Complex sentence: "The Lincolnshire Poacher" was the nickname of a mysterious, powerful shortwave numbers station that used two bars from the English folk song "The Lincolnshire Poacher" as an interval signal.
Split into simpler sentences: The Lincolnshire Poacher was the common name given to a powerful shortwave numbers station. The station gained its commonly known name as it uses bars from the English folk song "The Lincolnshire Poacher" as an interval signal.