====== P-713 ======
**Near-field direction finder P-713**, **Bech NP 3**; manufactured by [[Bech|R. F. Bech, Zurich]].

R.F. Bech, a Zurich based electronics company, developed several compact near-field direction finders from the mid-forties on.

Only three sets of the compact shortwave direction finder NP 3 (P-702) were made for evaluation by the Swiss Army monitoring.

{{:images:p-713.jpg?direct&600|P-713: Bech NP 3}}
===== Technical data =====
  * Principle]]: Near-field direction finder [[Bech]] NP-3: [[Single conversion superhet]]
  * [[Operation modes]]: [[A1]] ([[BFO]]), [[A3|AM (A3)]]
  * [[Frequency range]]: 10.2-16.1 / 15.7-24.9 / 23.8-37.8 MHz
  * [[Sensitivity]]: [[A3|AM (A3)]] / [[Selectivity]]: 

==== Power supply ====
  * [[Batteries]]: combined battery 126/6 V (LSA 126 6) for heaters and plate voltages

==== Dimensions ====
  * 340 x 470 x 220 mm, kg

==== Accessories ====
  * Frame direction finding antenna
  * Tripod
  * Bussole Recta


===== Operation =====
The shortwave direction finding receiver is built using a metal cabinet of the Zellweger radio station [[SE-105|P5 - Station]], in the bottom area, there is space for the combined heating and plate batteries LSA 126/6 (which were also used in the P5 station), the headphones and spare material.

Technically, it is a single conversion superhet with three band ranges 10.2-16.1 / 15.7-24.9 / 23.8-37.8 MHz, a [[BFO]] is provided for receiving carrier signals and CW stations.

The set is equipped with one [[KK2]] and six [[KF4]] valves.

===== Technical principle =====
Single conversion superhet, IF 450 kHz.

==== Tube configuration ====
[[KK2]], [[KF4]], [[KF4]], [[KF4]], [[KF4]], [[KF4]], [[KF4]]

==== Development ====
Three sets of the NP3 short-wave direction finders were developed in 1946. They replaced the [[P-702|NP1]] and became the predecessor of the "Bech direction finder" [[P-712|NP4]], a set that was introduced in 1946/7.

==== Deployment ====
From the mid-1940s, the company R. F. Bech, Zurich, developed several compact short distance direction finders; three single units of the NP-3 were built.

{{gallery>:images?p-713*.jpg&0&80x80&lightbox&showtitle&titlesort}}

===== Technical documentation =====
  * {{ :manuals:p-713-reglement.pdf |Bedienungsanleitung zum Peil-Abhorchgerät NP 3}}, KTA, 1947
  * {{ :manuals:p-713-instruktion.pdf |Instruction for the near-field direction finder NP 3}} with diagram and parts list, Bech AG, Zurich

==== Further information ====