MAT Jaybeam 7501 450 User manual

- 7501450 -
7501 450
Plan Vertical
DIPÔLES VHF & UHF ALIMENTÉS À LA BASE
Toutes les bandes de fréquences PMR se retrouvent ici, ainsi que les bandes
aviation VHF et UHF (types 7500 et 7502).
Type 7501 450
Fréquences disponibles (MHz) 420 - 470
ROS <1.5 : 1 Typique
<1.8 : 1 Max.
Gain (dBd) 0
Impédance (Ohms) 50
Polarisation Verticale
Rayonnement plan vertical
(-3 dB) 80°
Puissance Maximum (Watts) 100
Sortie N femelle
Fixation Brides de fixation
intégrée
Longueur (cm) 58
Poids (kg) 0.95
Charge au vent @ 45 m/s (N) 16
reserve the right to modify or amend any antenna or specification without prior notice
Jaybeam Limited
Rutherford Drive, Park Farm South Wellingborough,
Northamptonshire, NN8 6AX, England
Tel: [phone] Fax: [phone]
WWW.jaybeam.co.uk
MAT Equipement
ZI La Boitardière, Chemin du Roy
37400 Amboise
Tel: [phone], Fax: [phone]
WWW.matequipement.com

- MA462DS13 -
MA462DS13
Plan Vertical
ANTENNE GROUND PLANE 26,745 MHz
Type MA462DS13
Description Fouet 2 éléments
Fréquence (MHz) 26,745
Bande passante (% Fréquence centrale) ± 2
ROS < 1,5
Gain (dBd) 0
Impédance (Ohms) 50
Polarisation Verticale
Puissance Maxi. (Watts) 250
Sortie UHF (S0239)
Fixation 2 vis de blocage
sur tube ø 40 mm
Matériaux Aluminium traité
et fibre de verre
Longueur (cm) 260
Poids (kg) 2
Surface au vent (m2) 0.05
reserve the right to modify or amend any antenna or specification without prior notice
Jaybeam Limited
Rutherford Drive, Park Farm South Wellingborough,
Northamptonshire, NN8 6AX, England
Tel: [phone] Fax: [phone]
WWW.jaybeam.co.uk
MAT Equipement
ZI La Boitardière, Chemin du Roy
37400 Amboise
Tel: [phone], Fax: [phone]
WWW.matequipement.com

VHF AND UHF ANTENNA INSTALLATION INSTRUCTION
1. PREFACE
1.1 Introduction
1.2 Scope of the installation instruction
2. GENERAL ASPECTS OF PAGING COVERAGE
2.1 General
2.2 Receiver types, sensitivity
2.3 Data to be considered
2.4 Field coverage test
2.5 Coverage of areas with poor reception
2.6 Mufti- transmitter system
2.7 Theoretical approach
3. ANTENNA TYPES AND THEIR CHARACTERISTICS
3.1 Groundplane antenna
3.2 Dipole antenna
3.3 Collinear antenna
3.4 Whip or helicoil antenna
4. ANTENNA SITING
4.1 General
4.2 Groundplane antenna
4.3 Screening
4.4 Reflection
4.5 General guidelines
5. RADIATING CABLES SPECIAL SOLUTIONS
5.1 General
5.2 Radiating coaxial cable
5.3 Long wire antennas
6. COAXIAL CABLE
6.1 General
6.2 Standing wave ratio. SWR
7. MOUNTING INSTRUCTION FOR GROUND PLANE ANTENNA

