es the Maxtrac will work on the 900 ham band. However the Spectra is much
harder. I have one Maxtrac converted and while getting to work took quite
some time the final mod is not that bad.
Start with a 900 Mhz Maxtrac. If is is conventional then fine, if not then
order FVN4019A conventional firmware. You will also need to order two Murata
filters (# DFC3R915PO25BTD) from a Murata Erie dist in your area. Locate two
chip caps with a value of 1.1 pf.
Install firmware if not already conventional. Remove the two Murata filters
in the front end and replace with the above so that the radio will pass 915
+- 12.5 freqs. Locate the VCO and using a LARGE solder iron heat the top
cover and pry it off. Now looking into VCO you will see that the small board
has components on left and right halfs and they are a mirror of each other
(the left and right). Looking in two corners you will see chips with chip
diode directly under it. It is very very tight in this
Remove these two chip caps that are next to the chip diodes. Replace with
the 1.1 pf caps *** NOTE: The value of these caps might vary -- you may have
to put anything from 1.1 to 1.9 pf in -- DO NOT use too much solder when
installing caps. It is very easy to damage the VCO!!!!
Now put everything back together. I have mine operating with a RX area of
920 to 921 and TX of 907 - 909. Programming of the radio will require Maxtrac
conventional software and when the program tells you the frq you entered is
out of band disreguard it and continue.
I am working on Spectra but not sure if this radio will make it. Anyone that
has info on the Spectra please contact me.
From: firstname.lastname@example.org (Dean McDermott - WB2CMN)
Maxtrax 900 Ham Conversion
Confirm that your radio had firmware FVN4019A. If not order this
from Motorola (510291S04). Using Motorola MAXTRAC (conventional)
software program ham freqs into radio. Software will warn that
freqs are not authorized, press F2 to continue entering ham freqs.
Once this is done perform VCO mods on next page.
After radio is programmed and VCO mods made radio should have rated
TX power but poor RX sens. This is due to the two 932 Mhz filters
in front end. Replace FL1 and FL2 with Murata DCF3R915P025BTD
filters. This will correct the condition.
Note: You will be working with CMOS!!!!! Use Caution!!!!!
VCO and Filter MODS are made on RF board.
Firmware chip is U804 on Logic board.
Maxtrac software can be bought from Motorola or a local shop
with software can program radio.
Motorola Maxtrac 900 VCO
: --//-- --//-- :
: (RX) (TX) :
RX VCO Mod
Remove RX cap, Remove TX cap, Place TX cap in location of original
RX cap. (Note- You may be able to leave orig RX cap in place and
add a large amount of solder to right side of cap while metering
Steering Line voltage. Add solder until S/L voltage is in the area
of 7 volts when radio is on your highest receive ham freq).
TX VCO Mod
After removing TX cap place a 1.7 pf cap in it's place. If this
value is not available you may place a high stability variable cap
of .5 to 4 or 5 pf in this place. If a variable cap is used you may
have to use metal tape to make a cover with a hole for the cap to
fit. Use as little solder as possable on the TX side. You should
have a S/L voltage of no less then 2 volts while transmitting on
your lowest freq.