Kenwood IC-10

A tiny interface kit that turned a late-80s HF transceiver into something a computer could actually talk to.

Overview

The Kenwood IC-10 isn't an audio component at all. Anyone expecting a tuner or an amplifier is going to be confused by the box. It's an IC kit - a small package of chips and documentation meant to be installed internally in the Kenwood TS-440S transceiver, giving that radio a path to computer-assisted control of its operating parameters. The manual opens by thanking the buyer for "the new IC-10 IC kit." That tells you how it was sold: not as a finished peripheral, but as a bag of parts and a promise.

The TS-440S already had the hardware hooks. The IC-10 supplied the logic. Once installed, control ran through the computer's RS-232C terminal by way of the IF-232C interface, which served as a level translator between the radio's internal logic and the serial port on the back of whatever PC the owner happened to own. The kit shipped with a μPD8251AFC IC and an instruction manual (B50-8081-10). That's the whole contents list - no cable, no software, no hand-holding.

The manual is explicit that the TS-440S does not include computer software. It says guidelines are provided, but with so many computers and languages in circulation, the owner was expected to design his or her own software package. In 1987, that wasn't a caveat buried in fine print. It was the entire proposition. You bought the IC-10, you soldered it in, and then you wrote the software that made it useful.

What the kit delivers is a command vocabulary. The manual's format tables lay out the instruction set in columns. There's a one-character switch field (0 for OFF, 1 for ON), a mode field where 1 equals LSB, a function field that selects between VFO A, VFO B, and MEMORY, and an eleven-column frequency field represented in Hz, so 00007200000 means 7.2 MHz. RIT frequency gets five columns, the first carrying a plus or minus sign and the remaining four the offset in Hz, so +1050 reads as +1.05 kHz. Memory channels take two columns, and a split specification field uses Q for receive and 1 for transmit. Kenwood's stated design goal was that the commands be interchangeable between different transceivers, cutting down on the software rework a developer would face moving from one radio to another.

The feature list in the manual leads with a wide variety of possible control instructions, a powerful and easy-to-understand instruction set, common commands shared across transceivers, and simultaneous operation of the personal computer and the transceiver. That last one is the interesting one. The IC-10 wasn't meant to take the radio away from the operator. The computer and the human could work the same rig at the same time.

Wiring it up took some care, and the manual spends a section on the precautions. Transceiver output goes to computer input and vice versa, with the example pairing the transceiver's receive data to the computer's receive data and the transceiver's RTS to the computer's CTS. The serial configuration is fixed: 4800 BPS, one start bit, eight character bits, two stop bits, no parity. Get the bit configuration wrong and nothing talks. The terminal connection table spells out the six-pin arrangement. GND is signal ground. TXD is transmit data out from the transceiver, using negative logic. RXD is receive data in, using negative logic. CTS is a transmit-enable input using positive logic, where a logic low stops transmit data. RTS is a receive-enable output, also positive logic, requesting inhibit when the level is low. Pin 6 is marked NC.

Two details in the command documentation matter for anyone trying to drive one of these today. When all effective frequency columns are zero, the memory is treated as an open channel. When a split channel is open, the transceiver defaults to the same transmit and receive frequencies, which is simplex. RIT handling carries its own warning. If the RIT frequency is set and then the knob is rotated again, the actual RIT frequency ends up different from the stored value, since the stored figure corresponds to the knob position rather than tracking it live. Software written without reading section five carefully will behave strangely because of that.

The IC-10 is a support item for one transceiver, sold as a kit, dependent on software the buyer had to write. The manual's own note that the TS-440S ships without software says it plainly. Owners who still have a working TS-440S and a copy of the manual can make one work. Everyone else is looking at a small bag of chips with a part number on it.