MFJ-1270C/1274C MANUAL RADIO INTERFACING
Page 22
keying circuit are ICOM-2AT (tm) and Yaesu FT-x09, FT-x3, FT-727 (tm) and
others.
Appendix A at the end of this instruction manual provided pin designation for
some of the radios. Also consult the instruction manual of your radio.
If your HT has this type of microphone input, you can wire the microphone like
the one shown in Fig. 3-3 or you can remove the cover of the MFJ TNC and
install a shorting jumper at JMP L. Installing JMP L will eliminating the need of
soldering "Cx" and "Rx" to the microphone cable. "Cx" and Rx" are installed
on the MFJ TNC mother board. Fig. 3-4 shows the location of JMP L header.
On the MFJ TNC mother board, the "Rx" resistor for radio port is R140. If you
find the your radio still would not key properly after installing JMP L, it may be
necessary for you to change the value of R140 to a smaller value.
Be sure to remove JMP L when connecting the MFJ TNC to another type of
radio.
FIG. 3-3 HT Special Keying Circuit
FIG. 3-4 MFJ TNC JMP L Header Location
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