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How do I configure an M7 repeater

The M7 transceiver has a built-in store-and-forward repeater function.  When enabled, any M7 series transceiver or GPS ttransponder may work as a repeater as well as perform it “normal” duties.  For example, if you configure an M7 GX ttransponder to be a base station, it will receive position messages over-the-air, and output them on its serial port to your AVL software.  The M7 GX may also have its repeater function enabled which, along with outputting the over-the-air messages on its serial port, enables it to also rebroadcast messages it receives back over-the-air.

Air Time and Slot Times

When any unit is configured to store and forward repeat, it will automatically rebroadcast the over-the-air position reports it receives, as soon as they arrive.  This repeating will occurs immediately after any message is received by the unit.

For example, on an M7 GX ttransponder running at 4800baud over-the-air, a position report takes about 70mS.  When a unit configured to repeat receives a position report message, it immediately turns on its transmitter and re-broadcasts the 70mS message a second time.  Thus, every position report will use about 140mS of air-time.  With encryption/decryption and other overhead, this actually takes about 160mS of air time for each message.

Each M7 GX transponders is assigned a TDMA time slot .  The width of the each time slot is based upon how much air-time it needs.  To send a GPS position report over-the-air at 4800 baud, the M7 GXo needs about 70mS, thus each transponder is typically allocated 100mS to send its position.

On a GPS tracking system that does not use a repeater, 100mS time slots works well.  But, if there is a repeater, each transmission will use about 160mS of air time, so the duration of a TDMA time-slot in a system with a repeater should be at least 200mS.  The SLOTTIME command is used to configure this parameter in the M7 GX ttransponder.

Enabling the Repeater Feature

The easiest way to enable the repeater is with the REPEAT command.  This works in M7 GX transponders with firmware B13 and higher.  Enter REPEAT 1 to turn on the repeater and REPEAT 0 to disable it.    REPEAT 1 command will configure the unit to repeat all messages it hears.

There is a more advanced way to configure the repeater.  In most cases REPEAT 1 is sufficient, but in certain cases the user may not want to repeat all messages.  For the case where only certain over-the-air messages from to to a certain ID should be repeated, the M7 GX ttransponder has a Repeat Table that may be customized for a particular application.

The repeat table as up to 4 entries in it.

Store-and-forward repeating is enabled with the ATXR command. ATXR 1 enables repeating. ATXR 0 disables repeating.  Once the store-and-forward repeater is enabled with the ATXR command, at least one entry in the repeater table must be configured.

A repeater table entry consists of 4 parameters:

 

 Source ID Messages from units with this Source ID will be repeated.
 Source Mask Additional address mask for the source
 Destination ID Messages to this ID will be repeated
 Destination Mask  Additional address mask for the destination

For a message to be repeated, it must match the Source ID/Mask and the Destination ID/Mask.

The Repeat Source and the Repeat Destination are programmed into a Repeater Table in the M7. The ATX command is used to program the Repeater Table. The Repeater Table may have up to 4 entries.

For example, to repeat only messages sent from ID 6 to unit with ID 150, the entry in the repeater table would be:

ATX1 0006 FFFF 0150 FFFF

Note the mask for an exact address match is FFFF.  FFFF means that all digits of the address are to be used.  Had the mask been FFF0, that would indicate the last digit should be ignored, and only the first 3 digits used to determine if the message should be repeated.

For example, to repeat all messages sent to ID 150 from ANY other ID, the entry in the table should be:

ATX1 0000 0000 0150 FFFF

By setting the Source mask to 0000, the source of the message is ignored, and only the destination will determine if the unit will repeat a particular message.

For example, to repeat all messages sent to ID 1 from ANY other ID, and also to repeat any messages sent to IDs in the range of 10-19, the two entrIes in the repeater table should be:

ATX1 0000 0000 0001 FFFF
ATX2 0000 0000 0010 FFF0

By setting the Source mask to 0000, the source of the message isignored, and only the destination will determine if the unit willrepeat a particular message.

To only repeat messages with a source ID in the range of 1-99, the source ID and mask would be 0000 FF00. The two Fs in FF00 indicate that only the first two digits of the source ID need match, and in this case they are 00.  The destination is ignored, so set it to all zeros.

ATX1 0000 FF00 0000 0000

The repater tablemay have up to 4 entries in it.  If an entry is not used, set it to 0000 FFFF 0000 FFFF.  The entry will then be ignored.  For example to only repeat messags from radios with IDs 12, 79, and 110, you could make 4 entries in the repeater table.

ATX1 0012 FFFF 0000 0000
ATX2 0079 FFFF 0000 0000
ATX3 0110 FFFF 0000 0000
ATX4 0000 FFFF 0000 FFFF

For example to only repeat messages from radios with IDs 12, 79, and 110, and also repeat any message to ID 1 you could make 4 entries in the repeater table.

ATX1 0012 FFFF 0000 0000
ATX2 0079 FFFF 0000 0000
ATX3 0110 FFFF 0000 0000
ATX4 0000 0000 0001 FFFF

Keep it simple.

The simple way to configure the repeater is use the REPEAT 1 command.  This will configure the table to repeat every message.

TO manually configure the table to repeat everything, enter these two commands:

ATXR 1  (Enables the repeat feature)

ATX1 0000 0000 0000 0000   (repeats every message it hears on the air).

One final note.  The repeat feature works independently of the rest of the radio.  The actual MYID, Group number, and TOID of the M7 do not affect the store-and-forward repeat function.

 

 

 

 

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