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Maycom FR-100



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The Maycom FR-100 is usually marketed as an 'airband scanner'. In spite of that, it covers 66-470MHz in AM, FM-wide and FM-narrow, so this scanner is suited to be modified to monitor paging networks.

There is not much space to mount an additional chassis plug for the discriminator output. I have modified the headphone plug to connect the discriminator signal, keeping the headphone signal available as well.

Maycom FR100

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The discriminator IC is located at the back of the PCB in the scanner's top half. The board can be disassembled in three steps:

  1. Remove the washer from the volume potentiometer with a pair of fine tip pliers.
  2. Remove the solder of the antenna plug's ground and inner conductor. Use desoldering braid or a desoldering pump.
  3. Remove the three screws that connect the board to the housing. The right screw is partly hidden under the 10.7 MHz XTAL filter.

The top half of the scanner

The discriminator IC, a 10930, is a VSOP (Very Small Outline Package) IC. Its pins are spaced 0,5 mm (0.02''). A 'normal' SMD in SOIC (Small Outline IC), like the MC3361, uses a spacing of 1,27 mm (0.05''). The discriminator signal can be found at pin 12, on a corner of the IC.

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Pin 12 contains the baseband signal. The output is made on the middle contact of the headphone plug

A 10 k resistor connects pin 12 and the middle contact of the headphone output

The scanner uses a stereo 3.5 mm headphone output. The middle contact is used for the discriminator output. The solder pad indicated above is connected to this contact. A 10 k resistor is soldered to pin 12 of the receiver IC. Its other lead is isolated and connected to the chassis plug solder contact.

Using a stereo 3.5 mm plug, the headphone signal is available between the tip and ground. The discriminator output is available between the middle ring and ground.



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