www.BUXCOMM.com BUX 9600 baud Mods

Wiring pictorial to illustrate how two (2) nodes with DB 25 RS-232 ports are interconnected. Wiring pictorial to illustrate how two (2) nodes with DE9 (9 pin) RS-232 ports are interconnected. Tiny-2 or a DRSI DPK-2 DE9, nine pin RS232 comport to an MFJ-1270CQ/Turbo with a DB25 RS232 comport! The diode matrix is how the System Node Operator (SNO) can build several nodes into a "node-stack" to link many frequencies, baudrates, and LANs. Operate two (2) TNC or nodes into ONE (1) Packet Radio The five (5) step modification of the MFJ-1270CQ/Turbo REV 11 to an X-1J4 node. Conversion of the AEA PK-96 into an X-1J4 node Modifying the Icom IC-28 + for 9k6 baud operation. Drawings and Pictorials to modify the ALINCO DR-1200 for 9600 bauds. Drawing and Pictorial that enable simultaneous opertation of 9600 and 1200 bauds with the ALINCO DR-150. Kenwood "TM-251" interfaced to the Kantronics KPC-9612 for both 1200 or 9600 bauds KPC-9612 to the Kantroinics D-410, 430-450 MHz, High-Speed Data-transceiver MFJ-1270CQ/Turbo (300, 1200, & 9600 baud) TNC to the Kenwood TM-251 for use at 9600 bauds. Interfacing the AZDEN UHF Transceiver for Packet Radio use at 9600 bauds. Installing the "MFJ-9600," 9600 baud MoDem into the MFJ-1270"B" TNC Installing the MFJ-52B Deviation Meter into the X-1J4 node. The 'sniffer' (RF Probe) is a necessity when modifying Transceiver RF exciters. Modifying the GE DELTA SX transceiver for 1200 baud PacketRadio use. Modifying the GE DELTA SX transceiver for 9600 baud PacketRadio use. Modifying the GE Phoenix SX transceiver for 9600 baud PacketRadio use. Modifying the ERICSSON/GE Phoenix transceiver for Packet Radio use. Modifications to convert the Motorola MITREK(tm) into a 9600 baud, data-ready transceiver Mods to convert the G E MASTR EXEC II transceiver for VHF 1200 baud Data Modifying the Motorola Micor for VHF 1200 baud Packet use. The "MICOR MOD BOX" .. or,.. Down and Dirty MICOR to Packet conversion. A 'QWIK' Mod to put a VHF Mitrek on 1200 baud Packet. This mod improves the audio output to provide ample audio to nodes running 'open-squelch'. Need a more robust PTT (keying) circuit, this addition to the PTT line should fill the requirement.

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 build 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.

When ordering the add-on MFJ-9600 MoDem, be sure to specify revision 1.4 or later. Version 1.4 has Gated TX & Rx Eproms plus other enhancements for optimum performance.

Conversion of the AEA PK-96 into an X-1J4 node. The EPROM must be X1J code that is specific to the PK-96.

This text is primarily associated with the following drawings, however, the principle may be associated with any 9600 baud radio modifications. Much of the information found here is taken from the book I wrote in 1990, the title is, "The Packet Radio Operator's Manual" (PROM). It is still in print and available from CQ Publications; Phone (516) 681.2922.

Remember: Use shielded audio wire for the cables to and from the 9600 baud modem/TNC into the transceiver - one for the transmit and another for the receive, and keep them as short as possible. Don't try to make it work without the shielded cable, because it won't!

Because many of you will be using the readily available transceivers for 2 meters and above, try to obtain one with TRUE FM. These are usually the trans-ceivers that are crystal controlled, synthesized, and use a varactor modulator. Some are off the shelf, ready to purchase, such as the Alinco DR-1200 and the Icom IC-28, etc.

We will be connecting our transmit audio from the 9600 baud TNC/modem to the FM-modulated stage of the transceiver. When making this transmit audio connection, it is necessary to use a decoupling capacitor and resistor in series with the audio line.

In the illustrations on this 9600 baud page, I've drawn some of the circuits that will help you locate the correct interface points. I've included the same RC networks in the interface line of both the receive and transmit audio connections. The components in the RC network are identified in the drawings simply as C1, C2, R 1, and R2. For clarification, the capacitor (C1) value is in the range of 2 to 5 uF and of the nonpolarized type. Resistor (R1) value can range from 8200 ohms to 15K ohms. The role of the resistor is very important, as it serves to prevent extreme detuning of the varactor modulated stage.

If "padding" of the transmit audio is needed (unlikely), add C2 and R2 from the transmit audio line to ground.

Some Kenwood VHF and UHF transceivers are also being successfully used at 9600 bps. TR-751 receive audio connections are made to pin 9 of the TA7761P, or IC2 on the receive unit PC board. Use the 2.2 uF capacitor and the shielded audio cable we discussed earlier.

Transmit audio is injected to the FM modulator at the junction of resistor R81, varactor diode D21, and crystal Xl (10.695 MHz). Modifications for both transmit and receive are made on the receive PC board.

Although default parameters in the TNC will work okay, there are several which must be changed. Set the TXDelay between 14 and 18, or to no more than 200 milliseconds maximum. The FRACK can be set at 2 to 3 seconds, depending on channel congestion, 3 being heavy traffic and 2 being clear.

