N.S. 4a
(downed pilot emergency transmitter)

 

The NS-4 is a self-contained, battery-operated sea rescue transmitter. The apparatus is bright yellow; is is well designed, compact lightweight, buoyant and watertight. It is of sheet aluminum spot-welded together and housed in an aluminum box. Coils and capacitors (except the paper smoothing capacitors in the vibrator pack) are of ceramic material.

The vibrator is nonsynchronious, operating on a frequency of approximately 10 Hz. The armature is a light flat strip at right angles to the reed. The magnetic circuit is smaller and the driving coil larger than in the conventional vibrator. No rectifier is used, raw AC being applied to the transmitter so that the carrier will be modulated at the frequency of the vibrator and its harmonics.

The batteries are of the type originally developed for meteorological balloon transmitters. In tests, the 2-volt lead-acid batteries used for power supply dropped to 1.7 volts in 2 hours and 40 minutes; the 8-volt batteries dropped to 6 volts in the same time period. The estimated life of the batteries on intermittent use - 3 minutes on and 1 off - is 4 hours.

The device is an emergency transmitter "Notsendegerät" NSG 4 (sometimes NS 4), developed by Loewe-Opta in 1941. It could be worn attached to the pilot's suit. The NSG 4 transmitted on 58,4 - 58,8 MHz with 0,3 W. Two other versions of NSG 4, the NSG 4 c and NSG 4 d, having the same physical shape, transmitted on 42,0 - 42,5 MHz.

The receiver used for the homing procedure with NSG 4 was the FuG 141. The first design in 1940 was planned as FuG XVIII with a range of 58 - 64 MHz, but was realized in 1941/1942 as FuG 141 with a range of 58,0 - 59,2 MHz. This homing receiver ("UKW-Seenot-Zielfluggerät") was mainly installed in Do 24 T search and rescue aircraft. Later on, the frequency was changed to 42,075 - 42,430 MHz, and the designation of the receiver changed to FuG 141 c, the emergency transmitter changed to NSG 4 c. This lower frequency was within the overlap of FuG 16 and FuG 17.

(Description taken from LA6NCA's site and originally written by DF4SX, Joachim)

Link to LA6NCA's page

Link to Wireless for the Warrior

 
Specifications
 
YEAR INTRODUCED : 1941
   
FREQUENCY RANGE:
53.5 - 61.0 MHz
NUMBER OF CRYSTALS:
PRESET FREQUENCIES:
Two
ANTENNA:
Strip of copper-plate steel tape 1.5 m long and 25mm in diameter tapering to 10mm at the end . It is wound around the box and held in position by two clips when not in use. Unbinding the tape, automatically turns on the transmitter.
TUNING:(MO OR CRYSTAL)
MO
SENSITIVITY:
SELECTIVITY:
POWER SOURCE:
11 midget storage cells - 3 used in parallel for 2-volt filament supply, 8 used in series parallel for 8-volt vibrator supplies. Weight of the batteries - 400 grams - is about 1/3 of the total weight of the equipment.
SIMILAR SETS :
N.S.2 Notsender
POWER OUTPUT:(WATTS)
1 - 2 Watts
TUBES (TYPE and NUMBER):
2 - LS1 and LS2
USE:
Short-range sea rescue transmitter.
TYPE OF SIGNAL:
Modified continuous wave tone of approximately 400 Hz. A press switch "K" is probably used to key the transmitter for sending Morse.
RANGE: (MILES)
Operational radius to aircraft at 70 meters is 15 km; at
330 meters is 22.5 km; at 1300 meters, 64 km.
TO COMMUNICATE WITH:
TO REPLACE IN PART:
NS-2 which uses more critical materials and is used for longer ranges.
   
TRANSPORTATION:
Carried loose in aircraft for emergency use in sea. It can be secured to a person or a small boat.
 

 
The N.S.4a

 

 
Cover off - looks like the tuning adjustments have not been tampered with.

 

 
Inner contents. The box is waterproof.

 

 
The internal arrangement at another angle.

 

 
Antenna base.

 

 
Inside of the cover.

 

 
Schematic

 

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