Vaisala RB31 User manual

Vaisala Telemetry Antenna
RB31
USER'S GUIDE
M210538EN-C
February 2006

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 2006
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
General Safety Considerations ............................................. 4
Feedback............................................................................... 4
Product Related Safety Precautions ...................................... 5
ESD Protection ......................................................................... 5
Recycling .................................................................................. 6
Warranty.................................................................................... 6
Technical Support.................................................................... 6
CHAPTER 2
PRODUCT OVERVIEW.................................................................................. 7
Introduction to RB31................................................................ 7
Construction ............................................................................. 8
Antenna Segments................................................................ 8
Antenna Amplifier and Switch RBD121 ................................ 9
CHAPTER 3
INSTALLATION............................................................................................ 11
Installation Site....................................................................... 11
Unpacking ............................................................................... 11
Antenna Base Installation ..................................................... 12
Assembling the Antenna ....................................................... 12
CHAPTER 4
OPERATION................................................................................................. 13
General .................................................................................... 13
Operation Modes.................................................................... 13
Options.................................................................................... 14
Long Antenna Cables.......................................................... 14
CHAPTER 5
MAINTENANCE ........................................................................................... 15
Avoiding Corrosion................................................................ 15
Disassembling the Antenna .................................................. 15
Basic Troubleshooting .......................................................... 16
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CHAPTER 6
TECHNICAL DATA ......................................................................................17
CHAPTER 7
PARTS LIST .................................................................................................19
CHAPTER 8
DRAWINGS ..................................................................................................23
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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 information for installing, operating, and
maintaining Vaisala Telemetry Antenna RB31.
Contents of This Manual
This manual consists of the following chapters:
- Chapter 1, General Information, provides general notes for the
manual and the product.
- Chapter 2, Product Overview, gives a general description of the
RB31 system.
- Chapter 3, Installation, explains about unpacking and setting up the
antenna.
- Chapter 4, Operation, provides additional information for the users
of the RB31 system.
- Chapter 5, Maintenance, provides information on servicing
operations.
- Chapter 6, Technical Data, provides the technical specifications.
- Chapter 7, Parts List, contains the parts list for Vaisala Telemetry
Antenna RB31.
- Chapter 8, Drawings, contains the essential drawings for Telemetry
Antenna RB31.
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General Safety Considerations
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.
Feedback
Vaisala Customer Documentation Team welcomes your comments
and suggestions on the quality and usefulness of this publication. If
you find errors or have other suggestions for improvement, please
indicate the chapter, section, and page number. You can send
comments to us by e-mail: [email protected]
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Chapter 1 ________________________________________________________ General Information
Product Related Safety Precautions
The Vaisala Telemetry Antenna RB31 delivered to you has been
tested for safety and approved as shipped from the factory. Note the
following precautions:
WARNING Ground the product, and verify outdoor installation grounding
periodically to minimize shock hazard.
CAUTION Do not modify the unit. Improper modification can damage the
product or lead to malfunction.
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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Recycling
Recycle all applicable material.
Dispose of batteries and the unit according to statutory regulations.
Do not dispose of with regular household refuse.
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.
Technical Support
For technical questions, contact the Vaisala technical support:
E-mail [email protected]
Fax [phone]
If the product needs repair, please follow the instructions below to
speed up the process and to avoid extra costs to you.
1. Read the warranty information.
2. Contact Vaisala technical support via e-mail or fax and request
for RMA (Return Material Authorization) and shipping
instructions.
3. Proceed as instructed by Vaisala technical support.
NOTE RMA must always be requested from Vaisala technical support
before returning any faulty material.
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Chapter 2 __________________________________________________________ Product Overview
CHAPTER 2
PRODUCT OVERVIEW
This chapter gives a general description of the RB31 system.
Introduction to RB31
Vaisala Telemetry Antenna RB31 is a directional UHF antenna used
with the Vaisala DigiCORA® Sounding System to receive radiosonde
signals in the 400 MHz meteorological band.
