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Back to Home 		  Replacing the MaxTrac or
MaraTrac Firmware with
a Ham-friendly version

By Robert W. Meister WA1MIK 		  Print this Page


To do a proper job, you need to align the radio AFTER you replace the firmware, because the stock firmware only knows about the commercial bands and you're replacing the firmware to extend coverage to the adjacent amateur bands. This means you'll need a way to power the radio, run RSS, and connect test equipment to it. I find it easier to do this on the bench, where I have a spare control cable, control head, microphone, and speaker for the MaraTrac, along with an Astron RS-35M power supply, and all the required test equipment.

Make sure the radio is operating properly before you replace the firmware. You may have to adjust the transmitter and receiver VCO coils to insure full amateur band coverage, particularly on 6 meters where you may not get more than 8-10 MHz of usable coverage. If that happens, you should adjust the VCO coils for the amateur band and skip the adjustments for the lower portion of the operating band, i.e. the lowest four to eight alignment points or wherever the VCO refuses to lock up.

If your MaxTrac has the masked logic board, there is no firmware EPROM that can be replaced, as the firmware is embedded in the microprocessor. Select another radio or swap the logic board and go through the full board replacement procedure.

Replacing the Firmware:

MaxTrac:
Disconnect the power and antenna cables. Use a T-15 Torx driver to remove the two screws from the front panel. Use a T-10 Torx driver to remove the four cover screws (two on each side) and remove the two covers. On the logic board, pry the cover off the shielded microprocessor area. Use a small screwdriver and gently pry the firmware chip out of its socket in the left rear corner; it is the only socketed component in that area but there is another chip between the socket pins, underneath the firmware chip, so be careful. Note that there's a small "1" indicating pin 1 in the left rear corner of the circuit board and a notch in the chip along the rear edge marking pin 1.

Gently insert the new ham-friendly firmware EPROM into the IC socket making sure the notch in the chip is along the rear edge when you insert it. Push it down firmly. Install the cover back onto the shielded microprocessor area. Replace the covers and front panel.

MaraTrac:
Disconnect the control and antenna cables. Use a 2125 key to unlock the radio. Pull down the front handle and remove the radio from its mounting bracket. Push the button behind the handle and remove the top cover. Flip the radio over, mark the front of the bottom plate, and use a T-15 Torx driver to remove the bottom plate. Pry the cover off the shielded microprocessor area. Use a small screwdriver and gently pry the firmware chip out of its socket in the left rear corner; it is the only socketed component in that area but there is another chip between the socket pins, underneath the firmware chip, so be careful. Note that there's a small "1" indicating pin 1 in the left rear corner of the circuit board and a notch in the chip along the rear edge marking pin 1.

Gently insert the new ham-friendly firmware EPROM into the IC socket making sure the notch in the chip is along the rear edge when you insert it. Push it down firmly. Install the cover back onto the shielded microprocessor area. Install the bottom plate.

Aligning the Radio:

Set up the radio so it operates either on the bench or back in the vehicle it came out of. You'll need to attach a computer with a RIB and programming cable, as well as test equipment, to properly align the radio. Either a communications service monitor or individual pieces of test equipment can be used. On the bench I have a wattmeter, dummy load, frequency counter, audio tone generator, and deviation meter all connected and ready to go.

Remember that the MaraTrac has a fine power adjustment pot on the PA Driver board (between the RF board and PA assembly) that should be set to its mid-point before alignment. Also remember that a MaxTrac will get quite hot during alignment. Elevate it on something or aim a fan at the heat sink to keep it cool.

Connect and start RSS and go into the Service menu (F2). Choose Board Replacement (F6), Logic Board (F2). Go through the various screens listed below. Do NOT change or enter any data; press F10 to exit each one until you get to the TX POWER screen. You only need to adjust the TX Power and TX Deviation due to the expanded band coverage provided by the ham-friendly firmware.

Press F2 to Enter REFERENCE CRYSTAL DATA.
Press F3 to Set TX POWER.
Press F4 to WARP REFERENCE FREQUENCY.
Press F5 to Set TX POWER CALIBRATION.
Press F6 to Set TX DEVIATION CALIBRATION.
Press F7 to Set TOTAL DEVIATION w/PL.
Press F8 to Set TOTAL DEVIATION w/DPL.
Press F9 to Set TX DRIVE LIMIT CALIBRATION. (MaraTrac only)
Press F10 to EXIT Service Menus and Enter GET/SAVE to Archive Data.

Set each of the TX POWER soft pots for equal power on your wattmeter. I prefer to set it to a convenient value (20 or 40 watts for a MaxTrac, 100 watts for a MaraTrac); you can raise or lower it later. Remember that the frequency shown on the RSS screen will NOT be the actual transmitted frequency because the ham-friendly firmware now covers a greater frequency range in 16 steps, whereas the original firmware covered a smaller frequency range in these same 16 steps. More information is in the table below. Make sure you go through all 16 values. This time, press F8 to SAVE those values back to the radio.

Do the same thing with TX DEVIATION, pressing F8 to SAVE those values.

You can press F10 for the remaining steps until you get back to the main menu.

Here are the various band limits and step sizes in MHz for the MaraTrac. The MaxTrac is similar if not identical.

Band10m6m2m
ParameterLimitStepLimitStepLimitStep
Original 29.7-36 0.450 42-50 0.535 146-174 1.875
Ham-friendly 28.0-36 0.500 42-54 0.800 144-174 2.000

Finalizing the Alignment:

You can go into the Service menu (F2) and choose Alignment (F2), then either Deviation Adjustment (F3), Reference Oscillator Warp Adjustment (F5), or TX Power Adjustment (F7) as needed and tweak those adjustments until you're satisfied. I'd also suggest you go back to the Service menu (F2), Board Replacement (F6), RF Power Amplifier (F4) and run through all 16 alignment points again, just to make sure the power is the same at each point, because the power could vary slightly at a higher level. If you have to make any changes, remember to press F8 to SAVE those values. Get back to the main menu by pressing F10 as needed. Try some of your programmed channels and you should find the same output power and deviation on those as you did during alignment. It would also be a good idea to read the code plug from the radio and save it to disk.

Note that the Reference Oscillator Warp Adjustment frequency will be different than what is indicated on the RSS screen, due to the ham-friendly firmware. Consult the table below for the original and ham-friendly frequencies in MHz. In most cases the radio won't be more than a few kHz off, so it should be easy to figure out the correct frequency.

Band10m6m2m
Original 32.750 45.745 159.125
Ham-friendly 31.600 47.600 158.000

Reinstall the radio back into the vehicle and if necessary for the MaraTrac, connect an in-line wattmeter and set the fine power adjustment pot inside the radio for licensed power.

Contact Information:

The author can be contacted at: his-callsign [ at ] comcast [ dot ] net.

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This article was first posted 31-Oct-19.


Article text, artistic layout, and hand-coded HTML © Copyright 2019 by Robert W. Meister WA1MIK.

This web page, this web site, the information presented in and on its pages and in these modifications and conversions is © Copyrighted 1995 and (date of last update) by Kevin Custer W3KKC and multiple originating authors. All Rights Reserved, including that of paper and web publication elsewhere.