This the third version of radio-computer interface that I have built. I rebuilt it over
Christmas 2005 to eliminate intermittent problems in the original. It is built on a
Radio Shack project board and installed in a small aluminum box.
Computer interface is by two DB9 connectors that are connected to the computer
soundcard and serial port via a home made switch box (to be described later). The
switchbox provides an "A-B" switching of both audio and RS232 wiring between
two computers and also restores audio to the esternal computer speakers.
Note that the radio-computer I/F isolates receiver and microphone audio by use of
two AF transformers. Control signals from the computer RS-232 serial port control
the sequencer and provide CW keying. S1 switches modes between computer
generated CW and digital modes, such as PSK-31 or WSJT/JT-65. Transistor Q1
provides some isolation between the computer and radio circuits but a better
approach would be using a photo transistor for complete dc isolation. Here is the
diagram for an interface that uses an opto-isolator and the Tx-Inhibit line in the
FT-847.
Connectors J3 and J4 are 4-pin microphone jacks. J4 provides audio and PTT to
the DATA jack on the FT-847. The CW key is connected to the FT-847 CW jack
by the sequencer to ensure proper sequence of switching between receive and
transmit. Sequencer relay jacks C1 and C2 are logically tied to the TX2 port and
change state at the last step going into transmit mode.
Here is the wiring diagram. Photos will be added (soon).
Eventially it is my intent to combine the sequencer, control box, and computer I/F into one
Control box with capability of operating two radios and two computers.
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