CTCSS Signalling Processor

FX818

© 1997 Consumer Microcircuits Limited

6

D/818/4

1.4

External Components

C1

22pF

±20%

R1

1M

±5%

X1

4.032MHz

±100ppm

C2

22pF

±20%

R2

100k

±10%

C3

100pF

±20%

R3

100k

±10%

C4

0.1µF

±20%

R4

Note 2

±10%

C5

100pF

±20%

R5

22k

±10%

C6

0.1µF

±20%

R6

Note 1

±10%

C7

Note 2

±20%

C8

0.1µF

±20%

Notes:

1.

R2, R6 and C3 form the gain components for the Summing Amplifier. R6 should be chosen as

required from the system specification, using the following formula:

Tx Sub Audio Gain

=

−

R2

R6

2.

R3, R4, C5 and C7 form the gain components for the Rx Input Amplifier. R4 should be chosen

as required by the signal level, using the following formula:

Gain

=

−

R3

R4

C7 x R4 should be chosen so as not to compromise the low frequency performance of this

product.

Figure 2 Recommended External Components