Jahnke began skating in 1985 because his friends played ice hockey. He won the novice men's title at the 1993 U.S. Championships. Around 1995, he broke two teeth in a skating collision with Dan Hollander while training in St. Clair Shores, Michigan. He was awarded bronze medals competing on the junior level at the 1995 and 1996 U.S. Championships and placed 19th at the 1997 World Junior Championships in Seoul, South Korea.