) still
yielded no keying occurring with the K2; however, I need to do some more
fiddling with the connecting cable I made up to be sure I've got it rigged
correctly.  I'll post further results in a day or two after some more
head-scratching.

BTW, Rich, did you ever try connecting the 5010m keyer to your K2?  Glad to
hear that it performs well with the TenTec Omni D.

73

Steve Banks
K0PQ
K2 S/N 1599

-----Original Message-----
From: [email protected]
[mailto:[email protected]]On Behalf Of Rich Lentz
Sent: Sunday, February 17, 2002 16:15 PM
To: Kevin Cozens; Steve Banks; [email protected]
Subject: RE: [Elecraft] External keyer question...

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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