When the three components are installed, the DTR line on the RS232 serial port may be used to turn the M7 data radio on and off.  The three components are R43, C21, and R12.  R43 should be a 1K 0603 resistor.  R12 should be a 10K 0603 resistor, and C21 should be a 680pF 0603 ceramic capacitor, 50V rated.

M7 I/O Circuit Schematic

To access the three components, the main circuit board in the M7 must be carefully removed.  Remove the 4 screws securing the front pannel, the two screws on the side and the four screws that hold the back panel on.  Then removed the one screw on the bottom of the unit that secures the voltage regulator.  Slide the PCA out of the enclosure.   

The location of the three components on the printed circuit board is shown below:

Once these components are installed, the DTR input will control the power supply of the M7 radio. If DTR input is below about 0.8V, the M7 radio will power off.  If DTR goes above about 3 V, the radio will power on.  In Sleep Mode 1, and external device must control the DTR line.  The radio cannot turn itself on or off.  If nothing is connected to the RS 232 serial port, the radio will be turned off, because R12 is a pull-down resistor, and will cause the radio to turn off if no signal drives the DTR line.

Once the modification is complete, re-assemble the M7 in hte reverse order is was disassembled.

To Reset the Password:

If you forget what the password is, you will have to reset the password. To do this:

1. Remove the back plate off of the M7 radio.
2. With the power on, momentarily press the Config button
3. You will get an OK prompt back from the radio, and it will be in the command mode.
4. Enter Password 0 to erase the password, and disable the password feature.
5. To store a new password, issue a Password xxxx command where xxxx is the new 2-7 digit password.

Many different types of batteries may be used with Raveon’s M7 series of GPS transponders.  This Technical Brief describes how well some common battery types will work with the M7 radios. 

Actual battery life will vary based upon how often the M7 GPS transponder transmits, but the data in this Technical Brief may be used to predict the battery life of most configurations.

Test Setup

For the tests in this brief, a UHF GPS transponder, model RV-M7-UC-GX was configured in GPS mode 2 to transmit its position every 10 seconds.  In GPS mode 2, the radio’s receiver is on 100% of the time, and the current draw of the M7 was an average of 90mA.  The peak current draw was 2.1 amps for 68mS each time the M7 transmitted its GPS position.

Summary Data

Duracell Alkaline

These batteries are the common Duracel batteries found at most department stores.

Test Result Summary

Initial Voltage:                                   12.57 volts

Voltage at ½ discharge:                   10.2 volts

Usable life (hours)                           18 hours

Voltage drop when transmitting       2.4V  (1.1 ohm resistance)

Approximate mAh capacity             1600mAh

Discharge Curve

Transmit Transient

The plot below shows the dip in voltage as the transmitter turns on and off.

Summary

The Duracell is an OK battery to power the M7 transponder.  But its high internal resistance will reduce the RF power output after the first few hours of operation.  The DC to the radio should stay above 9V while transmitting for full power, above 8V for 3-4 watts.

Energizer Lithium

These batteries are the common Energizer Lithium batteries for cameras and digital electronics found at many department stores.

Test Result Summary

Initial Voltage:                                      12.1 volts  (14V for a few moments)

Voltage at ½ discharge:                      12.0 volts

Usable life (hours)                              28 hours

Voltage drop when transmitting          3.5V  (1.6 ohm resistance)

Approximate mAh capacity                2520mAh

Discharge Curve

Transmit Transient

The plot below shows the dip in voltage as the transmitter turns on and off.

Summary

Even though the internal resistance of the cell is higher than the alkaline, the Energizer Lithium is a good battery to power the M7 transponder.  Its high internal resistance will not reduce the RF power output because its voltage is fundamentally fairly high.  The DC to the radio should stay above 9V while transmitting for full power, above 8V for 3-4 watts, so the 3.5V dip means the radio will have full power at 12.5V, and 3-4 watts out at 11V DC at the battery pack.

Lenmar R2G NiMH pack, 2150mAh cells

These batteries are Nickel Metal Hydride rechargeable batteries.  They were fully charged before the test.

Test Result Summary

Initial Voltage:                                      11.0 volts

Voltage at ½ discharge:                      10.3volts

Usable life (hours)                              17 hours

Voltage drop when transmitting          2.0V  (.95 ohm resistance)

Approximate mAh capacity                1500mAh

Discharge Curve

Summary

These batteries should be a good power source for the M7 GX transponder.

The internal cell resistance is low, but the voltage is also low. The RF power output stayed at full power for most of the life of the battery, dropping to about 4 watts at the end of the battery life.  The double dip at end of live was due to the fact the radio keep working down to 6 volts (albeit with almost no RF output because the RF PA is off), and the batteries keep putting our very low voltage for another couple hours.

This article describes batteries that may be used for an AVL system, but Raveon’s UHF Radio Modems may also be battery powered, so this article can be applied to these radios also.

Raveon Technologies Corporation

990 Park Center Drive, C

Vista, CA 92081

sales@raveontech.com

760-727-8004