Radio Yaguarí is the most common AM station from Bolivia here, and I have heard their signal on 1440 kHz a few times every summer since my first logging on July 19, 2010.
Late February this year I sent my third letter by air mail to Vallegrande, this time with a 5 USD note included. Still to my surprise I received an email, or actually three, from Maria Luisa Panozo Flores, Secretaria de la radio. She told me that the locutor I heard is named Lucio Arteaga Cabrera.
After my 34 years on the airwaves Radio Yaguarí is the second MW station from Bolivia I have heard.