How to calculate the R12 & R15

1. Check the manual of your transceiver

What is the maximum deviation?
What is the packet input level of 9600bps?
What is the packet output level of 9600bps?

2. R12

Do not change the R13(180K) and C8(330p), because those C and R make the active filter (high cut off frequency is 2.688KHz.).
Do not use less than following value! And if this value is less than 100K, please check following condition (low cut off frequency)
First, you must check the cupping condenser of the packet output of 9600bps (C). (Ex. Yaesu's FT-7800 see red circle on upper left.)
1 / (6.28 * C * R12) < 20 (Hz)

2.1 When maximum deviation is more than +-2.5KHz.

R12 = 180K * (2.5KHz / (Maximum deviation)) * ((packet output level of 9600bps) / 600mv)

2.2 When the maximum deviation less than equal +-2.5KHz,

R12 = 180K * ((packet output level of 9600bps) / 600mv)

3. R15

Do not use less than following value!

3.1 When the maximum deviation is more than +-2.5KHz

R15 = 180K * ((Maximum deviation) / 2.5KHz) * (350mv / (packet input level of 9600bps))

3.2 when the maximum deviation less than equal +-2.5KHz,

R15 = 180K * (350mv / (packet input level of 9600bps))