Vaisala GA31 User manual

USER'S GUIDE
Vaisala GPS Antenna
GA31
M210546EN-C

PUBLISHED BY
Vaisala Oyj Phone (int.): [phone]
P.O. Box 26 Fax: [phone]
FIN-00421 Helsinki
Finland
Visit our Internet pages at http://www.vaisala.com/
© Vaisala 2008
No part of this manual may be reproduced in any form or by any means, electronic or
mechanical (including photocopying), nor may its contents be communicated to a third
party without prior written permission of the copyright holder.
The contents are subject to change without prior notice.
Please observe that this manual does not create any legally binding obligations for
Vaisala towards the customer or end user. All legally binding commitments and
agreements are included exclusively in the applicable supply contract or Conditions of
Sale.

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Table of Contents
CHAPTER 1
GENERAL INFORMATION............................................................................ 3
About This Manual ................................................................... 3
Contents of This Manual ....................................................... 3
Safety......................................................................................... 4
ESD Protection...................................................................... 4
Trademarks ............................................................................... 5
License Agreement .................................................................. 5
Warranty.................................................................................... 5
Getting Help .............................................................................. 5
CHAPTER 2
PRODUCT OVERVIEW.................................................................................. 7
General ...................................................................................... 7
Construction ............................................................................. 7
CHAPTER 3
INSTALLATION.............................................................................................. 9
Selecting Installation Site........................................................ 9
Installation .............................................................................. 10
CHAPTER 4
OPERATION AND MAINTENANCE............................................................ 11
Operation ................................................................................ 11
Preventive Maintenance ........................................................ 11
CHAPTER 5
SPECIFICATIONS........................................................................................ 13
General Specifications........................................................... 13
CHAPTER 6
PARTS LIST ................................................................................................. 15
APPENDIX A
INSTALLATION DRAWINGS ...................................................................... 17
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Chapter 1 ______________________________________________________ General Information
CHAPTER 1
GENERAL INFORMATION
This chapter provides general notes for the manual and the product.
About This Manual
This manual provides the information needed to use the Vaisala GPS
Antenna GA31.
Contents of This Manual
This manual consists of the following chapters:
- Chapter 1, General Information, provides important safety, revision
history, and warranty information for the product.
- Chapter 2, Product Overview, yields a general description of the
system.
- Chapter 3, Installation, provides information on GA31 installation
and on the selection of a suitable site for the antenna.
- Chapter 4, Operation and Maintenance, explains about the use of
the antenna and about preventive maintenance.
- Chapter 5, Specifications, yields the technical specifications for the
antenna system.
- Chapter 6, Parts List, gives detailed information on antenna
structure.
- Appendix A, Installation Drawings, contains the installation
drawing DRW2288818 for GA31.
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Safety
Throughout the manual, important safety considerations are
highlighted as follows:
WARNING Warning alerts you to a serious hazard. If you do not read and follow
instructions very carefully at this point, there is a risk of injury or
even death.
CAUTION Caution warns you of a potential hazard. If you do not read and
follow instructions carefully at this point, the product could be
damaged or important data could be lost.
NOTE Note highlights important information on using the product.
ESD Protection
Electrostatic Discharge (ESD) can cause immediate or latent damage
to electronic circuits. Vaisala products are adequately protected
against ESD for their intended use. However, it is possible to damage
the product by delivering electrostatic discharges when touching,
removing, or inserting any objects inside the equipment housing.
To make sure you are not delivering high static voltages yourself:
- Handle ESD sensitive components on a properly grounded and
protected ESD workbench. When this is not possible, ground
yourself to the equipment chassis before touching the boards.
Ground yourself with a wrist strap and a resistive connection cord.
When neither of the above is possible, touch a conductive part of
the equipment chassis with your other hand before touching the
boards.
- Always hold the boards by the edges and avoid touching the
component contacts.
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Chapter 1 ______________________________________________________ General Information
Trademarks
Microsoft®, Windows®, and Windows NT®are registered
trademarks of Microsoft Corporation in the United States and/or other
countries.
License Agreement
All rights to any software are held by Vaisala or third parties. The
customer is allowed to use the software only to the extent that is
provided by the applicable supply contract or Software License
Agreement.
Warranty
For certain products Vaisala normally gives a limited one year
warranty. Please observe that any such warranty may not be valid in
case of damage due to normal wear and tear, exceptional operating
conditions, negligent handling or installation, or unauthorized
modifications. Please see the applicable supply contract or conditions
of sale for details of the warranty for each product.
Getting Help
For technical questions or for comments on the manuals, contact the
Vaisala technical support:
E-mail [email protected]
Telephone [phone]
Fax [phone]
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Chapter 2 ________________________________________________________ Product Overview
CHAPTER 2
PRODUCT OVERVIEW
This chapter provides a general description of the Vaisala GPS
Antenna GA31.
General
The Vaisala GPS Antenna GA31 is intended for reception of C/A
code signals from the NAVSTAR satellites. These signals are Right
Hand Circular Polarization (RHCP) centered at 1575.42 MHz. The
GA31 is suitable for stations equipped with the GPS wind finding
