OES Engineers / qq22.net

(info page)updated 25/4/2019

Maxon DM200 MiniApp2 and DM200GPS modules.

Both of these units share the same diecast-aluminium enclosure. Although the
DM200 GPS version doesn't need the special screening-sections used for the MiniApp
version, or the mounting-holes for the MRF5015 f.e.t.

DM200 Versions / case

The DM200GPS

DM200 GPSDM200 GPS 2
This is a basic GPS receiver unit. It contains an old SIRF LXHA Gps Receiver
board attached to a motherboard containing the Voltage regulator, and RS232 driver.
The SIRF manual and info below pretty-much says it all...

The SIRF module is a 12-channel receiver which supplies it's data in NEMA0183
format. It provides a small amount of power to the antenna connector, so can be
used with either a passive or active GPS antenna. The antenna connection is a MCX /
SMA. I have a nixie-tube based clock here which I built many years ago. I'll be
using the dm200 GPS to auto-set the time on it!

DM200 GPS 3
I have linked to a couple of eveluation-kits that used this GPS Rx. They are
worth a read if you have one of these and would like to make sense of the data
on the serial-port. See the links below...

SIRF Dev-Kit pdf file .......................................... R-Tech Dev-Kit pdf file

The DM200 MiniApp2

DM200 MobitexDM200 MiniApp2
These are easily obtainable units found at radio-fairs and on the internet.
You can usually pick them up for a few pounds. The chap I got these from had
been stripping them for components, Well he used the empty case, and the PA-
Transistor for his other projects. and most of the other parts were scrapped.

According to the original specs for these, They are UHF covering a section
between 403 MHz and 460 MHz. Channel-spacing is 12.5/20/25 kHz and output
power is adjustable from 100mW to 10W. Modulation is GMSK and antenna is 50ohm
TNC. Below are some of the original Mobitex spec's which may be of interest.

About Mobitex pdf file ( how it all works...)
Technical characteristics and test conditions
ElectoMagnetic Compatibility (EMC) standards

Being a bit of an Old-School hacker, I decided to explore further...
If I can stretch the bands of these down a bit, they will be useful!
AND, as we can get to the PLLs programming pins we should be able to
get this thing to do some more interesting things.

Here is a basic line-up of the CPU board. (click below for the data-sheets).

NEC D70320 Micro Controller PDF DataSheet
Atmel AT29C020 Flash-Rom. PDF DataSheet
CML FX909AD /CMX909 PDF DataSheet
SGS Thompson TL064 Op-Amp DataSheet
Atmel AT93C46 E2PROM PDF DataSheet
KIA 358f dual op-amp PDF DataSheet

First, Off came the back. On went the marconi test-set and computer and I ran-
up a serial-terminal. When these units are connected to power nothing happens
This is due to the units going into power-save mode. They are intended for
remote and mobile applications, and leaving them on would shorten the life of
any battery based supply. After making voltage pin-voltage measurements with
the processor board attached and with it removed I traced the POWER-UP pin on
one of the 12way inter-pcb connectors, and traced this to a pin on the 25-way
D-Type connector. Pulling this pin low powers-up the DM200, so tests began.

DM200 CPU board

DM200 Radio board

I connected a logic-analyser to the pins of the 74HC244, and ran a simple
serial-analyser to take a look at the data-bursts from the DM. Connecting a
terminal to the d-type, along with my power-up adaptor, I could see data to
and from the DM200 at the pins of the '244. I have more than one of these,
so I took one apart and ran tests on the other. Made a list of any parts I
didn't already have a data-sheet for, and downloaded relavent info. So finding
the data, clock, LE and lock-detect pins on the 12-way header was easy.
I connected the analyser. I could see data/clocks etc,and the pll going into
lock. So, a good start.and only a couple of hours in.. COFFEE-BREAK...

Lineup for the RF board is as follows. (click below for the data-sheets).

LMX1511 PLL PDF DataSheet
LT1376 V-Reg PDF DataSheet
Motorola MC3371 IF/Disc DataSheet
BFG35 Transistor PDF DataSheet
BLT81 Transistor PDF DataSheet
MRF5015 PA transistor DataSheet
SGS Thompson TL064 Op-Amp DataSheet
MC7808 Voltage Reg PDF DataSheet

Initially I will use my universal PLL-driver to send data to the unit and check
out the RF stages for TX band-width and O/P Power, and RX performance. Then I
will make an adaptor to connect the cpu-board to my prom-programmer and read the
contents of the 29c020 for dis-assembly. If possible I'll re-use the cpu-board
to control the RF-board, by writing a routine in assembler and writing it to the
flash-rom. But I can always just design/make a suitable PCB to fit inside the
DM200 case and program a PIC to do the job, as I've already written many routines
in assembler to send data to PLL chips and LCD displays / read key-pads etc. This
would be a good way forward.

I may add a few more details to this page as time passes, and as I do more with
these. It's my intention to use them to scan through a section of the UHF band,
and produce transmit bursts for a project. I usually use high-power UHF-PMR
base-stations for this project, and my universal pll-driver, as it can be used
with various parallel and serial loaded PLL devices. And has keypad and display.

If you already hacking one of these and have a dis-assembly of the code,
or a schematic of the boards etc.. Please get in touch. SB (at) qq22.net Cheers. Ra.