The Navigations-Funkpeilanhänger (2 achs.) - two-axled navigation radio direction finder trailer - (Ah. 447) was used on frontline airstrips for navigation of outflying and incoming aircrafts. It had a deadweight of 2,737 kg. (Image from D600)
This photo of the right side of a Navigations-Funkpeilanhänger (2 achs.) (Ah. 447) proves that this trailer had three windows per side. This is a good distinguishing mark to similar trailers. Note the mounted loop antenna.