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PRO-2006 / COM-205


The Realistic PRO-2006 and the Commtel COM205 are similar. The scanner be opened by removing 4 screws on the back. Slide the complete case half a centimeter back, and remove the lid. I also disconnected the loudspeaker PCB-connector, which makes the scanner easier to handle.

PRO-2006 (top) and COM-205

There are 2 options for a discriminator output: directly to pin 9 of the discriminator IC, a TK10420. Or to TP2 (test point 2), which is connected to this IC directly. I chose for this last option, so that I didn't have to solder to the IC.

To facilitate working on TP2, I temporarily displaced the cable tree behind the big blue capacitor.



Two options for a discriminator output

Close-up of the simple RC-filter

TP2 consists of a 0 Ohm resistor, mounted vertically. I connected a 12 k resistor to the free end of this resistor.

Because the demodulated audio contained a small IF component, I connected a 2.2 n capacitor to the other lead of this 12 k resistor. The other lead of this capacitor is connected to the PCB ground plane around TP2. This creates a simple RC filter with a cutoff frequency of about 6 kHz.


The inner connector of a piece of shielded cable is connected to the RC-joint. The braid is soldered to the PCB ground plane. The other side of the shielded cable was connected to a 3.5 mm chassis terminal mounted in the back of the scanner.

After mounting the shielded cable, the cable tree can be restored to its original position.


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