Pattern Changes, Power Cuts, AM Daytimer Sign-Offs

One of the first things a beginning AM (medium wave) broadcast band DXer should know is when your local stations either: A) cut from day power to night power (in some cases, vice versa), B) switch from day pattern to night pattern, C) a combination of A and B, or D) signs off the air for the day (regardless of whether it's sunset at the local station or the dominant station, or at midnight local time). Just as important is when the station A) increases (or cuts) from night power to day power, B) switches from night to day pattern, C) a combination of A and B, or D) signs on the air for the day (regardless of whether it's local sunrise or sunrise at the dominant station or 0600 local time).

As I write this, in the month of July, in the St. Louis area, daytime-only AM stations sign on at 0545, and sign off at 2030 Central time. For the full-time stations that operate with different power levels or patterns day and night, 0545 is when the station changes from night to day power/pattern, and 2030 is when the opposite happens. Some stations sign off one hour after sunset. Two of my locals, WEW 770 kHz in St. Louis and KFUO 850 kHz in Clayton, sign off one hour after sunset, to coincide with sunset at KKOB in Albuquerque, NM and KOA Denver, CO, respectively. Some stations sign off one hour before sunset, like KMMJ 750 kHz Grand Island, NE (to coincide with sunset at WSB Atlanta, GA) or WPEO 1020 kHz Peoria, IL (to coincide with sunset at KDKA Pittsburgh, PA). One daytimer that signs on one hour before sunrise is KCTA 1030 kHz Corpus Christi, TX (to coincide with sunrise at WBZ Boston, MA). There are also a few stations that switch to night pattern after sunset. WYLL 1160 kHz Chicago, IL switches from day to night pattern one hour after sunset, to coincide with sunset at KSL Salt Lake City, UT. Two stations change from day to night pattern three hours after sunset: WCKY 1530 kHz Cincinnati, OH (to coincide with sunset at KFBK Sacramento, CA) and WFME 1560 kHz New York, NY (to coincide with sunset at KNZR Bakersfield, CA). 

The period two hours either side of sunrise and sunset are prime hours to pull in DX. Depending on how far you are from the local station and the direction of the band opening, you can be able to pull in DX; the conditions are called sunrise skip and sunset skip. For example, KXSP 590 kHz Omaha, NE starts coming in behind a nulled KFNS Wood River, IL at least 45 minutes before sunset. My listening post is in a null from KFNS toward KXSP. The transmitter site for KFNS is located in Cottage Hills, IL, near Wood River. An hour before sunrise, the aforementioned KCTA 1030 kHz takes out WBZ and the other nighttime dominant on 1030 kHz, KFAY Farmington, AR. An hour after sunrise, stations to the west can make it in, like KBRL 1300 kHz McCook, NE, KTWO 1030 kHz Casper, WY or KRCN 1060 kHz Longmont, CO. Before sunset, I can hear stations from the East, Mid-Atlantic and Deep South, for instance. On a given day in that time period, WHO 1040 kHz Des Moines, IA could be taken out by WPBS Conyers, GA (which broadcasts primarily in Korean), WDZ 1050 kHz Decatur, IL (an ESPN Radio affiliate) could have its signal overtaken by WEPN New York, NY (on the Spanish equivalent, ESPN Deportes). After sunset, stations to the west with sunset times one hour later than St. Louis could make it in.

From 1988 to 1992, I lived on the Cherokee-Cobb County line in northwest Georgia, 25 miles northwest of Atlanta. Metro Atlanta has worse ground conductivity than St. Louis, so many Atlanta signals are inaudible at night. Two hours before sunset, Mid-Atlantic and Northeast stations start to come in, like WFAN 660 kHz New York, NY, WBT 1110 Charlotte, NC or WPHT 1210 kHz (then WCAU, later WOGL) Philadelphia, PA. Starting at sunset, Midwestern stations start coming in, such as WHB 810 kHz Kansas City, MO (then KCMO), KTRS 550 kHz (then KUSA) and KXFN 1380 kHz (then KGLD) St. Louis, MO, after WDUN Gainesville, GA and WAOK Atlanta, GA changed patterns. The farthest west I could get at sunset was eastern Kansas (notably KNSS 1330 kHz, then KFH, in Wichita). WCNN 680 North Atlanta, WQXI 790 and WAEC 860 Atlanta directed their night signals away from the Woodstock area (where I lived), so signals can come in from Memphis, TN and Pittsburg, KS at sunset. One night, I even nulled out WSB 750 after sunset to pull in KBNN (then KJEL) Lebanon, MO.

Turn on your radio starting at two hours before sunrise and monitor until two hours after sunrise. Repeat at two hours before sunset, and monitor until two hours after sunset. These time periods are excellent to pull in DX on the AM broadcast band.