system.
The Radiator Element with the Low Noise Amplifier module is a
commercially available GPS antenna unit, that rejects the unwanted
Left Hand Circular Polarisation (LHCP) and out-of-band signals. The
antenna filters, amplifies and transfers the signals to the navigation
unit for further processing.
The GA31 differs from GA20, another GPS antenna version, in that it
includes an N-to-TNC cable for connecting the antenna to sounding
instruments.
Construction
The active GPS Antenna module consists of an L1 frequency antenna
element integrated with an internal interference rejection filter and
Low Noise Amplifier (LNA). The element is enclosed within a
radome with an attached mounting base. A single N connector carries
both the GPS signal to the navigation unit and the 5-voltage power to
the LNA. The radiator element and preamplifier are housed in a
watertight round-shaped plastic radome that is mounted on top of the
1.5-meter pole.
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The threaded stainless-steel insert in the base of the antenna accepts a
standard 1"-14 pole mount. The N connector is located inside the
threaded insert allowing the antenna cable to be routed through the
pole mount, which protects the cable connection from the environment
for added reliability.
The antenna is equipped with a mounting flange at the lower end of
the pole.
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Chapter 3 _____________________________________________________________ Installation
CHAPTER 3
INSTALLATION
This chapter provides information on GA31 installation and on the
selection of a suitable site for the antenna.
Selecting Installation Site
Proper siting of the antenna is important for good performance. As a
general rule, the antenna should be installed so that it is not screened
by large obstacles, such as buildings, thick forest, or high masts of
metal.
For best reception, choose an antenna location that has a clear view of
the sky down to the horizon in all directions. This will ensure that all
satellites in view can be tracked without obstruction. In some cases it
may be required to mount the antenna on an elevated structure to
guarantee unobstructed reception.
A single obstacle has little effect on reception if it is not exceptionally
dense or very near the antenna (less than 20 meters). Sparse forest
causes some attenuation but is usually no hindrance.
Antenna masts and other similar metal structures with a small
diameter do not normally disturb reception to a serious extent if they
are located more than 20 meters away. Metal roofs and other
corresponding large surfaces can reflect signals in some instances,
causing multipath reception. A large metal structure or a building
screens the antenna, and reception through it is then impossible.
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Installation
CAUTION There is protective grease on the antenna connector that must not be
removed. However, be careful not to let sand or dirt get to the
connector during installation.
The antenna can be mounted with the mounting flange on a
foundation that is solid enough.
Alternatively, the flange can be removed and the pole can be attached
with the clamps included in the delivery, for instance, to a vertical rail
of a railing. (For more information on these installation options, see
Drawing GA45008).
Before attaching the antenna pole to the antenna unit, it is
recommended to pass the cable through the pole by doing the
following:
1. To make it easier to slip the cable to the tube, first remove the
bushing on the top of the pole.
2. Loosen two M4 screws and lift the bushing up.
3. Pass the cable through the pole.
4. Before attaching the cable to the antenna unit, pass the cable
through the bushing, too.
5. After attaching the connector, wring the bushing to the thread of
the antenna unit and press the bushing to the top of the tube,
pulling the cable cautiously out from the tube at the same time.
6. Lock the knob with M4 screws.
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Chapter 4 ________________________________________________ Operation and Maintenance
CHAPTER 4
OPERATION AND MAINTENANCE
This chapter explains about the use of the GA31 antenna and about
preventive maintenance.
Operation
The GA31 can be used in conjunction with Vaisala sounding
instruments equipped with MWG processor boards.
Sensitive parts of the antenna are protected by the plastic cover and
are thus not prone to mechanical damage.
Preventive Maintenance
The cover also protects the parts from rain. Nevertheless, from time to
time it is advisable to inspect the antenna for possible corrosion
damage and ensure that the connectors are in good condition.
When disassembling the antenna element, the M4 screws are loosened
first. The antenna element with the mounting bush can then be
removed.
If the antenna operates poorly as a whole, first check that the DC
supply input (+5V) is found at the end of the antenna cable. If the
supply voltage is in order, the fault is possibly in the antenna
preamplifier. Replace the antenna element GA45007.
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Chapter 5 ___________________________________________________________ Specifications
CHAPTER 5
SPECIFICATIONS
This chapter yields the technical specifications for the GPS antenna.
General Specifications
Table 1 General Specifications
Feature Specification
Operating temperature -40°C to +85°C
Storage temperature -55°C to +100°C
LNA power +5V DC (±10%)
Power consumption 22 mA (nominal)
Frequency 1575 MHz
Output impedance 50 Ω
VSWR 2:1
Gain 35 dB (nominal)
Noise figure 2.7 dB (nominal)
Pass-band width 50 MHz
Azimuth coverage 360°(omni-directional)
Elevation coverage 0°to 90°elevation (hemispherical)
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Chapter 6 ______________________________________________________________ Parts List
CHAPTER 6
PARTS LIST
Parts list for GA31 Antenna is shown in the following table.
Table 2 Parts List for GA31 Antenna
Ref. Part no. Item Manuf./Supplier
GA45007 Antenna Element, with N Connector
GA35002 Pedestal Assembly
60172 Stud Bolt
GA35009 Base of Antenna
GA45003 Antenna Tube
GA45004 Mounting Bush of Antenna
0952 Anchor M10 L=40
DRW216768 Coaxial Cable TNC(m)/N(m), RG213,
33 m
0567 Wire Tie, SSTL 1371933/72.94.370 A-COM Oy
18436 Clamp, D58-75mm, stainless AISI
316, AWAB 1495220, 2pcs
Etola
4185 Allen Key, AV 3.0/Zn, DIN911 Wurth/Ruuvitalo Oy
16267 Washer A10.5
3069 Hex Nut M10
3822 Screw M6*8
4337 Spring Washer B4
4342 Spring Washer B10
4453 Slot Screw M4*12
x) CA3224 Pedestal Assembly
x) 0919CA Guying Wire Set
x) 4488 Screw M10x40
x) 60172 Screw M10x150
x) 16267 Washer A 10
x) 4342 Spring Washer B 10
x) 3069 Hex Nut M10
x) 0952 Anchor M10 L=40
x) = for optional pedestal
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Appendix A ____________________________________________________ Installation Drawings
APPENDIX A
INSTALLATION DRAWINGS
This chapter contains the installation drawing DRW2288818 for
GA31.
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