AFSK OUTPUT LEVEL
16
KPC-4 – AFSK Output – Jumpers K3 and K4
These jumpers are provided to alter the HF AFSK output level. The KPC-4 is shipped from the fac-
tory with the jumper in the LO position. The LO position sets an AFSK output level from the KPC-4
at 10 mV. The HI position sets an AFSK output level of 50 mV. Both levels are peak-to-peak values.
In general, transceivers requiring a pre-amplified microphone will also require the HI level AFSK
output from the KPC-4. Removing the jumper entirely will provide the maximum possible output
level of approximately 1.7 Vpp. Should you require an intermediate value of AFSK modulation sig-
nal, it may be obtained by replacing resistor R23 or R29 with the appropriate value chosen from
the following chart. If you change R25 to obtain an intermediate value, place the appropriate
jumper in the HIGH position.
470 Ω
2.2 kΩ
6.8 kΩ
22 kΩ
47 kΩ
470 Ω
2.2 kΩ
6.8 kΩ
22 kΩ
47 kΩ
24 mV
106 mV
290 mV
680 mV
1000 mV
KPC-2 – AFSK Output – Jumper K1
KPC-1 – AFSK Output – Jumper K3
This jumper is provided to alter the AFSK output level. The TNC is shipped with this jumper in the
HI position. The HI position output level is 21 mVpp. In the LO position output is 4.5 mVpp. If a
higher output level is required for your radio, it may be obtained by changing the resistor (R14 in
KPC-2, R37 in KPC-1). The chart below gives the output levels for different values of the resistor
with the jumper in the HI position.
100 Ω
220 Ω
470 Ω
1 kΩ
1.5 kΩ
2.2 kΩ
8.2 kΩ
100 Ω
220 Ω
470 Ω
1 kΩ
1.5 kΩ
2.2 kΩ
8.2 kΩ
4.5 mV
10 mV
21 mV
44 mV
65 mV
94 mV
298 mV
Should you require a still higher AFSK output level, the value of the resistor may be increased fur-
ther to provide incremental increases in the same approximate ratio as that shown in the table. For
maximum output level the HI LO jumper can be removed entirely. In this case, AFSK output level
will be approximately 1.5 Vpp.
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