If you have a Mitrek manual handy, use it as a reference for many of these changes. Pop both the top and bottom covers from the Mitrek: 1 Locate the transmit audio amp/splatter section on the transmitter section similar to circuit board bottom view, upper left. Notice the last transistor... Q504 on the 39-50 MHz version, there is a trace that connects all crystal element, pin 4’s together. This trace is attached to the collector of Q504 via a small RF choke. 2 Next locate the transmit channel element(s). Locate pin four (4) on channel element F1 or # 1. NOTE: on the drawing, the line going to pin 4 of element #1 to the collector of Q504? Pin 4 of element will become the direct FM modulator input. Cut the trace at the channel element so that all other elements and Q504 are no longer attached. 3 Solder one side of a 1 to 2.2 ufd (non-polarized) electrolytic cap to pin 4 of the channel element F1(see note on drawing above). The opposite end of the 2.2 ufd capacitor is now your modulation input from the TNC. FSK line in the MFJ cable is BLACK. Attach (solder) shield wire to ground screw nearby (see drawing above). NOTES: If your Mitrek has the “tone-board”... remove it and toss it away! The tone board is a a piggy-back PCB about 3 by 5 inches, found in the near-left corner area (viewed front of radio facing you),top of unit (component side). ON THE ROCKS: We should have the crystals on hand to make this combo work. For a source of crystals you may try: We must have the crystals on hand to make this combo work. For a source of crystals you may try:

When installing the crystals into the element, note that the transmit and receive elements are different. DO NOT interchange them in the radio. It is also important that you install the transmit crystal into the transmit element and the receive crystal into the “receive” element. When soldering the crystals into the element, DO NOT overheat the wire leads of the crystal(s). Bend the crystal leads and seat the crystal into position before finally soldering the leads in place. Using the frequency counter and/or the centering meter, set (net) the radio to the center of your transmit frequency (see drawings above). In all the Mitrek’s that I’ve converted, I found that very little alignment of the RF and IF stages is required. If you are uneasy as to how to align the RF stages, then apply an on-frequency signal to the coax connector (input) and send enough signal into the radio to detect your (modulated tone) signal. If you get lost… move the large hex ferrite slugs to the top of the RF stage coils and begin again. In any case, use caution and the correct tuning tools to prevent breaking the “slug” inside the coils. If you’ve not done so already, be sure to “net” (peak) the receive crystal to frequency as soon as you have signal through the radio. A meter set to read AF level helps, or you may use the test points (J 1001 appears similar to a 9 pin tube socket) provided in the receive section of the radio. Pin 1 is from the detector (R222). “A point to read signal level (output).” Pin 2 is from the audio preamp (R234). “This could be a point to look at the discriminator output.” Pin 3 is from the “extender” if your Mitrek is equipped. NOW!; If all else fails, use the alignment procedure from the Mitrek manual. TUNING THE TRANSMITTER AND SETTING THE LEVELS:

This is where the "SNIFFER" described earler, comes into play!

After you tune the five coils in the transmitter exciter section; L701, L702, L703, L704, & L705, be sure to go back and set (net) the crystal to center the operating frequency… again. If you are as picky as I am, you may want to measure the exciter power output. Try to maintain the power at or below 1.5 watts into the RF PA section. A meter set to read RF level helps (the 'sniffer'), or you may use your VOM to read the test points at J1002 (appears similar to a 9 pin tube socket) provided in the transmit section of the radio. Pin 1 & 2 are GROUND. Pin 3 is from the “exciter” buffer output. Pin 9 is the Push To Talk line. When all else fails, use the alignment procedure from the Mitrek manual. Using an in-line watt meter that reads above 100 watts; Tune C804, C810, and C811 for max output… of course you are tuning it into a 50 ohm “dummy-load.” Remember… or keep in mind the power level that the radio was designed to deliver, and maintain the power at or below this level. When you set the 9600 baud deviation, use a 4800 hz tone from your IFR (or whatever you are using as a signal source. Make sure the tone deviation is set to 3 kHz no more, no less. If you don’t have a 4800 hx tone, then use the TNC with the tink set for 9600 baud DFSK out. Set the TNC (node) TXD to 120 and issue a bogus connect. This will key and modulate the radio with the 9600 baud signal. There are two ways to adjust the transmit deviation (Frequency Modulation). One way is to use the small nylon capped potentiometer (pot) on the 9600 baud MODEM board inside the MFJ-1270CQ Turbo. Another method is to use the pot via the large hole in the top of the transmit crystal element. To make you life simpler, set both the pot on the modem to ¾ open (clockwise) and set the pot on the crystal element for the same, ¾ full open (clockwise). Then use the pot on the crystal element to make the final adjustment for 3 kHz deviation. OH, BTW….: If you have already installed the

X-1J4 EPROM, then set MODE number 6 to 120 for the TXDelay period. After you have the transmit deviation set to 3 kHz, reset the MODE number 6 to 17 or for 170 milliseconds. One other note; In some older Mitreks,

spurious RF may be detected. To reduce RF leakage from the local oscillators in these MITREK, on the PC board (solder-side), add a .1 ufd ceramic cap from pin 1 to pin 3 of the transmit crystal element. Do the same to the receive crystal socket. You are about to make Packet Radio FUN AGAIN! 73 es Happy Packeting; de BucK4ABT

This "PacketRadio Users Notebook"1200 & 9600 baud radio modification page Updated August 9, 1998.

OK, ok... the "sniffer" RF Probe is back

It is an absolute necessity when modifying Transceiver RF exciters.

Modifying the ERICSSON/GE Phoenix transceiver for Packet Radio