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Make an OPC-478 / OPC-552 PC Cloning / CI-V cable.
By Brian, MW0GKX.
USB version
By Tormod Johansen, LA4ELA.

A lot of Icom transceivers can use a data cable to upload and download memory data and radio settings etc. to / from a PC with the relevant software through a speaker socket (check your manual).

Another use for this interface (with a slight adaptation which, I have discovered, turns it into the OPC-552) is PC control for many Icom radios using the CI-V socket (and suitable software, of course), well it works with my IC-737!

Schematic for OPC-478 Version 1

Parts List

R1 150 Ω.
R2 & R4 33 KΩ.
R3 47 KΩ.
R5 15 KΩ.
R6 4.7 KΩ.
C1 1µf 16 v.
C2 0.47 µf 16 v.
Q1 2SA1162 (BC557 or equiv.).
Q2 2SC3324 (BC547 or equiv.).
D1 5.1 volt Zener 1/2 watt.
D2 MA110 (1N418).
D3 1SS133 (1N418).
P1 9 pin D socket with shroud.
P2 3.5 mm Stereo jack plug.

Making Up

Although I've redrawn the original schematic that I have (with colour for ease of circuit tracing), some components have been altered by hand on that document. These alterations are shown (in brackets) in the Parts List. Whether they were altered by an Icom Tech, or by someone else "in the chain" before I got hold of the document I don't know.

You can use strip board, dead bug or even produce your own PCB if you like. Just follow the schematic. Component layout is not really critical for this circuit, although beginners (and the more experienced) may have to double check polarity / orientation of components. Between the circuit and P2 use some screened cable, this will help to keep out any interference.

Once made up check your soldering for bridged connections and wires for stray whiskers. If your construction is small enough it may fit in the shroud of the 9 pin D socket, if not a small box with short leads connecting to the 9 pin socket will work just as well.

Schematic for OPC-478 Version 2

Some PCs and USB to Serial adaptors can't power the original circuit. If you find that this is the case for you then use this modified version (right) which uses the same parts list. You will, in addition, need to supply it with 5 Volts DC from an external source.

Whichever version you build, to complete the OPC-478, connect P2 as:

Using the OPC-478 with your radio

To use the interface with your radio you will need the software relevant to your radio. This is usually purchased from the manufacturer or a third party. There are programs available from other sources, offering various features. Follow the instructions in your manual / software instructions or help file for connecting and data transfer.

If you need software for your radio but can't find any, take a look at: icomrecievers.narod.ru, there are lots of models listed and they're not all receivers (as the name would suggest). We cannot condone downloading and using commercial software, try before you buy is the name of the game.

Adaptation to a CI-V interface or OPC-552

I have found that my IC-737 can also use this interface, connected to the CI-V socket, if P2 is wired as:

In fact I've seen many mentions of this on various sites around the internet.

I have since discovered that with the circuit wired as above it becomes an OPC-552 as used on some other Icom radios!

I have actually gone a step further and wired P2 as shown in the schematic (original OPC-478) so that I can back-up and reprogram my IC-2725, IC-2800, IC-2820 and Denises' IC-T3H and, using a 3.5 mm stereo line socket some screened cable and a 3.5 mm mono plug, I have made an adapter for the device so that I can use it for the IC-737 CI-V as well:

OPC-478 to CI-V adapter

I have not tried to adapt this to a multiple connection CI-V for more than 1 radio, but it does work on a my IC-737.

Looking at the schematic for the CT-17 CI-V level converter, all you need to do for multiple device CI-V control is paralell the output connection (the CT-17 provides 4 connections).

For controlling the IC-737 I use: Ham Radio Delux which is FREE!!

Connecting to a PC without a serial port

I've been asked how to modify this cable to use it on a PC with a USB port and no serial port.

Short of purchasing or building a USB to Serial adaptor or purchasing an OPC-478U (has a USB adaptor built in) I have no other remedy.

I can report that the USB to Serial adaptor using the Prolific Chipset works well with this although Windows 7 had a problem installing the adaptor until I visited the Prolific website and downloaded the latest drivers.

Tormod Johansen, LA4ELA, writes:

I have successfully transfered settings to and from my IC-E90 by using a CP-2102 breakout board and a 1N4148 diode as the only external component.

Connections are:

Layout for USB Version using CP-2102
(image by Brian, MW0GKX)

The CP-2102 has TTL levels on the data signal already so no further level conversion is required. You can purchase the CP-2102 (or CP-2103 can be used also) from SparkFun.com.

Thanks for sharing that Tormod.

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