M7 GX Technical Manual
51
Raveon Technologies Corp.
9600 baud as at 4800 baud. Its performance is optimized for 4800 baud 2-level
modulation and 8000 baud 4-level modulation.
If 4-level modulation is used (8000 and 9600 baud over-the-
air), the “Modulation
Balance” procedure must be re-done anytime the radio frequency is changed. This
procedure must be done by a qualified radio technician. See section 10.7 for
details on how to do this procedure.
The maximum over-the-air baud-rate for a wide-band model (25kHz channel
spacing) is 19200bps. Due to IF filter limitations, it does not work as well at 19200
baud as lower data rates. Its performance is optimized for 9600 baud 2-level
modulation.
10.4.
TDMA Overview
TDMA, or
Time-Division-Multiple-Access
is a very effective way of allowing a lot of
radios to share one radio channel. Used extensively in GSM cellular and APCO
public-safety systems, TDMA excels at allowing quick and reliable access to radio
channels. It allows 2-10 times more radios to share a radio channel than
conventional carrier-sense methods. This allows 2-10 times more tracking radios
on one channel, as compared to radios that do not have TDMA capability.
The following diagram illustrates how it works.
When a
RV-M7 GX
wants to report its position and status, it waits until its assigned
time-slot, and then transmits its data. By default, TDMA time slot positions are
assigned by unit-ID, so
RV-M7 GX
with ID 1 uses the first slot, and ID 2 uses the
second slot, and so on.
A TDMA “
Frame
” time is the time it takes all units to transmit once. This is
configured with the
TDMATIME xx
command. The factory default is 10 seconds,
so every 10 seconds, each
RV-M7 GX
may transmit. The TDMA frame must be
set long enough for all units to transmit. For example, if you have 50
RV-M7
s, and
use 200mS TDMA slots, then the
TDMATIME
should be set to 10 seconds. The
