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TSCM
TEMPEST
  
4F-130
RF leak detector - under construction

4F-130 was a portable RF Leak Detector/Attenuation Meter Kit, introduced around 1991 by Euroshield Oy (now: ETS-Lindgren) in Eura (Finland). It is intended for testing the performance of EMC shielding enclosures, such as the RF-shielded rooms inside embassies that are used for confidential conversations. The 4F-130 can be used as a countermeasures device (TSCM) as well as TEMPEST certification tool. A modern digital version of the 4F-130 is known as the MF-9F [2].

The set consists of a separate transmitter and receiver, each of which is battery powered and has its own collapsible magenetic loop (H-field) antenna. The transmitter operates at one of four fixed frequencies: 10 kHz, 156 kHz, 1 MHz and 10 MHz. The receiver has a built-in 8-bit micro­processor that uses FFT to compare its 40-200 Hz Intermediate Frequency (IF) spectrum with the sprectrum that was stored during calibration.

The relative magnitude between the measured magnetic field strength and the calibrated value, is then shown in dB on the analogue instrument.
  

Supplied with the set are two 30 cm measuring rods that can be fitted to the top of each loop antenna. They are used to ensure a fixed distance to the wall of the RF shielded enclosure under test. The manual [A] describes calibration and measurement procedures according to MIL-STD-285 1 and NSA 65-6 standards, differing only in the positioning of the two antennas (coaxial or coplanar). Note that this test set can only be used for measuring leakage of frequencies up to 10 MHz. For higher frequencies (e.g. 400 MHz or higher), different test equipment is required.

  1. Originally known as government specification MIL-S-4957A and used in the early 1950s for measuring screen mesh enclosures [A].

Storage case with 4F-130L leak detector set
4F-130L set inside storage case
4F-130 transmitter and receiver
4F-130L receiver with folded antenna
4F-130L receiver ready for use
4F-130L transmitter ready for use
Receiver controls and RF level meter
Transmitter controls
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Storage case with 4F-130L leak detector set
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4F-130L set inside storage case
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4F-130 transmitter and receiver
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4F-130L receiver with folded antenna
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4F-130L receiver ready for use
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4F-130L transmitter ready for use
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Receiver controls and RF level meter
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Transmitter controls

Features
The image below shows the complete system. At the right is the transmitter which should be placed outside the RF-shielded enclosure under test. It has an ON/OFF switch and a 4-position rotary switch for selection of the desired frequency. It is shown here with the antenna in operational position. At the top of the antenna is a plastic fitting for the measuring rod.


At the left is the receiver, which is housed in a similar enclosure. It has an ON/OFF switch, a MODE push-button and two LED indicators, plus an analogue meter which shows the path attenuation in dB. The receiver should be placed inside the RF-shielded room under test.


Setup
The diagram below shows the positioning of receiver and transmitter for each of the measuring standards. The transmitter is always placed outside the enclosure, whilst the receiver is inside. With the military standard MIL-STD-285, the transmitter and receiver are placed in a horizontal plane with the antennas facing each other. This is known as coplanar or in-line orientation.


With the NSA 65-6 standard, transmitter and receiver are placed vertically with the antennas in parallel on a common axle, as shown in the lower part of the diagram. This is known as coaxial or parallel orientation. It is believed that the NSA method provides more coupling between the transmission and reception antennas, and therefore offers a better indication of leakage.

For both standards, the transmission and reception antennas should be held 30 cm from the RF-shielded wall. The removable measurement rods can be used to measure this distance accurately. Any contact between the measuring rod and the metal shielding of the wall should be avoided.


Calibration is done in free space, with a gap between the tips of the measuring rods that is equal to the thickness of the RF shielded enclosure under test – as shown in the diagram above – and clicking the MODE button on the receiver. The devices can be placed on tripods for more stability.


Parts
Transit case
Transmitter
TX
Receiver
RX
Measuring rods
Operating instructions
Transit case
When unused, the transmitter and receiver can be stowed in the supplied transit case shown in the image on the right, along with the measuring rods, an instruction booklet and a screwdriver.

The case measures 465 x 390 x 187 mm and weights 8 kg with equipment, without batteries. Note that the transmitter and receiver should be stowed back-to-back, in order to avoid damage to the instrument (meter) and the controls.

  

Transmitter
The transmitter measures 275 x 150 x 48 mm and weights 1.7 kg. It is powered by 6 1.5V D-size battery cells that last approx. 10 hours. The transmitter operates at one of four frequencies, as set by the rotary selector at the front panel.

The transmitter should be placed outside the RF enclosure under test. At the top of the antenna is a socket for the 30 cm measuring rod, that can be fitted in one of two positions, depending on the measuring method (MIL-STD or NSA).

  

Receiver
The receiver is housed in a similar enclosure as the transmitter, and weights 1.8 kg. It should be placed inside the RF enclosure under test. It has an ON/OFF switch, a calibration button (MODE) and a large analogue instrument (meter).

