FT-817 Serial Interface

Even though the FT-817 is designed for portable operations, having the ability to connect it to the main station computer has many uses.  CAT and memory management are perhaps the two main uses for such a connection.

The FT-817 can easily be controlled via a serial data connection located on the rear of the rig.  Unfortunately, the data level is not the standard RS-232 bipolar data output used by a PC serial port, so level conversion is required.

Fortunately for us, the RS-232 standard implemented in most PC serial ports is quite forgiving in terms of applied voltage.  In most cases, the serial input data does not need to swing below zero volts to indicate a change.  This makes it very easy to convert the data stream with simple components.

This circuit is typical of the many simple TTL/RS-232 conversion designs available.  The values of the components are not critical, so feel free to use whatever you happen to have in your junk box.  Just be careful about the 10K resistor connected to the +13.8V.  If the resistor is reduced too far in value, or if it is shorted directly to ground, you may find yourself having to replace R1235 within the FT-817!

Since the circuit is so simple, it's quite easy to build it "dead bug" style within a DB-25 or DB-9 connector shell.  Just make sure that you insulate all of the exposed wires from potentially shorting to ground or each other.  I accomplished this on my interface with a strip of cellophane tape wrapped around all of the components.

I have had no problem running this interface with a standard PC serial card for programs such as grig and gpredict using the default 4800 baud serial speed.  Running it off of a USB to serial adapter has not always as successful, no doubt due to the limited output voltages available to such devices.