RB31 can be used in conjunction with the Vaisala DigiCORA®
equipped with Vaisala Sounding Processing Subsystem SPS311.
The main idea when planning the antenna arrangement was to obtain a
radiation pattern providing a good signal during sounding under any
wind conditions.
RB31 is well-suited for use in fixed installations. The antenna has no
moving parts; the radiation pattern of the antenna can be electrically
directed to track the flying radiosonde.
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Construction
Vaisala Telemetry Antenna RB31 consists of the directional antenna
segments, Antenna Amplifier and Switch RBD121, radome, antenna
base, and antenna cable.
Antenna Segments
The antenna consists of six antenna segments for horizontal reception
and one segment for upwards direction.
Each horizontal segment is a folded ground plane antenna with a 60°
corner reflector. This type of antenna provides a favorable front-to-
back ratio and directivity. Maximum gain direction is towards the
horizon, where the distance between the radiosonde and the receiver is
at its greatest and the field intensity at its weakest. The gain of an
antenna element, at 0° elevation angle, is 12 dB (over 1/2 wave
antenna).
For the upwards direction - or high elevation angles - the antenna is
equipped with a cross dipole. The cross dipole has radiators bent down
to enable the antenna to receive transmissions having extensive
polarization fluctuation.
One antenna segment at a time is connected for the reception. The
antenna switch is controlled to make the selection between seven
directions: North (N), North-East (NE), South-East (SE), South (S),
South-West (SW), North-West (NW) and Upwards (90°).
Cross dipole
Reflector
plate
Switching unit
Radiation element
0211-101
Figure 1 Antenna Elements
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Chapter 2 __________________________________________________________ Product Overview
Antenna Amplifier and Switch
RBD121
Cables from the antenna elements connect to coaxial connectors at the
Antenna Amplifier and Switch RBD121.
The antenna amplifier and switch has eight coaxial connectors. They
are marked with OUT (antenna signal output), NW (North-West), N
(North), NE (North-East), SE (South-East), S (South), SW ( South-
West) and 90° (upwards).
The OUT connector is connected to the cable from output terminal of
RB31 on the through-hole plate. The other terminals are connected to
the antenna radiators: 90° to the cross dipole and the others to the
corner radiator of the marked direction
Figure 2 shows the cabling scheme of an RBD121 unit.
0312-117
Figure 2 Cabling Principle of RDB121 Unit
For more detailed information on the RBD121 refer to “Antenna
Amplifier and Switch RBD121 Technical Reference”.
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Chapter 3 _______________________________________________________________ Installation
CHAPTER 3
INSTALLATION
This chapter explains about unpacking and setting up the antenna.
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.
A single obstacle has little effect on reception provided that it is not
exceptionally dense or very near (less than 20 meters) the antenna.
Sparse forest causes some attenuation but is usually no hindrance.
Antenna masts and other similar metal structures of a small diameter
do not normally disturb reception to a serious extent if more than 20
meters away. Metal roofs and other corresponding large surfaces can
reflect signals in some instances, causing fading of short duration. A
large metal structure or a building screens the antenna, and reception
through it is then impossible.
Unpacking
The Antenna is delivered as a single functional unit including the
radome and the internal parts (antenna elements, antenna amplifier
and switch) with all connections completed. Therefore, unpacking is a
simple operation and requires no special instructions.
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Antenna Base Installation
For antenna base installation, refer to assembly drawing DRW214844
at the end of this manual.
Assembling the Antenna
The antenna is installed with the "N" side pointing to the north.
The antenna cable is connected to the corresponding connector at the
antenna base. The green-yellow ground cable is connected to the
nearest grounding point. On shipboard installations this is the antenna
support pipe.
On roof mounting or terrain installations, the ground cable can be
extended if necessary for connection to a proper ground point, for
example to a water conduit or heating pipe, a metal structure or other
comparable object.
For connecting the antenna as a part of the sounding system see
DigiCORA® Installation Manual.
