Limbaugh returns to WRKO

[Scott Fybush]

On 8/7/2012 3:52 AM, Bob Nelson wrote:
> I stand corrected about Entercom's other AM in Buffalo. And the 1520
> they have, WWKB, actually can sometimes reach our own area (even if it
> can't reach Rochester for some reason).

It's not "for some reason." It's for a very easily explained engineering 
reason. Any AM antenna system sends signal outward along two paths: a 
groundwave signal that travels along the ground for as far as the ground 
conductivity can carry it, and a skywave signal that shoots upward at an 
angle. During the day, the skywave signal passes through the ionosphere 
and out into space. At night, charged layers of the ionosphere reflect 
those skywave signals back down to earth at a distance.

Most of the time, those skywave bounces land at a distance beyond the 
end of the normal groundwave coverage. But on a fairly high MW frequency 
like 1520, from relatively short towers, the first skywave bounce lands 
quite close in - 75 miles in, or thereabouts, which puts it right over 
Rochester. And that's close enough that there's still a lot of 
groundwave signal present. Because the two signals arrive over different 
paths, they land out of phase, and it's that phase cancellation that 
makes 1520 hard to hear after dark in Rochester, just as it makes 1030 
hard to hear sometimes around Springfield, or WGY around Syracuse.

It's not so much that WWKB "can't reach Rochester" - it's more that it 
reaches Rochester by too many different paths at once!

s