[Elecraft] KX3 and Data Mode Interface

[Edward R. Cole]

This seems a popular topic on the KX3.

For computer interfacing the KX3 for running various soundcard 
programs a simple interface is needed for PTT, Keying, and transmit 
audio.  It is assumed that one side of the IQ baseband will serve for 
connection of Rx audio to the soundcard.

A couple choices are given for PTT:
1) using the Mic-PTT
2) using GPIO input

Transmit audio from a soundcard will have to be:
1) isolated
2) reduced in amplitude to drive the mic input properly.

RS232 needs to be isolated from KX3 PTT and KEY.

An external unit is what looks practical and will need the proper connectors:
1) Four contact mic connector w/ suitable length cord
2) ACC2 connector (if used)
3) standard 3.5mm phone jack for soundcard interconnect (get that from RS)
4) breakout of serial cable RTS line and DTR line
5) connector for KX3 KEY jack.
6) transistors to isolate RTS and DTR
7) resistive divider (pot) for setting Tx audio level
8) miniature pcb isolation transformer for audio

A simple interface can be made "very tiny" using sm components, 
though may be more than will fit the standard DB9 (9-pin subD) jack 
shell.  I'm giving some thought to manufacture such an item, but I 
need to receive delivery of my KX3 for development.

What would folks like this to look like?  How long should cords be?

73, Ed

-------------------------
Date: Sat, 17 Mar 2012 20:29:41 +0100
From: Frode LA2RL <la2romeolima at gmail.com>
Subject: [Elecraft] KX3 and Data Mode Interface
To: Elecraft at mailman.qth.net
Message-ID:
         <CADpT02T=Qw5TDWuv=Xev=2vr56GOs52MOr8ambxd+twmfrXUWA at mail.gmail.com>
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The K3 Manual says clearly that the Line In and Line Out signals are
isolated with transformers and that these ports therefore can be connected
directly to a computer sound card.

I have read carefully through the KX3 Preliminary Manual but I have not
found any information about isolation of the input and output analog
signals. I therefore suppose that the KX3 does not have any isolation on
these ports, however on page 18 the manual says that you can connect the
computer audio to the MIC jack and the KX3 phone jack to the computer's
audio input. So I am still somewhat confused.

73
Frode LA2RL





73, Ed - KL7UW, WD2XSH/45
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