Greetings,
It is possible / necessary to include the slot ID in a CQ call message at HF. At the expense of a few bytes it should be also possible to add the sender's "wait on slot" timer setting to the call. Currently it is assumed that the setting is 300 seconds (default). If a real setting of the CQ originating station is included, the station wishing to reply to the CQ will know whether it is too late or not.
73, Marek SP5ISZ