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AU-018
Universal UHF/FM bug receiver

AU-018 is a miniature two-channel crystal-controlled narrowband FM receiver, for the reception of a variety of covert listening devices (bugs), developed in the early 1990s by an unknown 1 manufacturer. The device works on two predetermined channels (A or B) in the UHF radio band. 2

The receiver measures 82 x 50 x 20 mm and weights 94 grams, battery included. It comes with two antennas: a 63 mm helical for short range, and a 170 mm ¼λ whip for longer range.

It is powered by an internal 6V miniature battery and delivers its audio to a miniature earpiece. The built-in noise cancellation (squelch) opens as soon as a signal is detected. At the bottom is a two-position channel switch, marked A and B, that selects one of the two built-in crystals. The formula for calculating the reception frequency is given below, and will be around 400 MHz.
  
AU-018 receiver

The receiver was suitable for the reception of a range of crystal-controlled covert listening devices (bugs), such as the AU-015 room bug, the AU-032 miniature bug and the AU-026 telephone bug [1]. Depending on the circumstances and the selected transmitter, it has an operational range between 300 m and 1 km. Note that the device is unsuitable for free-running bugs like the AU-020. The AU-018 receiver was available around 1991 for a price of US$ 485.

  1. Based on the choice of components, it seems likely that the device was made in Japan.  More
  2. Around 400 MHz.

Storage box with wireless phone bug
The various parts stowed neatly in the storage caes
AU-018 receiver
Receiver fitted with helical antenna
Receiver with straight antenna
Channel selector
Receiver battery
Earpiece
A
×
A
1 / 8
Storage box with wireless phone bug
A
2 / 8
The various parts stowed neatly in the storage caes
A
3 / 8
AU-018 receiver
A
4 / 8
Receiver fitted with helical antenna
A
5 / 8
Receiver with straight antenna
A
6 / 8
Channel selector
A
7 / 8
Receiver battery
A
8 / 8
Earpiece

Frequency
The reception frequency (fr) can be calculated with the formula below, in which fc is the frequency printed on the crystal. The crystal frequency is multiplied by 9 and added to the 10.7 MHz IF1.



Channel Crystal RX Frequency
A 43.100 MHz 398.600 MHz
B 43.1944 MHz 399.450 MHz
Compatible transmitters
The AU-018 receiver is suitable for the reception of a range of crystal controlled transmitters from the same manufacturer, that operate on the same frequencies in the UHF band. The table below provides a list of compatible transmitters and their prices in 1991 [1].

Model Range Description Price
AU-014 300 m Room bug in the shape of a pen $485
AU-015 1 km Standard room bug $485
AU-012 300 m Room bug in the shape of a calculator $485
AU-017 300 m Room bug in the shape of an outlet adapter $485
AU-021 300 m Room bug in the shape of a credit card $485
AU-052 300 m Room bug in the shape of an USB or HDMI cable $485
AU-062 300 m Room bug in the shape of an optical USB mouse $485
AU-032 300 m Miniature room bug $485
AU-016 300 m Room bug in the shape of a telephne splitter $485
AU-026 300 m Telephone bug (for analogue lines) $485



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Interior
The receiver is housed in a black aluminium enclosure that consists of two case shells. The rear shell can be removed by loosening the large bolt at the centre with a screwdriver or a coin, after which it can be taken off. This is the side when the 6V battery (V 4034 PX) must be installed.

The front case shell can be removed by taking out the recessed screw at the center of the shell. The receiver itself is covered by two aluminium shields: one at the components side and one at the solder side, held together with cellotape. The image on the right shows the components side of the receiver with the two shields removed.

The circuit is built around a Motorola MC3357P narrowband intermediate frequency IC [a]. It has an IF1 of 10.7 MHz and an IF2 of 455 kHz. Note that the circuit is nearly identical to the NFM strip of the 1985 Yaesu FRG-9600 receiver [2].
  
UA-018 interior

The output of the MC3357 is fed to a NJM386 audio amplifier IC made by JRC in Japan [b]. It is compatible with the western LM386. Based on the choice of passive components, the transistors and the NJM386 audio IC, it seems likely that the receiver was made in Japan. In the device shown here, most of the parts have date codes from 1991, but the Motorola IC is from 1997, which suggests that the device was in production for at least 6 years and probable longer.

UA-018 interior
Interior - top view
Front end
Local oscillator, IF strip and receiver IC
B
×
B
1 / 4
UA-018 interior
B
2 / 4
Interior - top view
B
3 / 4
Front end
B
4 / 4
Local oscillator, IF strip and receiver IC

Specifications
  • Model
    AU-018
  • Purpose
    Bug receiver
  • Manufacturer
    Unknown
  • Type
    Double-conversion FM receiver
  • Band
    UHF
  • Modulation
    Narrowband FM (NFM)
  • Channels
    2
  • Frequency
    A: 398.600 MHz, B: 399.450 MHz
  • Range
    300 metres to 1 km
  • Power
    6V
  • Battery
    V 4034 PX (4LR44)
  • Dimensions
    82 x 50 x 20 mm
  • Weight
    94 grams
Datasheets
  1. MC3357 Low Power Narrowband FM IF
    Motorola, Inc. 1996. Rev. 5.

  2. NJM386 Audio Amplifier IC
    New Japan Radio Corporation. Undated.
References
  1. Advanced Intelligence, Pocket size UHF Receiver UA-018
    Retrieved December 2021.

  2. FRG-9600 receiver, NFM unit
    Yaesu Musen Co. Ltd. Japan. 1985.
Further information
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Crypto Museum. Created: Monday 04 April 2022. Last changed: Wednesday, 06 April 2022 - 09:01 CET.
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