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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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