MFJ-1270C/1274C MANUAL APPENDIX E: 2400 MODEM
Page 246
C. Transmit Audio Setting
Transmit audio on the 2400 board is set by adjusting R38 (next to T2) on the
2400 modem board. Transmit audio for the 1278BT is pre-set at the factory to
match the audio level of the 1200 modem on the MFJ-TNC mother board. Once
the 1200 and the 2400 transmit audio are set to the same level, then you may
adjust the audio level going into your radio by using the "Transmit Audio"
controls on the left side of the MFJ-TNC. Note that these controls set the
transmit audio levels for all the operation modes of the MFJ-TNC , including the
2400 packet operation.
When adjusting the transmit audio level please note that the range of R38 on the
2400 board is pre-set by CN-6 header. The shorting jumper on CN-6 header sets
range as follows:
CN-6 Jumper
Position
Transmit Audio Range
(no load)
no jumper 50 mV - 60 mV p-p
1 & 2 (default) 100 mV - 200 mV p-p
2 & 3 250 mV - 3 V p-p
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