The Packet Radio
“
2 N 1
”
Handbook
by
Buck Rogers
K4ABT
Section 1
;
Packet Radio “The Basics
”
Section 2
;
The X1J4 System Node Operator’s (SNO) Handbook
ILLUSTRATION SECTION Charts & Node Drawings
TheNET
X1J4 System Node Operators Handbook
__ Page 58
The following steps outline the procedures to transform the MFJ-1270C REV 11 (shown on the previous page) into an X1J4 node
1.
Remove
jumper from all pins of JMP 9. Jumper may be used later in this TNC to X-1J2 node modification.
2.
Remove
IC U40. After the modification is complete, place U40 into a plastic wrapper and tape inside the front face-
plate for use if the node is ever returned to normal TNC service.
3.
Remove
jumper from JMP 15.
ADD
A JUMPER at JMP 16.
ADD
JUMPER at JMP 21.
4.
Cut trace
at JMP “X” Notice that tiny traces are close to JMP X: DO NOT CUT any other trace.
Cut ONLY the trace
between pads of JMP X
. Use extreme caution when cutting. This step is optional and may not be necessary unless you
are concerned with the node hearing itself in RF rich environments.
5.
If TNC is to be used as a GATEWAY between two frequencies or baud rates, insure that R14 & R15 are installed. If
they are not, remove the PC board and
add R14 and R15
. R14 and R15 are 100 ohms @ 1/4 watt each.
6.
To remove the PC board, remove the front face-plate (2 screws), then remove the screw which attaches Q3 (regulator)
heat-sink to the front of the TNC. Next remove the four (4) screws which hold the PC board in place. The locations of
the screws are shown in the drawing as a circled “X” symbol.
7.
Remove
the EPROM at IC U23.
CAREFULLY
install the new X-1J4 EPROM into socket at U23. BE SURE ALL
PINS ARE INSERTED INTO THE SOCKET. The number 1 pin is NOT left out of socket pin 1 as with earlier
revisions of this TNC.
This modification applies to MFJ-1270C "Rev 11" and later versions
.