Like with the transmitter, a measuring rod can be fitted to the top of the antenna to ensure a distance of 30 cm to the wall of the enclosure under test. During the measurement, the meter shows any leakage in dB.

  

Measuring rods
Two metal measuring rods of 30 cm each are supplied with the set. They should be fitted to the top of the two antennas, to ensure an exact distance of 30 cm between the antenna and the wall of the enclosure under test, in accordance with the MIL-STD and NSA standards.

Note that the measuring rods can be fitted in two orientations (up or forward), allowing a different orientation for each of the standards.

  

User manual
Each 4F-130 test set came with an instruction booklet that was stowed inside the transit case. Unfortunately it is missing from the set featured here, but luckily we were able to extract it from a 1992 evaluation report of the US Air Force [C].

 Download operating instructions
  

Storage case with 4F-130L leak detector set
4F-130L set inside storage case
4F-130L receiver with folded antenna
4F-130L receiver ready for use
4F-130L transmitter ready for use
Receiver controls and RF level meter
Transmitter controls
Two measuring rods
Close-up of the measuring rods
Measuring rod fitted straight up
Measuring rod fitted at 90 angle
B
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B
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Storage case with 4F-130L leak detector set
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4F-130L set inside storage case
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4F-130L receiver with folded antenna
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4F-130L receiver ready for use
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4F-130L transmitter ready for use
B
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Receiver controls and RF level meter
B
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Transmitter controls
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Two measuring rods
B
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Close-up of the measuring rods
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Measuring rod fitted straight up
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Measuring rod fitted at 90 angle

Block diagram
Below is the block diagram of the receiver, as it is presented in the user manual [A]. At the top left is the antenna which consists of three loops with two windings each, all housed in the same metal pipe (for electrical shielding). The antenna loops can be connected in series by means of a selector – depending on the selected operating frequency – under control of a the main CPU.


After buffering and (optional) amplification, the signal is mixed with one of four fixed frequencies – all derived from the same 10 MHz crystal – resulting in an intermediate frequency spectrum of 40 to 150 kHz. After filtering and further amplification this signal is then sampled by an 8-bit ADC and fed to the CPU which performs a Fast Fourier Transform (FFT) on it. The results are compared with the calibration values stored in the internal memory and converted to an analogue value using an 8-bit DAC, before being fed to the analogue meter at the bottom right.

The main CPU – an Hitachi HD6303RP – runs at 1.25 MHz, which is derived from the 5 MHz clock signal (10 MHz / 2). It is internally divided (in the HD6303) by 4.


Interior
Transmitter
The transmitter is housed in a two-piece enclosure that consists of two grey extruded aluminium shells, held together by brackets and a locking spring. To access the interior, the front and rear panels must be removed, along with the locking brackets and the spring. Note that the front panel also acts as the access to the battery compartment. Also note that the nut of the frequency selector must be removed before separating the case shells, to avoid damage to the selector.


The image above shows the interior of the transmitter after the upper case shell has been removed. It consists of an oscillator with four qauartz crystals, one of which is selected by means of the 4-position rotary switch at the centre. The signal is then boosted in a Power Amplifier (PA) before it is fed to the loop antenna. The latter is shown here in collapsed (storage) position.

Receiver
The receiver his housed in a same-size 2-piece aluminium enclosure, of which each half contains part of the electronics. The interior can be accessed by removing the front and rear panels, along with the locking brackets and the spring. The image below shows the opened unit with the two halves facing each other tête-à-tête, and the loop antenna in operational (unfolded) position.


Note that the two halves are interconnected by means of two fragile 14-pin flatcable connectors. Remove the connectors from their sockets before separating the case shells and be careful not to bend the pins. When re-assembling the unit, these connectors have to be reseated carefully.

At the right is the central processing unit (CPU), which is normally covered by a metal shield. It consists of an Hitachi HD6303RP 8-bit microprocessor running at 1.25 MHz, 2KB CMOS RAM and an 8KB EPROM that holds the firmware. Also present on this board are an ADC0833 8-bit ADC – for digitising the IF spectrum – and a DAC0808 8-bit DAC – for driving the analogue meter.

Transmitter battery compartment
Transmitter top cover removed
Transmitter interior
Transmitter antenna circuit
Transmitter detail
4-position frequency selector
Crystals
Transmitter interior, showing the frequency selector amidst other components
Note the nut that fixates the selector
Receiver interior
Metal shield covering the VPU
Microprocessor (CPU)
Front-end, mixer and amplifiers
Receiver battery compartments
Receiver top cover removed
Broken frequency selector
C
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C
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Transmitter battery compartment
C
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Transmitter top cover removed
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Transmitter interior
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Transmitter antenna circuit
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Transmitter detail
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4-position frequency selector
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Crystals
C
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Transmitter interior, showing the frequency selector amidst other components
C
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Note the nut that fixates the selector
C
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Receiver interior
C
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Metal shield covering the VPU
C
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Microprocessor (CPU)
C
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Front-end, mixer and amplifiers
C
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Receiver battery compartments
C
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Receiver top cover removed
C
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Broken frequency selector

Restoration
When we received the set, the transit case and both units (transmitter and receiver) were in good condition. Testing the transmitter revealed an intermittend problem however, that was clearly caused by the 4-position frequency selector at the front panel. Some frequencies did not work.

