DMP, also known by the military designator DR-PX-5A,
was a device for detecting and locating sources of electromagnetic interference
(French: Détecteur de Parasites) in the 200-500 kHz frequency range
aboard airplanes,
developed in 1951 by SARAM and manufactured by OMERA
(France), for use by the French Air Force (STTA).
In modern terminology it is an EMC detector.
The device is housed in a metal enclosure with black wrinkle paint finish,
that measures 205 × 180 × 220 mm and weighs 4.2 kg. It is built around a
SARAM 5-31 receiver that is located at the lower left, and powered by the 24V
DC network aboard an airplane, or an external battery.
At the rear are connections for a rod antenna or a loop antenna,
which are used for measuring the electric (E-field) and magnetic (H-field)
component of an electromagnetic signal respectively.
The image on the right shows the device with the CG-7-A loop antenna
fitted at the rear.
Apart from detecting and locating parasitic signals aboard airplanes, the
DMP reciver could also be used for finding and locating clandestine
transmitters (pirates) in the Medium Wave (AM) broadcast band
— especially in the vicinity of such a transmitter —
for example in combination with a
Automatic Direction Finder (also from an airplane) like the
ADF-T-12-C (190-1750 kHz).
DMP was first introduced in 1951, 1 and was produced in small quantities.
The device shown here was manufactured in 1955 and has a very low serial number
(56). Based on the surviving serial numbers, it seems likely that less
than 200 units were manufactured between 1951 and 1956.
106 copies of the manual were printed in November 1951 [A].
The diagram below gives an overview of the controls and connections of the
DMP receiver. All controls are located at the front panel. The 24V DC power
supply should be applied to the fixed shielded cable that leaves the
enclosure at the rear. At the right side are two sockets for connection of
a pair of 600Ω headphones. The strength of the detected signal is shown
on the large horizontal signal strength indicator at the top [A].
The bottom left quarter of the front panel holds an existing SARAM 5-31
receiver that is further described in a separate technical manual [B].
Applications
Detection and measurement of conducting interference onboard airplanes
Measuring the distance to a source of RF interference
Identifying and locating RF leaks
Measurement of parasitic emanations of onboard receivers
Locating clandestine transmitters in the AM broadcast band
The image on the right shows the bare DMP receiver without any antenna
connected. It has an L-shaped body that allows a square loop antenna
to be inserted at the rear.
Alternatively, a vertical rod antenna can be connected to the socket
that normally holds the loop antenna.
Loop antenna
CG-7-A
A square loop antenna (CG-7-A) can be installed in the antenna socket at
the rear of the L-shaped receiver body. When installed, it becomes an
integral part of the receiver.
The loop antenna is used for detecting the magnetic part (H-field) of an
electromagnetic signal in the 200-500 kHz range.
Rod antenna
The rod antenna consisted of three straight elements that could be combined
into one single rod, with the cable attached at one end. The antenna is
shown in the manual [A]. It was used for measuring the electric part
(E-field) of an electromagnetic signal in the 200-500kHz range.
The rod antenna is not available.
Technical manual
The DMP receiver was supplied with a full technical manual that includes
operating instructions ans well as the full circuit diagrams [A].
An additional manual is provided for the bare 5-31 receiver that is located
in the lower left quarter of the front panel and forms an integral part of
the DMP.
SARAM, the abbreviation of Société 'd Applications
Radioélectrique à l'Aéronautique et à la Marine
(Radio Applications Company for Aeronautics and Navy), was a research and
development (R&D) company, founded in 1936 by mr. Merles [1].
The company specialised in the development of (radio) equipment for use
aboard airplanes and ships.
Merles was born on 4 January 1905 in Ambert (Puy de Dôme, France)
and studied at the
Collège Godefroy de Bouillon in Clermont Ferrand and then as the Lycée Saint
Louis in Paris, before graduating at the Ecole supérieure d'Electricité.
He worked in the French Army as a telegraphy engineer (1930-1934)
and then at the company Bronzavia (1934-1936).
In 1936 he founded SARAM – an R&D company – which used Bronzavia for
manufacturing its products. When Bronzavia was no longer able to pay its
bills in 1949, Merles decided to set up his own manufacturing company
by the name of OMERA
— short for Optics, Mechanics and Radio.
From then on, OMERA manufactured the products that were developed by SARAM
and by its sister company SEPHOT (Société d'etudes photographiques).
As Merles had no children to leave his companies to, the decided to sell 70%
of OMERA to TRT in 1959, and the remaining 30% ten years later, in 1969.
Another ten years later, in 1979, SARAM itself was sold to SINTRA
(later: Alcatel), but merles remained its CEO until 1982.
Merles was also a director of the Société
d'électricité et de Piezoélectricité (SEPE) [1][2].
Specifications
Device
EMC Detector
Purpose
Detecting and locating parasitic RF emissions onboard airplanes
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Crypto Museum. Created: Saturday 22 November 2025. Last changed: Monday, 24 November 2025 - 11:08 CET.
