[TenTec] Omni QSK with Alpha's 87A QSK

[Paul Christensen]

Jim:

I'm not sure my messages are making it to you through the reflector.
With one simple mod to the Omni Six's Control Board, you can accomplish your
goal.

This is my third post relating to this today, but I'll repeat it again: The
Omni's Q16 can be modified to key your Alpha 87 silently and with ample T/R
time to ensure that hot switching does not occur, but not so much that QSK
performance is compromised.  See my previous post for an explanation on the
steps involved.

To answer your question, the Omni outputs an "open collector" at the TX OUT
terminal.  Simply, put it goes to circuit ground when keying occurs.  The
Omni's TX EN line also wants to see an "open collector" from a mating
Ten-Tec amplifier.  The purpose of this unique circuit is to precisely time
the T/R switching circuit and thus prevent amplifier hot-switching.

Yes, it would be great to use the TX OUT terminal.  Don't.  If TX EN is left
open, the Omni will not key.  One may be tempted to split the output in two
directions.  Don't.  Isolation will be compromised.  The jumper is required
when an amplifier is not in the enable loop and isolation will be
compromised if the jumper is broken for this purpose..

The Good News:

A new TX OUT line is created with the modification I spoke of.  In fact, the
base of Q16, through R29 is connected to TX OUT after the modification.  Q16
then provides the fast, necessary key line to your Alpha 87 and isolation is
maintained.  Don't try to overcomplicate your situation by trying to use the
TX EN line in conjunction with the TX OUT line.  It's not necessary.

If you follow this technique, you will be more than happy with it ANY CW
speed when using your Alpha 87.

-Paul, W9AC

-----Original Message-----
From: Jim Reid <jreid@aloha.net>
To: Ten-Tec, Inc., Amateur Radio Sales <sales@tentec.com>; Ten-Tec Reflector
<Tentec@contesting.com>; JAMES T BRANNIGAN <JTBRANNIGAN@prodigy.net>
Date: Sunday, September 20, 1998 6:16 PM
Subject: Re: [TenTec] Omni QSK with Alpha's 87A QSK


>
>
>>The reason your TT is not plug capatable with the Alpha is the same reason
>>Nikon lenses will not fit a Minolta...it is called MARKETING....
>>and this  is not a bad thing, it is simply good business..
>
>
>Has nothing to do with physical plug type;  probably has to do with
>keying signals.  Both the Alpha and the Omni key on with a key
>closure to ground.  And a "virtual" key closure to ground is what
>the 87A puts out on its' "c" RCA socket to go back to the
>transceiver to signal it is ready to be driven.  All this occurs
>in well less than 20 msec or so.
>
>Would really wish someone would tell me what the Omni puts out
>from the  TX OUT terminal to the KEY IN terminal on the back of
>Ten Tec linears;  and then,  what comes out from the KEY OUT
>terminal of  their linears to be fed back into the TX EN terminal
>of the Omni's.  From what follows,  you will see why I believe
>it is exactly what the 87A wants to see;  that is sink to gnd on
>transmit.
>
>To quote the Ten Tec manual once again, "...the Logic board
>generates a transmit acknowledge voltage at connector 63.
>This signal [whatever it might be?] becomes the external
>keying loop that is normally jumpered on the rear panel.
>If an external [QSK capable] amplifier is to be used,  it
>can be included within the keying loop so that the amplifier
>can control the  [QSK] timing of the keying and prevent hot
>switching."
>
>So,  as  the 87A requires a closure to gnd.  from such a
>keying loop, and provides the same back to the loop,
>i.e. a sink to ground,  isn't that exactly what the Ten Tec
>loop is doing when Q11 conducts on the Omni Control
>Board,  Fig. 4-18,  pg. 4-17 of the VI+ manual??  Or,
>perhaps it is the exact opposite in the Omni:  lifted
>from gnd.   as the transmit signal within the keying
>loop.  No way to know which way it is from the schematic,
>at least I don't see it.  But in reading the above  quoted
>text,  it would seem that Q11 conducts when the key
>acknowledge signal is present,  thus providing the
>"virtual" key closure to gnd.
>
>Anyway,  I am still not getting this set up to operate QSK.
>
>73,   Jim,  KH7M
>same back to
>
>
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>
>


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