I encountered an interesting situation building a new control panel
box for my station that controls all the radio equipment: antenna
relays, preamps, transverters, amplifiers and switches between two
radios: FT-847 and the K3/10. I used opto-isolators to separate the
radio side from the computer. Specifically using the RTS and DTR
lines of RS-232 to control PTT and keying functions used by a lot of
ham sw. I was surprised to discover that the RS-232 levels caused
the opto-isolators to activate on both LO and HI levels. Apparently,
they did not like the -11vdc LO logic level. I bypassed the
opto-isolator direct to 2N2222 relay drivers with no issues.
What this has to do with the current thread is I have two computers
that I like to use with the radios (one computer runs old DOS-based
programs) so I route the RS-232 lines thru a four-port parallel
switch that has sub-D25 pin connectors. I was concerned that serial
would not be passed but on inspecting the switch the connectors are
connected pin-for-pin so it is transparent to whatever is
connected. I use standard serial cables with sub-D25 to sub-D9.
One more comment: I had to add some wiring to support RXD and TXD in
another HB A-B switch so that downloads would pass to the K3. The HB
switch is wired with twisted pair stripped from cat-5e cable.
73, Ed - KL7UW
haven't uploaded either the new firmware or editor (soon)
------------------------------------------------------
Message: 1
Date: Wed, 16 Jun 2010 12:06:34 -0400
From: "Joe Subich, W4TV" <li...@subich.com>
Subject: Re: [Elecraft] K3 Firmware updating
To: elecraft@mailman.qth.net
Message-ID: <4c18f68a.8090...@subich.com>
Content-Type: text/plain; charset=ISO-8859-1; format=flowed
> Or do you mean the RS232 control lines? If so, and the device
> gets powered down, doesn't it's hold on the control lines go
> away???
No, with no power applied to RS-232 devices - whether it be a
computer serial port, MK2R+, MKII, or the K3 the "unpowered"
lines will load the other lines so they will not work properly.
Without special circuits, it is not possible to connect two
drivers to a single RS-232 port at the same time.
The best solution is the two port RS-232 switch.
Note, updating with K3 is a special case since the K3 does not
require the use of handshake signals for updating. Other rigs
require handshake between their update software and the rig.
Since application controlled handshake is not supported AT ALL
by any microHAM interface, any upload capability is out of the
question for other rigs.
73,
... Joe Subich, W4TV
microHAM America, LLC.
http://www.microHAM-USA.com
http://groups.yahoo.com/group/microHAM
73, Ed - KL7UW, WD2XSH/45
======================================
BP40IQ 500 KHz - 10-GHz www.kl7uw.com
EME: 144-600w, 432-100w, 1296-60w, 3400-fall 2010
DUBUS Magazine USA Rep dubus...@hotmail.com
======================================
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