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™The goal of this web site is to promote Packet Radio Networks and provide diagrams that will help the System Node Operator's (SNO) build more dependable Packet Radio Networks. The drawings and supporting text on this page are supported by proven methods that assure the best continuity of your Packet Radio networks. Additional information to support network node configuration is found on the node parameters page. The SEDAN SIG invites anyone interested to participate with us in building this system into a nationwide, high-speed, Packet Radio network.Attention; System Node Operator's, If your interests are in 9600 baud node building, then CLICK HERE, and go to the 9600 baud pages of this web site. 9600 baud ready radios, radio conversions, transceiver modifications,
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The single frequency node is the most popular type of Packet Radio Network node.
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The "GATEWAY" node shown here provides links between VHF/UHF frequencies and/or baud rates. By utilizing the "diode matrix" shown on another page, the System Node Operator (SNO) can establish several nodes into a "node-stack" that will link many frequencies, baudrates, and LANs. Most node stacks are limited to four nodes or less.
1. Remove jumper from all pins of JMP 9. Jumper will be used later in this modification at JMP 21. 2. Remove IC U40. After the modification is complete, place U40 into a plastic wrapper and tape inside the front face-plate for later use if the node is ever returned to normal TNC service. 3. Remove jumper from JMP 15. 4. ADD A JUMPER at JMP 16 (use jumper from JMP15). 5. ADD JUMPER at JMP 21 (use jumper from JMP 9). 6. Remove the TNC (stock) EPROM at IC location U23. CAREFULLY install your new X-1J4 EPROM into socket at U23. BE SURE ALL PINS ARE INSERTED INTO THE SOCKET (be sure there are no bent pins). Pin number 1 is NOT left out of socket as it was with earlier revisions of this TNC. This modification applies only to MFJ-1270C "Rev 11." 7. 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. NOTE "A": The photo shown above is an MFJ-1270C/Rev 11, and has the "MFJ-9600," (9600 baud) internal modem installed. The same mods apply to both 1200 and 9600 baud MFJ-1270 "C's."NOTE "B": Cutting JMP "X" is optional; If you are concerned with the node hearing itself and listing its own call and alias in its own node list, then CUT JMP "X". A problem occurs when JMP "X" is NOT cut and the node lists itself in its own node list. A user might inadvertently issue a connect request to the same node and find that they are connected again (locked) into the node. They may be required to issue the "BYE" command two times to be released.
NOTE "C" All MFJ-1270C/Rev 11 built after July 1996 have R14 & R15 installed. If they are not installed in your MFJ-1270C/Rev 11, they will not cause a problem unless you plan ot use the TNC in a node gateway, between two frequencies or in a node stack with a diode matrix. If R14 & R 15 are missing and your node IS TO BE USED between two frequencies or in a node stack with a diode matrix, then you should continue to steps 8 and 9. 8. 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. 9. To remove the PC board, remove the front face-plate (2 screws), then remove the screw that 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 photo as a red circled "X" symbols.
As a service to SNO's who do not have facilities to burn the X-1J4 EPROMs, we can provide top quality EPROMS for X-1J4 node use. To order theNET X-1J4 EPROM(s) for the nodes described in these pages, complete the form shown here.
CLICK HERE to view and print the EPROM order form
These PACKET Radio Network Node wiring diagrams are provided as a service for the PacketRadio system node operators who freely devote their time, money, and effort so that others may enjoy this wonderful hobby. The following pages of PacketRadio Network Node wiring diagrams are taken from my column, "the PACKET USERS NOTEBOOK" in CQ MAGAZINE. It is my sincere wish that the drawings, illustrations, and information in these pages will be helpful to the veteran SNO's and the next generation of Packet Radio System Node Operator's (SNO). CAVEAT!!! The drawings displayed in the following pages have been tested, however, I assume no liability nor responsibility for mistakes, errors, and omissions! Use these drawing at your own risk.
Thank You for viewing these pages. 73, de Buck Rogers K4ABT
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WebMaster, Buck Rogers K4ABT
TNX es 73 de Buck Rogers K4ABTCopyright 1996-2002 G. E. Rogers Sr and BUX Communications Corp.
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