Sutron Corporation Satlink Operations & Maintenance Manual, Rev 8.04.2 11/3/2016 pg. 106
10.4.2.1. Iridium Scheduled
Iridium Scheduled transmissions are much like Environmental Satellite Scheduled transmissions:
Settings Scheduled Time and Scheduled Interval are used to determine when and how often
Iridium transmissions are to happen. However, the choice of when to transmit is entirely up to
the user. The Iridium network is a commercial network and customers pay for bandwidth.
Unlike Environmental Satellite Scheduled transmissions, Iridium transmission do not happen at
the exact time that they were scheduled for. Instead, the modem is turned on at the scheduled
time. It takes the modem a little while (usually under a minute) to acquire a connection with the
satellites and complete a data transfer.
Additionally, Iridium transmissions are delayed by a random time of up to 30 seconds. This delay
is mean to prevent on-air collisions from multiple transmitters.
10.4.2.2. Iridium Alarm
When setup for Alarm transmissions, Iridium telemetry will send data as the station goes into
and out of alarms.
When the station enters alarms, an Iridium transmission will be sent. The measurement that
went into alarms should be configured with the Tx Data Content set to Last in order to make sure
that the reading that caused the alarms is transmitted.
10.4.2.3. Alarm Interval
This setting is relevant to Alarm transmissions only. If not zero, Iridium will repeat transmission
at the Alarm Interval for as long as the station is in alarm.
Additionally, if not zero, the Alarm Interval dictates the minimum time between transmissions. If
set to one hour, Iridium Alarm transmissions will not happen more than once an hour no matter
how often the station goes into alarms.
10.4.2.4. Max Tx Time
This value dictates how long Satlink will keep trying to reach the Iridium satellite network. If a
connection is not made during this time, Satlink will give up on the Iridium transmission and mark
it as failed.
10.4.3. Iridium Global Settings
These settings are found on the Other Setup tab of LinkComm. Please read on for a list and
description of each setting.
10.4.3.1. Iridium Listening
If enabled, Iridium Listening will cause Satlink to keep the Iridium modem on all the time. This
results in messages sent to Satlink being received near immediately. This reduces the data costs
associated with connecting to the Iridium gateway in order to check messages. In this mode,
Satlink will reset the modem once a day for reliability, resulting in at least one connection to the
gateway daily.
The downside to enabling Listening is increased power draw.
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