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Dare CR-3000/C
Field-strength meter with frequency counter

3000/C was a mobile frequency counter with built-in field-strength indicator, developed by Dare Instruments in Woerden (Netherlands) [1] around 1997 for the Dutch police. The units were used by the police to determine the frequency of mobile radio systems used by criminals in order to be able to intercept them. They could also be used to trace bugs and find beacon transmitters.
 
The unit has the form factor of a standard car radio, so that it could be built into virtually any vehicle, without attracting too much attention. It is powered by the 12V car battery (10-15V).

The CR-3000/C has a frequency range of DC to 1 GHz and will automatically lock onto the strongest signal when in close proximity of a transmitter. When locked, the 8-digit display will instantly show the frequency of the intercepted signal. When very close to the transmitter, the 8-unit LED bar to the right of the display will give an indication of the field-strength of that signal.
  
Dare CR-3000/C

It is currently unknown how many CR-3000/C units were made, but assuming that every police district in the Netherlands had between 2 and 4 units, we assume that approx. 100 units were built. In 1013/2014, the majority of CR-3000/C units were dumped on the Dutch surplus market. The handheld version, known as the CR-3000/H, has not (yet) been dumped.
 
Dare CR-3000/C Dare CR-3000/C The CR-3000/C in operation Rear view Connecting power and an antenna Connections at the rear Connections at the rear Operating the CR-3000/C at night

 
Controls
All controls are at the front panel of the CR-3000/C which consists of an aluminium panel with a custom-made self-adhesive keypad. A series of push-buttons at the lower half of the front panel are used to control the unit. The leftmost button is the ON/OFF switch. The display has two brightness settings: one for when the unit is used in bright daylight and one for use at night.

Front panel of th CR-3000/C. Click for a larger view.

The remaining black buttons (marked with up/down arrows) are for adjusting the threshold and sensitivity levels of the instrument, and for adjusting the volume of the acoustic indicator. When a speaker is connected at the rear, the unit will produce a tone of varying height depending on the strength of the signal, in parallel with the LED bar indicator at the front panel.

Rear panel of th CR-3000/C. Click for a larger view.

The image above shows the connectors at the rear panel of the CR-3000/C. The power socket accepts a wide range of DC voltages (10-15V) and was typically connected to the 12V battery of a car. Note that the sockets for the power input and the speaker output are identical. Do not swap them, as connecting power to the speaker output will permanently damage the audio amplifier inside the unit. The 1/100 output was intended for driving an external PLL, but it is unclear whether this was ever used.
 
Interior
The interior of the CD-3000/C can be exposed by removing 4 screws from the sides of the unit. This allows the upper and lower sections of the case to be separated, after which the interior becomes visible. The image below shows the interior or the CR-3000/C, seen from the rear.
 
The first impression is somewhat disappointing. One would expect a professional custom-made instrument like this to be a single integrated design, but instead it consists of a collection of separate PCBs, that were (probably) designed for other products and that were reused here.

The front-end was clearly designed for, say, an HF instrument, and is bolted to the bottom of the case. To the left of the front-end is a small PCB that holds the DC power converter and the audio amplifier. The main unit, mounted at the left, consists of three stacked and bolted PCBs.
  
Interior of the CR-3000/C

The upper PCB of the main unit appears to be nothing more than a cable adapter. The second PCB contains an Intersil ICM7216D [2], which is an 8-digit LED display driver / frequency counter. Despite the rather disappointing first impression however, the unit performs very well and does exactly what it was designed for. It can still be used as an intercept or measuring device today.
 
Interior of the CR-3000/C Interior of the CR-3000/C Keyboard and display controller Front end Power supply and audio amplifier Main unit The stacked main unit (note the small potentiometer at the bottom) Potentiometer accessible through a hole at the bottom

 
Block diagram
The block diagram below gives an impression of how the CR-3000/C works. The input signal is first amplified with a 2-stage wide band amplifier. The frequency counter inside the Intersil ICM7216D is suitable for frequencies between DC and 10 MHz, which is why the input signal has to be divided by 100 first. This is done by the pre-scaler, who's output is available at the rear.


The output from the pre-scaler is fed into the frequency counter, which drives the LED display. The output from the font-end is also fed into a detector that drives the field-strength LED bar indicator and the acoustic indicator (speaker).
 
References
  1. Dijkstra Advice Research & EMC Instruments BV (DARE)
    Company website. Retrieved April 2014.

  2. Intersil, ICM7216D
    FN3166.4. January 2004. Retrieved April 2014.

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