I've just made a cable, using a Kenwood cable, but not the radioarena one. Unsurprisingly, it doesen't work.
However, i'm more interested in why it doesn't work and i've been doing some research on this.
As far as I can tell, an open-collector buffer is required to allow TX and RX logic levels to co-exist on the bus. It appears that some TTL drivers have this built in whilst others don't.
This document here, which details Dallas 1-wire protocol, suggests a circuit and describes how this vaiant of 1-wire serial works. I've also seen simpler, single-transistor buffer circuits online.
http://www.atmel.com/Images/doc2579.pdfI am guessing that PGDT use a simiar microcontroller to the atmel devices and hence also a similar comms protocol.
There are a selection of cheap (a couple of pounds or so) USB -> TTL devices on ebay. I know that some of these chispets support 1-wire, it's just a case of isolating which specific chipset does this.
I'll probably go ahead and order the radioarena cable, but I may also play with some of the above to see if I can get it to work.