The Commtel COM101 shows a lot of similarities with the Realistic PRO-57, both from the outside and inside. It is a 20 channel vintage scanner. The scanner gets a second life when it is modified with a discriminator output

The advantage of this scanner is that there is ample space to perform the modification. Furthermore, there's no need to solder directly to the discriminator IC.

The COM101

TP5 contains the unfiltered audio

The resistor and capacitor between TP5 and ground

TP5 connects to pin 9 of the KA3361. This is where the baseband signal can be found. A 10 k resistor is soldered to TP5. A 2.2 n capacitor is soldered to the grounded metal shield of an IF coil close to the IC. The other leads of the resistor and the capacitor are soldered together.

A piece of shielded wire connects the discriminator output to the outside world. The inner conductor is soldered to the joint of the resistor and capacitor. The braid is soldered to the shield of the IF coil. The other side of the shielded cable is connected to a 3.5 mm chassis terminal, which is mounted in the rear of the scanner.

Overview of the discriminator output