Sunday, October 18, 2009

Re-programming an ICOM radio using a homebrewdata communication cable
(OPC-478 replacement)

I recently managed to get hold of (at very reasonable cost) an ICOM IC-F4GS PMR Radio (2-way walkie talkie) which had previously been used for (what I would imagine to be) nightclub security. No-doubt the bouncer who owned this had swapped it for a lightweight unit and an earpiece. The radio had three programmed frequencies.

So I have this great ICOM radio - Wow! Now what? Only having three channels programmed into it on unknown frequencies makes it pretty useless. So . . . I wanted to be able to re-program this radio for my own use on PMR446, and also perhaps the 70cm Amateur Bands.These radios are not programmable using the buttons on the front - You must program them using a PC, with specific software and a suitable cable.

The correct data cable for this radio (and for the IC-F3 radios too) was the OPC-478. I didn't fancy buying this cable. Getting it shipped over from a seller in China would cost £20-£25 (and a lot more it I got it from an official Icom retailer!) so I thought I would have a go at making the link cable myself.

Here is the circuit I used, with connection notes for a DB9, 9 pin serial plug.

The Data connection to the ICOM radio is via a 3.5mm Stereo socket, which is also used as the speaker / headphone socket. As you can see, the centre 'ring' of the plug is used as the data ('To Radio') and the connection to Ground is the outer. The centre 'top' pin is not used.
Similar to the Port Keyer that I had already built, I decided to build the entire circuit so it would fit neatly into the DB9 plastic housing. I knew that this would not be a straightforward exercise due to the amount of components I would need to fit into such a small space.

To save space, I decided to mount the two capacitors on the reverse side of the board.

Just for accuracy and completeness of the notes on this Webpage, it is worth pointing out that I exchanged the 1uF DC smoothing capacitor in the circuit for a 0.47uF one. This was due to not being able to fit a 1uF Electrolytic easily in the package. I also exchanged the 2, 33K resistors for 22K ones. This was just due to me having some spare miniature 22K resistors. These form the potential divider to Q1 and are not critical values.

I had to cut, trim, and melt the inside area of the plastic housing so that this circuit board would fit into it.The two parts of the housing would then be glued together.

This cable is also suitable for Programming Icoms IC-F11(s), F14(s), F21(s), F24(s) and F33/F43 (gs/gt)

As for the software needed - The correct software to use is ICOM's CS-F3G program (CSF3G).Here is the screen display of the software with the 8 Standard PMR channels programmed in.Note that the software is copyright and the property of ICOM. It is, however, available in several locations on the Internet.

Note - Using this Radio to TRANSMIT on the PMR446 frequencies is ILLEGAL (in the UK) as it transmits too high a power (This radio gives 1 or 5 Watts - The limit on the 446 band is 0.5W) - Couple with that, this radio is not 'Type Approved' for this band.As you can see, I have set the 8 PMR channels as 'Transmit inhibit' for receive only and the radio will only be used for my own test purposes. I intend to program the next bank or two in the set for 70cms Repeater channels.
I present this page for educational and informational purposes only. I make no guarantees regarding the accuracy of the information (although I have done my very best to make it accurate).The information presented here is of a project that I constructed and found working.


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