| Jeffhs |
11-05-2011 03:40 PM |
Shortwave bands from roughly 1.7-10 MHz will always be nearly dead (except for stations in your local area or very nearby states) in the daytime. Your best bet for DX (distance reception) during these hours will be frequencies from 14 MHz (the amateur 20-meter band) up to 30 MHz. The lower frequencies (higher when spoken of in terms of wavelength in meters), however, will come alive after dark. Witness the standard broadcast band, on which you will be hard-pressed to find anything much other than your area's local stations during daylight hours. After local sunset, however, your AM radio dial will come alive with stations hundreds or even thousands of miles distant. I once heard an AM station (KOA-AM 850 in Denver, Colorado) one Sunday night after midnight Eastern time, after a local Cleveland station had signed off for maintenance; however, I can hear stations up and down the East Coast, the Great Lakes region, and part of the Midwest after the sun goes down in my area. Most of these are the big 50kW network-operated stations in New York and Chicago, although on occasion I have heard smaller (5kW or less) stations, using just a garden-variety 5-tube table radio (in my case, one in my collection -- a 1951 Zenith H511) with only the built-in loop antenna. I live in northeastern Ohio, 35 miles from Cleveland and close to western Pennsylvania, so I also often hear KDKA-AM 1020 in Pittsburgh at night -- and I also received WLS-AM 890 in Chicago at dusk our time on the Zenith set, which surprised me as most 5-tube radios are not that sensitive or selective.
The FCC has abolished what were once known as "clear channels" on the standard broadcast band to allow local-service stations in small towns or rural areas, many of which until this time had to sign off at sundown, to operate full-time with reduced power and/or restricted antenna signal patterns after local sunset. The original clear channels were set up in such a way that at local sunset, and until local sunrise the following morning, only two 50kW stations, typically one on either coast, would be in operation on those frequencies; daytime stations on the clear channels, if any, were required to sign off at local sunset to protect the so-called 50kW "senior" stations on the frequency from a phenomenon known as skywave interference -- the effect that allows you to hear distant stations on your AM radio after dark, but can cause real problems for other smaller stations on the same frequency. An example was station CKLW in Windsor, Canada, which also serves the Detroit area and is widely heard thoughout the eastern U. S. at night. In the clear-channel era, CKLW was the only station on 800 kHz in this country, so its 50kW signal was heard literally coast-to-coast. The abolition of the clear channels changed all that, with smaller, lower-power stations being allowed to operate full time as I described earlier; however, the new rules provide for protection of the 50kW big-city stations' signals from interference for a distance of 750 miles in all directions from the transmitter, meaning that any smaller stations within that range desiring to operate full-time must restrict their signal patterns and/or reduce power after local sundown, in some cases to well under 100 watts, so as not to interfere with the 50kW station. An example of this is a small oldies station about 35 miles from where I live. The station operates on 1360 kHz with 5kW daytime. It must reduce its power output drastically at night, however, to 57 watts and with a sharply directional signal pattern (directing its signal to the station's intended service area) to avoid interfering with a 50kW station in Cincinnati, Ohio (and possibly others) on the same frequency.
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