Campbell Scientific ST-20 User Manual

ST-20 Argos Satellite

Transmitter

Picture of ST-20

Revision: 6/07

Copyright © 2006-2007

Campbell Scientific, Inc.

Warranty and Assistance

The ST-20 ARGOS SATELLITE TRANSMITTER is warranted by
CAMPBELL SCIENTIFIC, INC. to be free from defects in materials and
workmanship under normal use and service for twelve (12) months from date
of shipment unless specified otherwise. Batteries have no warranty.
CAMPBELL SCIENTIFIC, INC.'s obligation under this warranty is limited to
repairing or replacing (at CAMPBELL SCIENTIFIC, INC.'s option) defective
products. The customer shall assume all costs of removing, reinstalling, and
shipping defective products to CAMPBELL SCIENTIFIC, INC. CAMPBELL
SCIENTIFIC, INC. will return such products by surface carrier prepaid. This
warranty shall not apply to any CAMPBELL SCIENTIFIC, INC. products
which have been subjected to modification, misuse, neglect, accidents of
nature, or shipping damage. This warranty is in lieu of all other warranties,
expressed or implied, including warranties of merchantability or fitness for a
particular purpose. CAMPBELL SCIENTIFIC, INC. is not liable for special,
indirect, incidental, or consequential damages.

Products may not be returned without prior authorization. The following
contact information is for US and International customers residing in countries
served by Campbell Scientific, Inc. directly. Affiliate companies handle
repairs for customers within their territories. Please visit
www.campbellsci.com to determine which Campbell Scientific company
serves your country. To obtain a Returned Materials Authorization (RMA),
contact CAMPBELL SCIENTIFIC, INC., phone [phone]. After an
applications engineer determines the nature of the problem, an RMA number
will be issued. Please write this number clearly on the outside of the shipping
container. CAMPBELL SCIENTIFIC's shipping address is:

CAMPBELL SCIENTIFIC, INC.

RMA#_____
815 West 1800 North
Logan, Utah 84321-1784

CAMPBELL SCIENTIFIC, INC. does not accept collect calls.

ST-20 Table of Contents

PDF viewers note: These page numbers refer to the printed version of this document. Use
the Adobe Acrobat® bookmarks tab for links to specific sections.

1. Overview.......................................................................1

1.1 Specifications............................................................................................1

1.2 Serial Port.................................................................................................1

1.3 Data Buffers..............................................................................................3

1.4 Multiple Argos ID Numbers.....................................................................3

1.5 One Argos ID Number .............................................................................3

2. Datalogger Programming............................................3

2.1 Argos Setup ..............................................................................................3

2.1.1 Result Code.....................................................................................4

2.1.2 Buffer Number................................................................................4

2.1.4 Frequency........................................................................................4

2.2 ArgosData.................................................................................................4

2.2.1 General Description........................................................................4

2.2.2 ResultCode......................................................................................4

2.2.3 ST20Buffer .....................................................................................4

2.2.4 DataTable........................................................................................4

2.2.5 NumRecords ...................................................................................5

2.2.6 DataFormat .....................................................................................5

2.3 ArgosDataRepeat......................................................................................5

2.3.1 Result Code.....................................................................................5

2.3.2 Repetition Rate................................................................................5

2.3.3 Number Repeats..............................................................................5

2.3.4 Buffer Number................................................................................5

2.4 ArgosTransmit..........................................................................................6

2.4.1 Result Code.....................................................................................6

2.4.2 Buffer Number................................................................................6

2.5 ArgosError (Error as string) .....................................................................6

2.5.1 ErrorCodes......................................................................................6

3. ST-20 Installation.........................................................6

3.1 BNC Antenna Connector and Antenna.....................................................6

3.2 Environmental Enclosure..........................................................................7

4. Satellite Orbit Patterns................................................7

5. Antenna Placement .....................................................7

i

ST-20 Table of Contents

Figures

Table

1-1. ST-20 Argos Satellite Transmitter.......................................................... 1

1-2. ST-20 with CR1000 Datalogger in Enclosure........................................ 2

1-1. ST-20 Serial Port Configuration............................................................. 2

ii

ST-20 Argos Satellite Transmitter

1. Overview

The ST-20 is a certified Argos PTT satellite transmitter for use with Campbell
Scientific, Inc. 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. The orbit period is approximately 1 hour and 45 minutes,
which allows hourly data at extreme northern and southern latitudes. Near the
equator there are about six satellite passes per day that are not evenly spaced.
During the average satellite pass, the satellite is in view for about 10 minutes.

