AVS Forum Addicted Member
Join Date: Jun 2003
Location: Alexandria, VA, US
Mentioned: 3 Post(s)
Tagged: 0 Thread(s)
Quoted: 534 Post(s)
To add to what DrDon is saying (and because he invoked my name), often stations are pretty well boxed-in at their present locations. Yes, a station can move to another tower, but it may require a drop in power, or a directional antenna, or something else unsavory that would make you as a station engineer wonder if it's really worthwhile.
FM is particularly messy in my eye, doing everything by distance and contour calculations. FM stations can move even if they're boxed in like DrDon says, but as soon as you move out of the "distance protected" space, suddenly you have to do a contour analysis (I forget if the appropriate rule is 73.207 or 73.215 off-hand; pre-1964 short-spaced stations I think are 73.213) and start coming up with screwy directional patterns and other ways of managing things.
In TV you actually do a path-loss type analysis where signal is plotted to individual sample points. (I would know; the software for that is my day job at the FCC.) So you wind up having to deal with antenna patterns no matter what, which is a bit of a double-edged sword. On the one hand, it often means that small moves don't matter very much, because generally the path to each sample point isn't very different. On the other hand, and this is especially true in rougher terrain, it also means that tiny moves can create big changes if those moves change the path a lot because of line-of-sight differences.
But the bigger thing that's better in TV is that you can agree to accept interference as predicted by those analyses, something which I don't think FM can do. If you have stations who are willing to negotiate, it means often there's more latitude to move around as a result.
... I think I started rambling.
In any event, the repacking may result in stations realigning where they're transmitting from. The FCC is encouraging stations to share facilities to reduce the cost of the repack, so if it turns out that moving WWJ and WKBD to a common antenna at the WWJ studio is cheaper, it may very well happen. We won't know for certain what is happening for some time to come, though.
Comments are my own and not that of the FCC (my employer) or anyone else.
"Ignorance and prejudice and fear walk hand in hand..." - Rush "Witch Hunt"