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Figure 2: Composite test signal circuit diagram

Using the circuit above and setting the signal generators to the levels shown in the diagram

simulates a CTCSS signal in a worst case condition. The performance of the DB1065 can be

measured with a SINAD meter connected to RXIN while each signal generator is varied to

simulate different signaling conditions.

4.5 Performance at other operating voltages

The DB1065’s performance may be evaluated at supply voltages other than the +5VDC supplied

from the on board regulator.

a. Turn power supply off.

b. Disconnect the power supply’s connection to J1 the B+ connection on the DB1065.

c. Set the power supply for an output of +5VDC.

d. Turn power supply off and connect it to the +5V J12 of the DB1065.

e. Turn on the power supply.

As an example, a DB1065 was configured to detect a 67Hz CTCSS tone using the following

configuration shown in Figure 3.

-

+

CTCSS tone @

30mvrms

Noise generator @

75mvrms, Band limited

6khz gaussian

1khz sine wave @

300mvrms

CTCSS tone

generator

Noise

generator

Audio signal

generator

.1uF

100K

.1uF

.1uF

100K

100K

100K

+Vdd

GND

GND

+Vdd

100K

100K

.1uF

To RXIN and

SINAD meter

Audio Opamp

741 or similar