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Chapter 4 ________________________________________________________________ Operation
CHAPTER 4
OPERATION
This chapter provides additional information for the users of the RB31
system.
General
Vaisala Telemetry Antenna RB31 can be used in conjunction with the
Vaisala DigiCORA® equipped with Vaisala Sounding Processing
Subsystem SPS311.
Operation Modes
The antenna consists of six segments, of which one at a time is
connected to for the reception. Selection is made between seven
directions: North (N), North-East (NE), South-East (SE), South (S),
South-West (SW), North-West (NW) and Upwards (90°).
Antenna segment is selectable either automatically or manually. Refer
to the DigiCORA® User's Guide for details on manual and automatic
operation modes.
In automatic mode the antenna element giving the highest signal
strength is connected for reception. The selection of the antenna
element does not disturb the sounding.
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Options
Long Antenna Cables
The standard length of the antenna cable is 30 meters and the
attenuation of the standard cable type (RG-213/U) is 14 dB/100 m at
400 MHz.
Other cable types and lengths are possible, but for full system
performance the attenuation of the antenna cable should be less than
10 dB. With different cable types this leads to the following
approximate maximum cable lengths:
Table 1 Approximate Maximum Cable Lengths
Cable Type Vaisala Part No. Cable Length (m)
Standard cable (RG213/U) 3969 75
Andrew LDF4-50A - 200
Suhner RG213/U-5 - 90
Nokia AJS 50-3 (RG58C/U) 3053 27
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Chapter 5 ______________________________________________________________ Maintenance
CHAPTER 5
MAINTENANCE
This chapter provides information on servicing operations.
Avoiding Corrosion
Sensitive parts of the antenna are protected by the plastic dome and
are thus not prone to mechanical damage. The cover also protects the
parts from rain and openings at its base allow condensed water to drip
off. Nevertheless, from time to time it is advisable to inspect for
possible corrosion damage and ensure that the connectors are in good
condition.
Disassembling the Antenna
When disassembling the antenna, the rim bolts are loosened first. (See
drawing at the end of this manual). The cover can then be removed.
The antenna elements and the cross dipole are accessible. If any of the
elements is damaged, it is replaced.
At the lower part of the antenna there is a service hatch, through
which the cables and connectors are accessible. For some service
operations, such as those involving the RBD121 Antenna Amplifier
and Switch, the dome must be removed and the antenna reflector plate
tilted upwards.
In case any of the antenna elements seems to be insensitive, the most
common reason is a loose cable connector or a malfunction in the
antenna switching unit.
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Basic Troubleshooting
If the antenna operates poorly as a whole, check first that the DC
supply input is found at the end of the antenna cable. If the supply
voltage is in order the fault is possibly in the antenna amplifier.
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Chapter 6 ____________________________________________________________ Technical Data
CHAPTER 6
TECHNICAL DATA
This chapter provides the technical specifications.
Table 2 Telemetry Antenna RB31 Specifications
Feature Specification
Antenna
Frequency range 400 … 406 MHz
Horizontal directivity 8 dBi
Vertical directivity -3 dBi
Polarization near horizon Vertical
Polarization at zenith Circular
Number of corner reflectors 6
Amplifier
Gain 20 dB typical
Noise figure <2 dB
Power input +10 … 12 VDC, 130 mA through RF
cable
Output impedance 50 ohms, VSWR <1.5
Telemetry range
Telemetry range with RS92-SGP
radiosonde
350 km under normal
sounding conditions
Mechanics
Connector Coaxial 7/16
Maximum diameter 1.1 m
Height without pedestal 0.8 m
Height with pedestal 1.55 m
Weight 32 kg
Standard cable length 33 m (greater lengths possible
with low-loss cable)
Environmental Conditions
Operating temperature range -40 ... 55° C
Operating humidity range 0 … 100 % RH
Operating precipitation Unlimited
Maximum wind speed 65 m/s
Storage temperature -50 … +100 °C
Storage humidity 0 … 100 % RH
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