One year for Christmas I got a Zenith Royal 790 Super Navigator radio that had three bands on it, longwave, medium wave (the standard AM band), and shortwave. It was a great radio, although I was never able to get anything on shortwave (then again, I probably should have tried staying up late) and most of what I got on longwave were Morse code transmissions.
One summer night, I decided to try expanding my horizons beyond WLS, WCFL, and WMAQ (the station where White Sox and Loyola basketball games were broadcast) and started slowly advancing the tuning knob until I found something. As you can probably imagine, most of the “new” stations I found were Chicago-area stations, but out of nowhere, I found a baseball game: the Cincinnati Reds were playing the Houston Astros at the Astrodome. As the announcers talked a lot about the Reds, I figured out that this was a Cincinnati station, and it was: WLW at 700 kHz.
That was my introduction to broadcast DX-ing, the hobby of listening to radio broadcasts from cities other than your own, at a distance (which is what DX stands for, distance). The atmosphere helps a lot with it, especially during the summer: AM radio waves “skip” off the ionosphere and come down miles away, where they can be picked up by a standard radio. Depending on the strength of the station’s signal and the weather conditions, they might be heard hundreds of miles away. It’s not unheard of that a listener in California is able to pick up a broadcast from a station east of the Rocky Mountains.
The easy stations to try and hear are the clear-channel stations, North American stations that broadcast a signal of 50,000 watts. They’re called Class A stations and are protected as much as possible from interference from other stations that broadcast at those frequencies. So, a station at 890 kHz will either drop its power to 1000 watts or use a directional antenna to avoid interfering with WLS in Chicago, which is a Class A station with 50,000 watts of power. There’s a whole list of the Class A stations in the US, Canada and Mexico here.
I wasn’t a fanatic about broadcast DX-ing, but there are some people who go out of their way to try and hear as many stations as they can. When they find a station, they’ll send a letter to the station to tell them they heard their broadcast, along with what time they heard it and what they were playing or talking about then so the station can confirm that the person had actually received the broadcast, and then send the listener a QSL card, a confirmation that they had really heard them.
The most common forms of DX-ing are broadcast DX-ing on the AM dial or shortwave DX-ing, because AM radio waves used by short-, medium and long-wave stations propagate the best, but there are some hardy souls that attempt to pick up FM radio broadcasts or TV broadcasts (though I’m not sure how the move to digital TV affects that) from cities a couple of hundred miles away.
Incidentally, DX was also the name of a chain of gasoline stations, mostly in the Midwest, that was owned by Sun Oil Company (better known as Sunoco). Their gasoline contained boron (remember that?), which evidently helps car engines run better. Since I’m a sucker for old TV commercials, here are several of them for DX service stations.
This last one features the veteran character actor Jesse White, who was known for years as the Maytag repairman. He pops up a lot on vintage TV shows.