Direction Finding (DF)

Estimating the bearing to a transmitter — the RF layer’s answer to “where from?”.

Direction finding hardware estimates the bearing to an RF transmitter, typically with an antenna array comparing phase or signal strength across elements. Two DF sensors can triangulate a transmitter’s position; one gives you a bearing to investigate. Vendors commonly claim ±5° accuracy — real-world figures depend on multipath, antenna quality and mounting, which is why DF claims deserve the same scepticism as range claims. In the two-layer chain, DF on the RF layer complements the RID layer’s pilot-location evidence rather than replacing it.