1.1 Specifications

Power supply: Nominal 12 volts DC, 10 volts DC minimum,

Current drain at
12 volts:

Data Buffers: 7 buffers, 32 byte each. Note: 28 bit ID numbers reduce

Dimensions: 7.5 L x 2.25 H x 1.25 W inches, 19 L x 6 H x 3 W cm.
Weight: 7.9 oz, 224 gm

1.2 Serial Port

The ST-20 is specifically designed to work with Campbell Scientific, Inc.
CRBasic dataloggers. The ST-20 serial port is connected to the CS I/O port of
the datalogger. The datalogger provides 12 volt DC po wer and gr o un d thr ou g h
pins 8 and 2 respectively. Communications utilize the Campbell Scientific,
Inc. Synchronous Device for Communications (SDC) protocol, which allows
several devices to be connected to the CS I/O port at the same time. Each
device is addressed or pin enabled; the ST-20 is address 4.

FIGURE 1-1. ST-20 Argos Satellite Transmitter

16 volts DC maximum

1.12 mA quiescent, 375 mA during transmit

buffers to 31 bytes.

1

ST-20 Argos Satellite Transmitter

TABLE 1-1. ST-20 Serial Port Configuration

Pin number Function

1 +5 volts
2 Ground
3 NC
4 TXD (data out)
5 NC
6 SDE (input)
7 CLK/HS (input)
8 +12 volts
9 RXD (data in)

2

FIGURE 1-2. ST-20 with CR1000 Datalogger in Enclosure

1.3 Data Buffers

The ST-20 has 8 internal data buffers. Before a data buffer can be used, a val i d
Argos ID number, repetition rate and frequency must be assigned to the buffer.
The Argos ID numbers must be entered as a decimal and a Hexadecimal
number. The ST-20 uses the Hexadecimal format to determine if the ID is a 28
bit ID number. When using 28 bit ID numbers, 31 byt e s of data can be stored
in the buffer. When using 20 bit ID numbers, 32 bytes of data can be stored in
the buffer. The data buffers are numbered 0 through 7, with 7 being reserved
for other uses.

Data buffer setup can be done by the factory or under datalogger control. The
factory settings are stored in non-volatile memory. Settings that have been
changed by the datalogger are erased when the ST-20 resets.

1.4 Multiple Argos ID Numbers

The use of multiple ID numbers can significantly change how the datalogger is
programmed. 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.

ST-20 Argos Satellite Transmitter

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. When ArgosDataRepeat() is used to
start data transmission, the ST-20 will wait one repetition period between each
transmission. One buffer is transmitted each transmission, regardless of how
many buffers have been enabled. The maximum number of transmissions that
can be scheduled with ArgosDataRepeat() is 255.

2. Datalogger Programming

There are 5 programming instructions available for use with the ST-20 Argos
PTT: ArgosSetup, ArgosData, ArgosDataRepeat, ArgosTra nsmit, and
ArgosError. The use of ArgosSetup is optional. ArgosData and
ArgosDataRepeat are used to enable transmission of data. More advanced
applications can use ArgosTransmit. If the setup parameters of the PTT need
to be changed, use ArgosSetup first. The setups are maintained in memory
until the PTT resets. Once the setup parameters are set, use ArgosData
followed by ArgosAutoRepeat. Data in a buffer is saved until the PTT resets
or is overwritten by another occurrence of ArgosData. If either the
ArgosDataRepeat or ArgosTransmit instruction tries to use a data buffer that
has not been setup, the instruction will fail.

2.1 Argos Setup

ArgosSetup (Result Code, Buffer Number, Decimal ID, Hexadecimal ID,
Frequency)

3

ST-20 Argos Satellite Transmitter

2.1.1 Result Code

Result Code used to determine if command executed successfully. The Result
Code is set true on success, and false on failure.

2.1.2 Buffer Number

Buffer Number is the ST-20 buffer to setup. Valid entries are 0 through 6.

2.1.3 Decimal ID Number

The Decimal ID number, and Hexadecimal ID are assigned to the Buffer
Number. Entries must be valid ID numbers or ArgosSetup will return False.
The decimal ID is not a different representation of the same number as the
Hexadecimal ID. The two ID numbers are different.

2.1.4 Frequency

Frequency to be assigned to the Buffer Number. Frequency is in Hertz. Valid
entries: 401630000 to 401656000 in steps of 2000 Hz and 4016 76000,
401678000, and 401680000 Hz.

2.2 ArgosData

ArgosData (ResultCode, ST20Buffer, 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-20 internal temperature. When ArgosDa ta is executed, any
data already in the associated buffer is erased before new data is loaded. If the
Argos ID number associated with the buffer is a 20 bit ID number, up to 32
bytes of data can be loaded. If the associated ID number is a 28 bit ID, then
only 31 bytes can be loaded. Extra bytes are discarded. The ArgosData
instruction does not enable data transmission. To enable data transmission, the
ArgosDataRepeat, or ArgosTransmit instruction must be used.

2.2.2 ResultCode

The Result Code is a numeric variable used to store the result of the ArgosData
instruction. If the result code is true (-1), ArgosData executed successfully.

2.2.3 ST20Buffer

The ST20Buffer is the number of the buffer where data sho uld be loade d .
Valid buffer numbers are 0 through 6.