After opening the transmitter for investigation, the cause of the problem immediately became apparent. The contacts of the 4-position rotary selector are soldered to the PCB, whilst its shaft is bolted to the front panel. If the front panel is removed without removing the nut below the knob first, the selector will be torn to pieces.

Judging from the solder remains at the bottom of the PCB, this was not the first time, as the selector had clearly been replaced at least once before. In order to mount an attempt to repair the selector, it had to be removed from the PCB.
  

Normally, this would not have been a problem, but the questionable quality of the PCB, the lack of a soldering mask and the fact that the pins are soldered at both sides of the PCB, made it a real challenge. As the selector is obscured by several other high components, several parts had to be removed from the PCB to gain access to the upper side of the pins of the rotary selector.

After desoldering the legs – taking care not to damage the tracks and the through-plates holes – the selector came out, but immediately fell apart as shown in the image above. As it was beyond repair, it had to be replaced. Luckily, rotary switches of this type (MRC-204) are still available from several suppliers in the US.

Both sides of the PCB were thoroughly cleaned and a replacement selector was ordered. When it arrived a week later, its shaft was shortened to the required length. It was carefully positioned (not too high, not too low) and soldered in place.
  

Next, the unit was reassembled and tested by applying a 9V DC voltage directly to the battery terminals and switching the unit on. It immediately came to life and transmits an AM tone-modulated signal on any of the (four) selected frequencies. It is now fully operational again.

Problems
  • No manual
  • Broken frequency selector on transmitter
Fixed
  • Part of the original manual extracted from a US Government evaluation [C]
  • 4-position rotary selector replaced (transmitter)
Missing
  • Original manual
  • Original screwdriver
About Euroshield
Euroshield Oy was a manufacturer of high quality radio frequency (RF) shielding products used in the electromagnetic compatibility (EMC) industry, located in Eura (Finland). On 31 December 1997, Euroshield was taken over by ESCO Electronics Corporation in Texas (USA) for US$ 3.5 million, and merged into EMC Test Systems (ETS) [3]. In 2000, after the acquisition of Lindgren RF Enclosures, the name of the company was changed to ETS-Lindgren [1].


Specifications
  • Device
    RF leak detector
  • Purpose
    Testing EMC shielding (TEMPEST)
  • Model
    4F-130
  • Year
    1991
  • Manufacturer
    Euroshield
  • Frequencies
    4 (see below)
  • IF
    165 Hz
  • Attenuation
    0 - 130 dB
  • Accuracy
    ± 1.5 dB
  • Display
    Analogue
  • Indicator
    Battery check
  • Antenna
    Electrically shielded 300 mm loop (magnetic loop)
  • Batteries
    6 x 1.5V (each)
  • Life
    10 hours
  • Temperature
    0°C - +40°C 1 (Storage: -5°C - +45°C)
  • Dimensions
    275 x 150 x 48 mm (each)
  • Weight
    RX: 1.8 kg, TX: 1.7 kg
  • Accessories
    (see below)
  1. During calibration and measurement, the temperature must not vary more than 3°C.

Frequencies
  • 10.165 kHz
  • 156.085 kHz
  • 1.000165 MHz
  • 9.999835 MHz
Accessories
Documentation
  1. Euroshield RF Leak Detector 4F-130 - User manual
    Euroshield Oy, Eura (Finland). 15 pages. 1

  2. Evaluation of the Euroshield 4F-130 RF leak detector
    Dr. James R. Elliott, Henry S. Weigel.
    DTIC, AD-A251-606. 14 January 1991.

  3. Portable RF leak detector evaluations and UDRI/MRC HAMS refinements
    David A. Schafer, Gerald P. Chapman, Aka G. Finci.
    DTIC Wright Laboratory, AD-A258-819. 7 July 1992.
  1. Extracted from [C].

Datasheets
  1. HD6303RP CMOS micro processing unit, datasheet
    Hitachi. Date unknown.
References
  1. ETS-Lindgren, ETS-Lindgren History
    Company website. Retrieved 26 August 2021.

  2. ETS-Lindgren, MF-9F RF Test Set
    12 November 2019.

  3. Annual Report persuant to section 13 or 15(d) of the Securities Exchange Act of 1934.
    US Securities and Exchange Commission (SEC). Form 10-K, 23 December 1999.
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Crypto Museum. Created: Thursday 26 August 2021. Last changed: Monday, 01 April 2024 - 08:56 CET.
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