Of all my AM DX catches, this is one of my favorites! XETRA was a Mexican station, licensed to Tijuana. Their studios were across the border in San Diego. Back in 1983, radio stations were prohibited from sending audio across the border from their U.S. studios to transmitters in Mexico. This rule applied to both phone line and microwave transmission. So, “The Mighty 690” simply tape delayed everything by 24 hours. The jocks would record their shows on Monday, the courier would bring the tapes across the Mexican border, and the shows would air on Tuesday. An early version of voicetracking!
I discovered this station the previous year when our family was vacationing in Southern California. With 50,000 watts on 690, they could be heard easily in Los Angeles, as well as further up the coast. But the night signal was directional to protect several other stations on the same frequency. On several occasions, I tried to DX this station from Minnesota, but no luck. KFI/640 in Los Angeles could be heard with no problems, so I knew my antennas were oriented correctly. But KFI was and is non-directional. It’s extremely difficult to hear an AM station from over 1,500 miles away when their signal is pointed away from you.
Then, one early morning at about 1:30AM, there she was! The Mighty 690! The signal’s not great, but it’s certainly good enough for a positive ID. Note the Legal ID in Spanish at about :33. A woman’s voice says “X-E-T-R-A, Ti-quana, Me-hee-co.” Then, “The Mighty 690” sweeper (English) into Styx’ “Mr. Roboto.”
Reception of this gem was made with a Pioneer SX-3900 receiver and horizontal longwire antenna, oriented SW/NE. I actually had to cut back on the antenna gain because of the noise overload. This is why the first part of this aircheck has a louder volume, then drops off as the recording progresses. A Technics stereo cassette deck and TDK D90 tape were also used.