I recently obtained an ICOM V8000 rig from a fellow ham and decided to change the channel programming that he had been using to match that of my other rigs. Of course this meant that I needed to look into how to do this without punching a lot of buttons on the rig. I pretty quickly figured out that I needed a new OPC-478U cable and some software. The local Ham Radio Outlet had the software in stock (Dear ICOM: why can’t I buy this software and download it on-line?) so that was easy. But, they wanted $45 for the cable. $45 for a cable? Well, that dog won’t hunt! So, back to the web and my best friend, Google. I quickly found a plethora of schematics for clone cables. The schematics all indicated that the OPC-478U cable was nothing more than a RS232 to TTL level converter, so I decided “I can build that.”
Home Brewing the OPC-478U Radio Programming Cable Clone
I played with the idea of building a straight-forward RS232 converter but decided that this wouldn’t be elegant since the laptop I use for Ham operations does not have a RS232 port and thus I would need a USB to RS232 converter on top of the level converter. That led to a decision to use a common USB to TTL serial converter, also known as a “FTDI Friend” (see the parts list below for sources). Figure 1 is the resulting schematic.
At first, I bread-boarded this to make sure that it worked but, due to the age of the cloning software that ICOM provides (Windows 95/98 based!), it did not recognize my USB serial port at first. Older software such as this did not allow for more than a small number of Com ports, 4 in this case, so I had to manually reconfigure the USB serial port to one that it did recognize. If you run into this kind of problem, here is how to change it in Windows. First, go into Device Manager; select the serial port that you need to change. Click on Properties and then click on Advanced Properties. There will be a drop-down box available there to change the Com port to something in the range of 1 to 4. If they are all taken, select one that you know is not connected and ignore the resulting error message.
After getting the breadboard version working, I decided to make a more permanent version that I can keep in the toolbox for use when I change my mind about what frequencies to have stored. Figure 2 shows what that finished project looks like. The stereo cable connects to the rig and the micro-USB connector, as seen in Figure 4, provides the USB/serial connection to the laptop.
The FTDI Friend USB to serial converter board is available from many places such as:
- ZPS(TM) 3.3v 5.5v Ft232rl FTDI USB to TTL Serial Adapter Module for ~ $5
- Online from Adafruit p/n 284 for ~$15
- Frys OSEP FTDI, p/n 6997547, for ~$16
- Frys Parallax 28031-RT, p/n 522 9677, for ~$18
- Online from SparkFun p/n DEV-09 718 for ~$18
The rig connector can be from a cut-up stereo cable such as I used, like a Radio Shack 42-223, or you can use a 274-284 connector from Radio Shack and wire it up yourself.
The box used was a Radio Shack 270-283A, which includes a PCB that can be used to mount the circuit such as in Figures 3 and 4. This specific project box may be discontinued and unavailable, so choose something similar.
Use a 10K resistor or something close for the pull-up resistor R1. The diode I used was a 1N4148, but just about any diode should work.