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It has been used with N1MMLogger and Logger32 quite successfully, in addition to QSORecorder.
Please note this device breaks absolutely all rules of good design and is absolutely not guaranteed to work, even if you had the very same setup.
This thing was made (I would not use the word "designed" to describe the process by which it came to being) to work without an external supply, even though the laptop only provides about +/7 V with very little current. It (the interface) provides both computer control and PTT control via a single port, and is small enough to fit inside a DB-9 shell (see picture below) except for the 100uF capacitor which is outside the shell, at the end of 1" long wires.
It looks like the transistor connected to TD (pin 3) is backwards, but it is not. It is used as common collector to increase the voltage across the 220 ohm resistor when the TD pin is high. The problem was that the kenwood has a small value pull-up resistor on the input, and my laptop's serial port does not have enough guts to create a low level.
The 220 ohm is sufficient to create a low level, and the transistor can bring the voltage up when the TD line is high. Because the TD line is mostly low, the capacitor is sufficient to create enough voltage across the 220 ohm resistor for successful communication. It would not work the other way around because the TD pin spends most of its time low.
With this interface, to get serial communication (such as if you wanted to use the interface with Logging software), you must make sure the RTS pin is set permanently high. This is not necessary with QSORecorder which does not use the TD and RD signals.
Picture of the Interface: