Filter
Top Products
MFJ-1278B MULTI-MODE APPENDIX F 2400 BPS PACKET
2400 BPS Receive Audio Setting
The MFJ 2400 modem employs automatic gain control (AGC) for its receive audio. The
receive audio level is pre-set for proper 2400 operation, and no adjustment is necessary in
most cases. If you set the receive audio of your radio properly for 1200 operation, then in
most cases will be suitable for the 2400 operation also. No adjustment for the receiver audio
on the 2400 modem board is needed.
2400 BPS 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-1278B 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-1278B. Note that these controls
set the transmit audio levels for all the operation modes of the MFJ-1278B, 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