ST-21 Argos Satellite Transmitter Revision: 9/12 C o p y r i g h t © 2 0 0 6 - 2 0 1 2 C a m p b e l l S c i e n t i f i c , I n c .
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Table of Contents PDF viewers: These page numbers refer to the printed version of this document. Use the PDF reader bookmarks tab for links to specific sections. 1. Overview......................................................................1 1.1 1.2 1.3 1.4 1.5 Specifications .......................................................................................1 Serial Port.............................................................................................1 Data Buffers ......................
Table of Contents Figures 1-1. 1-2. 3-2. ST-21 Argos Satellite Transmitter....................................................... 1 The ST-21’s 9-pin connector attaches to the datalogger via the SC12 cable ....................................................................................... 2 The ST-21’s BNC connector attaches to the antenna via the antenna cable.................................................................................... 6 The 12022 antenna .....................................
ST-21 Argos Satellite Transmitter 1. Overview The ST-21 is a certified Argos PTT satellite transmitter for use with Campbell Scientific CRBasic dataloggers. Service Argos data transceivers fly aboard two NOAA polar orbiting satellites. With an orbit altitude close to 800 kilometers, the satellites are at a relatively low orbit. The low orbit allows for low transmit power, low battery power requirements and the use of an omnidirectional antenna.
ST-21 Argos Satellite Transmitter TABLE 1-1. ST-21 Serial Port Configuration Pin number 1 2 3 4 5 6 7 8 9 Function +5 volts Ground NC TXD (data out) NC SDE (input) CLK/HS (input) +12 volts RXD (data in) FIGURE 1-2. The ST-21’s 9-pin connector attaches to the datalogger via the SC12 cable 1.3 Data Buffers The ST-21 has 8 internal data buffers. Before a data buffer can be used, a valid Argos ID number, repetition rate and frequency must be assigned to the buffer.
ST-21 Argos Satellite Transmitter taken to avoid transmitting too often. The programmed repetition period must match the System Use Agreement between the user and Service Argos. 1.5 One Argos ID Number The ArgosDataRepeat() function is most useful when only one Argos ID number is used. It does not matter how many data buffers use the same ID. ArgosDataRepeat() allows the selection of which data buffers will be transmitted, and at what repetition period.
ST-21 Argos Satellite Transmitter 2.2 ArgosData ArgosData (ResultCode, ST21Buffer, DataTable, NumRecords, DataFormat) 2.2.1 General Description The ArgosData instruction is used to load data to one of the 7 available data buffers. The data buffers are numbered 0 through 7, with number 7 being reserved for the ST-21 internal temperature. When ArgosData is executed, any data already in the associated buffer is erased before new data is loaded.
ST-21 Argos Satellite Transmitter 2.3 ArgosDataRepeat Usage: Dim BufferNumber(8) as Boolean ArgosDataRepeat(Result Code, Repetition Rate, Number Repeats, BufferNumber()) 2.3.1 Result Code The Result Code is a numeric variable that is set true (-1) when the ArgosDataRepeat instruction is successful. 2.3.2 Repetition Rate The Repetition Rate will set the time between each repetition. A negative number will cause the default repetition rate to be used.
ST-21 Argos Satellite Transmitter 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.
ST-21 Argos Satellite Transmitter FIGURE 3-2. The 12022 antenna 3.2 Environmental Enclosure The ST-21 is designed to work in a dry, non-condensing environment. A proper enclosure should be used to keep water, dust and other environmental contaminates away from the ST-21. Always use desiccant inside the enclosure to keep trapped moisture from condensing on the electronics. 4.
ST-21 Argos Satellite Transmitter successful data transmissions per satellite pass will increase with a decrease in the repetition rate. More detailed information regarding Service Argos and satellite coverage is available from Service Argos. On the Web, see http://www.argosinc.com/. The Service Argos North American office can be contacted by email at useroffice@argosinc.com or phone (301) 925-4411. http://www.cls.fr/html/argos/welcome_en.html 5.
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