The electronics company R.F.Bech in Zurich built various simple near-field direction finders for the Swiss army. The owner was not only a radio amateur active since the pre-war years (HB9CE) but also part of the Swiss Army monitoring service from its earliest days.

The P-702 (Bech NP-1) was the first simple near-field direction finder with a range of 3 - 9 MHz, the P-713 (Bech NP-3) covered a range of 10.2 - 37.8 MHz. Both sets were only manufactured in very small quantities.

The only set produced in a „larger“ number of 27 sets was the NP-4S model (which later was known as the „Bech direction finder“).

• Fa. R.F.Bech on the website of www.radiomuseum.org