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The discriminator IC, a TK10421, is located on the IF Unit. This PCB is
mounted vertically on the main board. TP3 contains a signal that comes
from the discriminator. However, this signal is filtered too much to be
of use. Probably Uniden mounted an RC-filter with a cut-off frequency
of about 2 kHz. This causes the slopes of the digital signals to be
rounded.
A limiting resistor of 5.6 k has been soldered to pin 11 of the
10421. The exact value of the resistor is not critical; I use values
between 5.6 and 15 k. The resistor has been mounted on the side of the
IC, and fixated with a drop of glue from a glue-gun.
The inner conductor of a piece of shielded cable was soldered to the
other lead of the resistor. I connected the braid to the metal shield
of the coil on the other side of the PCB. The other side of the
shielded cable has been connected to a 3.5 mm chassis terminal at the
back of the scanner.
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