[Elecraft] K3 Firmware updating

[Edward R Cole]

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" <lists at subich.com>
Subject: Re: [Elecraft] K3 Firmware updating
To: elecraft at mailman.qth.net
Message-ID: <4C18F68A.8090009 at 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
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