A while ago I picked up this modem and I have finally got around to digging a little deeper and in particular scanning the documentation for archive.
So it seems the device was supplied by R. A. Sadler (G1SFK) in may 1989. In the letter supplied with the kit it mentions “if yours is of the new type 64C then you may find problems with the TX data” So this line in the letter shows that the 64C was brand new at the time 🙂
Schematic of the circuit using the AM7910 Chip.
Template for the PCB. It should be possible to etch a new one from this. In the PDF documents below it is to scale when printed on A4.
Component layout of the board and details of how to assemble the Commodore 64 tape connector.
Here are some photos of the insides of the device and the very scrappy cables which I will probably rebuild before connecting this thing to a C64.
The PDF has the original notes / instructions sent with the kit and hi res scans of the schematics etc:
These are sort of pointless but for the purposes of archive these are some notes the previous owner included.
Finally some interesting links that relate to this set up which will aid me when I attempt to get this running.
Two documents that describe the system:
This link has downloads and documentation for the packet radio software (Digicom v5.00).