Thanks for your thoughtful reply. I do intend to write an article on the restoration of our Challenger, and will cover the Challenger history in general by way of background.
With your three for Southern Shipping Corporation, we can account for 6 out of the 12 (or so) Challengers actually sold. However, the provenance of the one in Australia is unkown.
Our antennas are a 40 metre Inverted L for Transmit and a slightly shorter Long wire for receive. We have a stainless HF vertical to add to the antenna farm at some time in the future.
You are right about the Oceanic, although the one in the picture is a fully working example, I am very nervous about using for extended periods. I know this is contrary to shipborne use where it would have been on 24 hours every day. However, at the risk of digressing - we had (still have) another Oceanic, a dead one. Breifly, I believe the pathology before we obtained it was, 1) Stopped working one day, owner probably checked a few obvious things, turned it off and on a few times, 2) Finally disovered that the 5Volt rail had gone sky high, 3) Replaced the 5Volt pass transistor, 3) Still didn't work, sold it to us. I strongly suspect that the 5Volt Pass transistor failed short, rather than open, thus dumping 20(ish)Volts across the 90 odd TTL ics, all of which are soldered in - a nightmare to repair. According to my research, this is not an uncommon failure point with Oceanics. The pass transistor on our working one does get very, very hot, so rather then invite failure I avoid using it at present. A single TO220 style pass transistor for over 90 TTL devices is bound to be struggling. The long term intention is to fit an external, more substantial 5Volt supply with over voltage clamp and current limiting (both omitted from the Oceanic design). Aside from this shortcoming, it is a very capable and pleasant receiver to use.