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Motorola STX
Secure handheld radio

The STX was a series of handheld trunking radios operating in the 800 MHz or 900 MHz 1 band, developed by Motorola around 1991. Some STX radios have built-in speech encryption. The STX series was used by police forces and by the Ministry of Defence (MoD) of several countries in the USA and in Europe. The STX can be seen as one of the successors to the successful SABER series.

The image on the right shows a typical Motorola STX that is ready for use. About 2/3 of the body is taken by the radio itself. The battery takes about 1/3 of the hight and is attached to the bottom of the radio. A suitable antenna has to be screwed-in at the top panel that also holds the MODE selector and the volume control.

Also on the the top panel is a bright orange button marked EMRG. It can be programmed to send a distress signal in case of an emergency. If the radio is crypto-capable, the channel selector is used to select between secure and plain.
Motorola STX handheld radio

Peripherals and accessories, such as a speaker/mike or a covert vest, can be connected to the expansion socket at the left side of the radio, just below the antenna base. The socket is normally covered by a rubber cap that protects it against dust and damage. Just below the expansion socket is a fairly large Push-To-Talk (PTT) button that has to be pressed during a transmission.

  1. Most STX radios are 800 MHz models, operating between 821 and 870 MHz, but there are versions with the same factory ID that operate in the 900 MHz band.

Motorola STX Motorola STX handheld radio Top panel Display and keypad Emergency button Antenna Battery Operating the STX
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Motorola STX
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Motorola STX handheld radio
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Top panel
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Display and keypad
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Emergency button
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Operating the STX

The STX is a very compact radio, considering the era in which it was developed (early 1990s). The top panel holds the antenna, that is fitted with a screw-in terminal, the volume control and the MODE selector. It also features a bright orange distress button that is marked EMRG. The speaker and the microphone are both located at the top of the front panel. An external speaker/mike can be connected to the expansion socket at the left side. This socket is also used for programming.

Depending on the model, a display and a three or twelve-button keypad can be present on the front panel. When present, they are used to access the extended features of the radio, such as trunking and auto patch (connecting to an analogue telephone line).

Bringing an old STX radio back to life can be really difficult and is not for the faint of heart. First of all you need the correct Radio Service Software (RSS) for the Motorola STX, a Motorola Radio Interface Box (RIB) or equivalent, and a suitable programming cable. Next you need a DOS-based PC that is old and slow enough to run the software. And this is the really tricky part. Check out how we solved this in the past for the Motorola SABER, by using a very old Toshiba PC laptop.

Running the software in a DOS shell on a modern PC does not work, but apparently there is a program called 'DOS Box' which seems to be able to emulate an old and more importantly slow PC. Hints and tips on how to program a Motorola STX this way, can be found on YouTube [1].

Known accessories
  • NMN1004A
    Microphone with keypad and display
  • NMN1004B
  • NMN1004D
    Microphone/speaker with keypad and display
  • NMN6177A
  • NMF6050C
  • NLN8858
    Rapid charger (for single radio)
  • NLN8988A
    Rapid Multi Charger
  • HMN1015A
    Microphone/speaker (water resistant)
  • Converta-Com
    Mobile adapter with NMN1004D microphone
Expansion socket
The diagram below shows the pinout of the expansion socket at the left side of the radio when looking into the socket [2]. Connecting a microphone, speaker and Push-To-Talk (PTT) switch is pretty straightforward, as they are all connected against ground. The data line (7) can be used for programming the radio. To read the current version of the firmware, connect the data line (7) to ground (9) when switching on the radio. The information will then appear on the display [2].

  1. ?
  2. ?
  3. Microphone
  4. PTT
  5. ?
  6. ?
  7. Data (programming)
  8. ?
  9. Ground
  10. Speaker
Programming cable
The diagram below shows the pinout of the RIB/RSS programming cable for the Motorola STX. Suitable cables are difficult to find, so you may have to use the plug from an old microphone or speaker to make your own programming cable.

  1. Guerrilacomm, Programming Motorola STX & HT1000 Handhelds
    YouTube user. Surplus Radio Guide Series. 19 August 2014.

  2. Batlabs, Motorola STX
    Retrieved October 2016.

  3. Batlabs, RIB/Radio programming cable pinouts
    Retrieved October 2016.
Further information
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Crypto Museum. Created: Saturday 08 October 2016. Last changed: Saturday, 24 February 2018 - 14:03 CET.
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