Campbell Scientific ST-20 Argos Satellite Transmitter - Manual (Page 10)

ST-20 Argos Satellite Transmitter
The ArgosDataRepeat instruction is most useful when only using 1 ID number
because time between each buffer transmission is the rep rate. When using
several ID numbers for each platform, the ArgosTransmit instruction allows
the datalogger to control the timing of each transmission.
If a buffer is set to transmit, but the buffer has not been setup with valid
parameters, ArgosDataRepeat will fail.
2.4 ArgosTransmit
Usage: ArgosTransmit(Result Code, Buffer Number)
2.4.1 Result Code
The Result Code is a numeric variable that is set true (-1) when the
ArgosTransmit instruction is successful.
2.4.2 Buffer Number
The Buffer Number designates which ST-20 buffer is transmitted. Valid
entries are 0 through 7.
ArgosTransmit is used to initiate a single transmission immediately. One must
be careful because the datalogger program is totally responsible for the actual
repetition rate when using this instruction. Works well for those with multiple
ID numbers needing more data throughput and total control over the timing of
transmissions.
When multiple ID numbers are used, the ArgosTransmit() function works best.
When ArgosTransmit() is executed, the contents of the specified data buffer are
transmitted once. ArgosTransmit() gives full control of timing of
transmissions to the datalogger programmer. Special care must be taken to
avoid transmitting too often. The programmed repetition period must match
the System Use Agreement between the user and Service Argos.
2.5 ArgosError (Error as string)
Public ErrorCodes as string * 20
ArgosError(ErrorCodes)
2.5.1 ErrorCodes
ErrorCodes is a string variable. ArgosError sends the command &h09, and
then waits for the returned string plus the ACK or NAK character. The
returned string is stored in the string variable ErrorCodes. If NAK (&h15) is
returned, then ArgosError() did not receive a proper response from the ST-20.
3. ST-20 Installation
3.1 BNC Antenna Connector and Antenna
The RF output is 50 ohm impedance at a nominal 1 watt output at about 401.6
MHz. Frequency is dependent on setup. The antenna cable should be kept
reasonably short, and connections kept dry. The default antenna is an omni
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