If you think about when channel 30 was setting up shop in the early days, they had a different line of sight than they do today from the studios to transmitter site. I think WKNB was actually IN New Britain and the line of sight to Avon is not as good as it was to Farmington, and the original service area for the station was much closer especially for the harder to pick up UHF stations in those days and they might have felt it easier to reach the target market from Farmington. Plus they weren't trying to overlap the areas served by WATR. WTIC AM was already located in Avon and by the time ch 3 came to be the most logical choice for them would be on property they already owned in addition to being line of sight. Of course I'm not entirely sure how they did studio to transmitter links in those days, I'm assuming it isn't much different than some of the systems I had to use back in the mid-80's (though the stuff at the station I was at was not a over-the-air STL, I am somewhat familiar with the equipment of that time). As for the other stations, just like most of radio chose Meriden Mountain, the remaining TV stations seem to choose the Avon site.