Nick is correct - that pic was done by a well-known radio friend in the Netherlands.

729 was chosen in June 1983, after I had left (April) and John Kenning had left too(May, to start his Radio Sovereign)>. WHen I rejoined in August 83, 'New York' had chosen 729, balloons, vertical mounted turntables and etc.

The two Laser transmitters were both factory tuned to 729 KHz. The two transmitters for the other service were on 801. That's pretty close for a diplexer to keep separate ( >10% separation is preferred at those power levels)

558 was proposed and heartily promoted by an ILR engineer from Essex Radio who had a multiple agenda - one was to thwart the BBC using it for the new BBC Essex (opened the following year). He (rightly) predicted that we would get far better coverage on 558 even if only able to get a few kW into the aerial.