Connecting an Icom Transceiver to your PC

PC control of an Icom transceiver is accomplished via a bidirectional CI-V bus, which uses an asynchronous protocol communicated via TTL voltage levels. Thus an interface between your PC and transceiver is required; the Icom CT-17 provides this function.

The basic function of the interface is voltage level conversion from the RS-232 levels used in a standard serial port (+12 and -12 VDC) and the TTL levels used by your transceiver (+5, and 0 VDC). The interface itself requires power, which can be provided either externally, or with some circuits by using one of the serial port modem control signals as a power source.

There are two decisions that will drive your choice:

1. do you want to use one of your PC's serial ports, or one of its USB ports?

2. would you prefer to build something or buy it?

Being able to choose #1 is a relatively new phenomenon. Previously, controlling a transceiver via USB port meant purchasing a USB-to- serial-port adaptor (e.g. from Belkin or ByteRunner) and connecting it to your interface's serial port. Now, however, there are off-the- shelf USB interfaces; see, for example 20interfaces.html . You can also build one of these yourself, as described in ; if you go this route, be sure to read the comments, as the circuit as presented contains an (easily correctable) defect.

If your PC has a spare serial port, or you'd prefer an outboard USB- to-serial-port converter, then you'll have many more choices with respect to the interface - down both the "buy it" and "build it" paths.

Alternative interfaces

[ K1NU interfaces]

[ Creative Services Software interfaces]

[ Donner Digital Interfaces]

[ ZLP Electronics CT-17 replacements]

You'll find product reviews of the above, along with more alternatives at .

Home-brew interfaces

Building a interface is a nice little project that can be accomplished in an afternoon, including the trip to Radio Shack and back. This circuit was published many years ago in QST; its very reliable, and you may already have the necessary parts laying around:

Another nice circuit,

uses the MAX-232 IC for level conversion rather than discrete transistors. It also includes a circuit to control your 706's PTT circuit using one of the serial port modem control signals, which you'll find convenient if you're planning to operate digital modes.

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