ALRocker said:
I heard WIND 560 from where else, Chicago, for the first time here in N. Alabama a few nights ago. Clear as a bell for a few, and then it was gone.
That's pretty good, considering that WIND is non-existent in central IL at night! Their nighttime directional signal skews north-northwestward, toward Wisconsin with a slight null in your direction. So, I'd have to say that you had a great catch!
gar fla said:
I've been wondering about the difference between propagation over land as opposed to water as far as what the difference is, if any, between plain water and salt water. I always used to assume it was just any large body of water that would increase it but it seems that's not the case. Also, there don't seem to be DXing reports regarding the Great Lakes. Compare the signal coverage of two 50kw non-directional stations near water - WFAN and WLS. Notice the difference in land and water coverage for WFAN.
http://www.radio-locator.com/cgi-bin/pat?call=WFAN&service=AM&status=L&hours=U And now for WLS, where there's no difference at all.
http://www.radio-locator.com/cgi-bin/pat?call=WLS&service=AM&status=L&hours=U
Salt water provides better ground conductivity than fresh water; however, fresh water's conductivity is not bad by any means. MW signals do carry pretty well across the Great Lakes. An example of this is WHFB Benton Harbor, MI who's 5 kw daytime signal reaches many of Chicago's northern suburbs. A quick look at their expected coverage actually shows quite a difference in land vs. water coverage:
http://www.radio-locator.com/cgi-bin/pat?call=WHFB&service=AM&status=L&hours=D.
The thing with WLS and the other big Chicago AMs is that none are located on the water, as is the case with WFAN and WCBS - and groundwave propagation across Lake Michigan isn't going to assist them in picking up any additional listeners in-market. Remember that ground conductivity in the midwest is generally much better than it is in the northeast. So, it isn't that there is
so much difference in propagation between salt water and fresh water (yes, there is some) - in this case the details matter a lot too. Having your tx site right on Long Island Sound provides a straight shot across most of Long Island, southern CT and into most of NJ (across NYC). There, or in the low-lying Meadowlands, are two very good spots to put an AM transmitter because of the irregular geographical layout of the area. Remember that granite underlies much of the area north of Manhattan - and it has lousy ground conductivity. You'd lose a lot of range by sticking a 50 kw transmitter in Westchester, for example. Which is why none of the big NY signals are based there.
There is no such arrangement necessary in Chicago. Addison works just as well at reaching the market as Evanston would, if not better by being closer to the middle of the market. Not to mention that Lake Michigan is tiny when compared with the Atlantic Ocean. Not as much to be gained by being right on the lake. So, your example is a bit more like comparing apples and oranges than you may have initially thought.