4

2.2.4 DataTable

DataTable is the name of the data table where data records will be read from.

2.2.5 NumRecords

2.2.6 DataFormat

ST-20 Argos Satellite Transmitter

NumRecords is the number of data records that will be copied from the data
table to the Argos PTT. Care should be taken to make sure the total amount of
data does not exceed what the buffer can hold, 32 bytes for a 20 bit ID number
and 31 bytes for a 28 bit ID number. See DataFormat (section 2.2.6) for details
on regarding memory usage.

There are two data formats. Enter “FP2” to use the Campbell Scientific two
byte, floating decimal point format. To use FP2, the data table (section 2.2.4)
must store data as type FP2. Each data value will use two bytes of memory.
Enter “nnn.nnn.nnn…” to use the integer format, where nnn is an integer that
specifies the total number of bits to be used for each data value. As an
example: “5,8,16,8,3” would use 5 bytes or 40 bits fo r five data values. The
first data value would have 5 bits of resolut i on, the n 8 f or t he next, then 16 for
the third and so forth. With the integer format, data must be stored in the data
table as type Long.

When using integer format with bits/data point designator, each data point in
the data record needs to be accounted for in the DataFormat field, or the
datalogger will assume 2 bytes (16 bits) for each unaccounted for data point.

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. Using a value between
0 and 255 will set the repetition rate to the new value plus 42 seconds. The
ST-20 adds 42 seconds to the repeat rate with the maximum being 297.

2.3.3 Number Repeats

Number Repeats is how many times the transmission will be repeated. Valid 0
to 255.

2.3.4 Buffer Number

BufferNumber() is an eight element array of Boolean. Each elem ent of
BufferNumber corresponds to the same buffer number -1 in the ST-20. Set the
corresponding element to true to use a buffer, or false to not use the buffer.
Data can be in a buffer that is set to false.

5

ST-20 Argos Satellite Transmitter

The ArgosDataRepeat instruction is most useful when only usin g 1 ID nu mber
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

6

directional and unity gain. The antenna should be mounted vertically. An
antenna with gain will perform significantly worse then an antenna with unity
gain.

3.2 Environmental Enclosure

The ST-20 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-20. Always use desiccant inside the enclosure
to keep trapped moisture from condensing on the electronics.

4. Satellite Orbit Patterns

At least two NOAA Polar Orbiting Environmental Satellites (POES) carry the
Argos transceivers and are operational at any given time. The orbits carry the
satellites over the North and South poles of the Earth in a sun synchronous
pattern. Orbit period is close to 102 minutes. The satellite foot print is about
5000 km in diameter. At latitudes greater than 75 degrees, each satellite
provides coverage each pass. Each satellite passes over the poles 14 times a
day providing 28 satellite passes per day. Coverage decreases with latitude.
At the equator the PTT will “see” a satellite six or seven times a day. The
duration of the POES satellite visibility depends on the angle from the PTT to
the satellite. If the satellite passes directly overhead, the satellite will be visible
for about 15 minutes. If the satellite passes close to the horizon, as viewed
from the PTT, the satellite will only be visible for a short time. On average,
each satellite pass is visible for about ten minutes. If using a 200 second
repetition rate, a satellite pass could result in three received messages from the
PTT.

ST-20 Argos Satellite Transmitter

Satellite coverage must be considered when planning data collection and
transmission. Given the variability of satellite coverage, hourly data cannot be
expected unless the PTT is located above 75 degrees latitude. The number of
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
[e-mail] or phone [phone].

http://www.cls.fr/html/argos/welcome_en.html

5. Antenna Placement

The position of polar orbiting satellites relative to the PTT will change during
the satellite pass and with each satellite pass. The antenna must broadcast
evenly to all areas of the sky. The antenna is omnidirectional. Mount the
antenna vertically. Choose a location with a clear view of the sky in all
directions. Any obstruction between the PTT antenna and the sky can block
data transmission between the satellite and the PTT.

7

ST-20 Argos Satellite Transmitter

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Campbell Scientific Companies

Campbell Scientific, Inc. (CSI)

815 West 1800 North

Logan, Utah 84321

UNITED STATES
www.campbellsci.com
[e-mail]

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PO Box 2450

Somerset West 7129

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[e-mail]

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PO Box 444

Thuringowa Central
QLD 4812 AUSTRALIA
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CEP: 005543-000 São Paulo SP BRAZIL

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[e-mail]

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11564 - 149th Street NW

Edmonton, Alberta T5M 1W7

CANADA

www.campbellsci.ca

[e-mail]

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Campbell Park

80 Hathern Road

Shepshed, Loughborough LE12 9GX

UNITED KINGDOM

www.campbellsci.co.uk

[e-mail]

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08013 Barcelona

SPAIN
www.campbellsci.es
[e-mail]

Please visit www.campbellsci.com to obtain contact information for your local US or International representative.