[Radio Wrangler]

Were there other ISB solid state receivers?

Yup.

Receivers were getting rather modular. Take the Racal RA1792. Usually thought of as a free-tuning general coverage receiver of high performance... but get the thumbwheel switch tuned version and it's really only good for point-to-point links. All versions have numerous choices of filter combinations, but there's also an ISB option with an AFC lock board.

Lots of parts in common with the general use receiver, but a full blooded ISB AFC machine for fixed links.

I used to have a Marconi H2900 - one of the prototypes to boot! Again thumbwheel tuned, had the full pack of 2MHz IF filters with USB and LSB in separate strips for ISB, with an AFC system for the synthesiser and a motor-tuned preselector inside it. This set was known in Marconi as 'Sosin's Folly' There's a lot of info on the web about B M Sosin and a very contentious comparison article in the Marconi company's journal. Litigation leading to letters from Marconi to librarians to destroy all copies, to be replaced by a redone version.

The H2900 was a deep, rack-wide unit about 9 inches tall. The one I had was milled out of a solid aluminium block. Marconi priced this above the ICS3.

There have been plenty of fixed link ISB receivers, and exciters (I used to use a Redifon GK203) but they lived quiet, isolated lives without much human intervention, and when sold off their switch tuning killed off most interest, though some enterprising traders made some front panels to convert them to the more desirable version.

David