Neil:

Time is one of the factors you're not taking into account. It takes time, and the variability of seasons and propagation to make most of the loggings possible. I would almost guarantee that I cannot hear all 8 stations I have logged on 1490 kHz in one night. In early winter I may hear a few that I can't at any other time of the year... same goes for late fall (thats Thanksgiving and New years: only 50 or so days apart). Time may permit changes in the sunspot cycle (5 years is significant: 2 or 3 will produce changes) to allow/disallow hearing some stations. iBOC has altered the ability to make confirmations by having a large bandwidth. The list of variables dependant on time are near endless, and all make or break station identification.

Paul S. in CT