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De-emphasis for

APRS (TNC-2, etc)

By Larry Higgins, W5EX

The Delta discriminator output at 2200 Hz is down 0.8 dBm from the 1200 Hz tone.

Speaker output has a 2200 Hz down 9 dBm from the level at 1200.

I found that be best combination so far, designed to give a small advantage to the higher

tone is: an L-network, capacitance in shunt; resistance in series with the discriminator,

feeds cap.

Values: 130 ohms (5%) and 0.9 uf. (The actualvalue of a ceramic cap marked 105).

This allows the 2200 Hz signal to be 0.25 dBm hotter than the 1200 Hz signal.

Using a service monitor input, I can simulate the Tiny Trak by feeding 1.56 Hz deviation

at 1200 and 2.37 Hz deviation at 2200 Hz.