[AMPS] [Fwd: TS450/850 & SB-200 Keying]

[Joseph J. Duerbusch]

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Date: Fri, 14 Aug 1998 12:34:18 -0500
From: Joseph Duerbusch <jduerbusch@mdc.com>
To: duerbusc@mvp.net
Subject: TS450/850 & SB-200 Keying

High speed switching is the best way to
go, either with a high speed relay or
the QSK-5.  But for the short term, low
cost solution, I found several other
idea's.

1.  QST had a very good article in
Hinks and Kinks, 
1991 January   QST                     
               p. 37
                            More on
Interfacing Solid-State Transceivers 
                            and the
SB-200 Amplifier: A Power-MOSFET 
                            Source
(Jaeger)

This is a external interface with no
modifications to the radio or amp.

2.  The soft-keying by Harbach
electronics.  I put this in my SB-200
and cured the "Hot Switching" problem.
At least I can't see the swr jump when
I first keyup.  

3.  On my TS-850S, and should be the
same on the TS-450S, pin 7 on the
remote jack has +12 volts on transmit. 
Looking at the diagram, this comes off
the same line that keys the internal
relay.  It looks like this would be a
good place to drive a High
voltage/Current transistor to drive the
relay in the amp.  In fact, if you look
at Richards webpage, under "Circuit
Improvements for the TS-440S" he has a
circuit that does just that.  The
circuit is for a SB-220 for positive
keying so you would need a different
circuit for the negative keying of the
SB-200 but it should work the same.
http://www.vcnet.com/measures/

Also, I just wanted to thank all that
replied to my earlier request for help
with the L-4B Power Supply.  I took
everyone's advise and rebuilt it
myself, and it worked!  Thanks again.

Joe K0BX



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