[ICOM] Warning about W1GEE interface cables

[Dave Bernstein]

I use the KB7SG-style interface with my 781 and 756, driving the CI-V
bus with a 2N3904. You wouldn't think its Vol would be any better than a
vanilla open-collector TTL gate. Most CI-V interfaces just drive the
CI-V bus with the TTL side of a MAX-232 (which isn't open collector, but
that's another story); its not known for an exceptionally low Vol
either, is it?

Still a mystery...

    73,

        Dave, AA6YQ

-----Original Message-----
From: icom-bounces at mailman.qth.net [mailto:icom-bounces at mailman.qth.net]
On Behalf Of Doug Faunt N6TQS +1-510-655-8604
Sent: Tuesday, June 01, 2004 22:05
To: icom at mailman.qth.net
Cc: icom at mailman.qth.net
Subject: Re: [ICOM] Warning about W1GEE interface cables


   From: "Dave Bernstein" <aa6yq at ambersoft.com>
   Date: Tue, 1 Jun 2004 21:29:18 -0400

   Since the transceiver side of the interface is a simple TTL
   open-collector bus, it is indeed challenging to guess what the W1GEE
   circuit must be doing to reliably fail with two specific transceiver
   models. Anyone have a W1GEE schematic?

If the two radios require that the "low" voltage to be slightly lower
then the other ICOM radios, and the W1GEE I/F doesn't quite pull that
low, that could be the reason.

I was building some interfaces, and found that some radios required that
the pull-down be a little closer to ground then standard opto-isolators
would provide.  I found some NEC components that are called "solid state
relays" but could also be described as opto-isolators with FET outputs,
that did the trick.  The PTT circuit in the IC706MKIIG data interface
(as opposed to the ACC connector) had the problem, to bring it back to
ICOM rigs.  Look in the Mouser catalog. 

I think people have had this problem with FSK keying on the FT1000's,
also.

73, doug


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