1. PREFACE
1.1 Introduction
The VHF and UHF paging systems require an antenna to transmit the paging signals from the central equipment to the signal
receivers or transceivers. The paging system can use 5 Watt transmitters or low power (2 Watt VHF or 1 Watt UHF) transmetters
mounted on or near a master operator console. The low power transmitters may be equipped with a built-on helicoil antenna or an
outdoor antenna. The 5 Watt transmitters usually use an outdoor antenna.
The antenna (or antennas) should be installed in such a way that adequate reception of the signais is obtained wherever required.
This should, as a matter of fact, be obtained with a minimum of costs, i.e. on the most convenient place ensuring sufficient field
strength for the receivers
Always make sure the installation of antennas, their location and height, as well as transmitters, their location and output power,
comply with local regulations. Always check the local telecommunications authority requirements.
It is very useful to try various antenna locations to establish the most effective one.
1.2 Scope of the Installation Instruction
The scope of this instruction is to give a guideline for antenna installation. Because there are so many differences between one site
and the other, in number of buildings, construction of buildings etc., it is not possible to give exact data for each possible case. The
information in this manual, together with some practical experience, will enable you to select the most suitable position for the
antennas for the different applications. Also some special applications are indicated for instance in high rise buildings and tunnels.
On-site tests, using a demonstration set for instance, give the best aerial location, avoiding areas of poor or no reception of the signal,
and inform you if more transmitters will be necessary to cover the site.
2. GENERAL ASPECTS OF PAGING COVERAGE
2.1 General
An essential condition for good reception is that the antenna is optimally sited. The capacity to transmit over the greatest possible
distance is usually of secondary importance. What is important, is that the transmitted signals reach, or penetrate into places like
basements, lift shafts, stair wells etc. Places in which reception is desired can generally be served if the site of the antenna is chosen
with care.
The coverage range and penetration depend on field strength and receiver sensitivity. The field strength in turn depends on output
power and antenna location with respect to obstructions like walls, buildings, hills etc.
2.2 Recelver types, sensitivity
Basically, there are two types of transmission in the present paging system:
1. Digital code transmission for bleep and display receivers.
2. Analogue speech transmission for receivers with additional speech facility.
Generally, a receiver requires a stronger field strength to give good speech performance than for bleep and display only.
2.3 Data to be considered
The following data of a certain site have to be taken into consideration to determine in advance the location(s) of the antennas
and transmitters:
1. Size of the site to be covered.
2. Details of the building: a. position; b. height; c. construction: - presence of basements; -
amount of reinforcement; - type of windows.
3. Topography of the site, whether flat or hilly.

2.4 Field coverage tests
The first step is to identify the special problems of the site by carrying out a field intensity test there. This will locate
any "weak" or "dead" areas and by trying different antenna locations the most suitable position will be found.
If a single transmitter will not give sufficient coverage of the whole site, there are several methods of improving
the situation. The following methods are possible:
1. Increase the power of the transmitter (using a linear amplifier). However, there are a number of objections
to this method: a. local restrictions on antenna power;
b. doubling the transmitter power to the antenna only gives an increase in range
of a factor of 1,19 (fourth root).
2. Increase the antenna height. This is also probably limited by local regulations.
3. Use an antenna with gain in certain directions. Once again this solution can possibly be ruled out by local
regulations.
4. Use radiating or leaky coax cable, or long wire antenna.
5. Use splitters and extra antennas.
6. Use one, or more, transmitters and antennas.
The solution chosen will depend on a large number of factors.
2.5 Coverage of areas with poor reception
Dependent on the size and situation of problem areas there are a number of practical solutions for areas with poor
reception.
The coaxial supply lead of the antenna can serve as a radiator in elevator shaft corridors etc.; this has a range of up
to 5 metres from the cable. Distances of up to 30 metres will be served if radiating coaxial cable is used (see chapter
5).
Power splitters and extra antennas can be used. The power loss caused by the cable, or the splitter, are usually of
minor importance to the range of the main antenna.
For buildings in an area with good field strength outside but weak reception within (shielding caused by reinforced
concrete, metal plating etc.), improvements can be made by using two antennas - one outside and one inside
-connected by a short cable.
2.6 Multi-transmitter system
If none of the foregoing methods can improve reception in problem areas a multi-transmitter system using one or more
slave transmitters will be necessary.
The aim of the slave units is to improve penetration into a "dead" area, such as a basement or heavily reinforced
structure and/or to increase range.

3. ANTENNA TYPES AND THEIR CHARACTERISTICS
3.1 Ground plane antenna
The most commonly used antenna for VHF systems is the ground plane antenna.
Characteristics:
- Can easily be installed on a metal mast. -Gain is 0 dB, omnidirectionnal. - Its beam
has a slight elevation of 10°. - Impedance 50 Ohm.
Straight below and above there are relatively weak zones.
3.2 Dipole antenna
The radiation characteristics depend on the mast or other construction on which it is
mounted.
a. Non conductive mast. This is not a commonly used method because masts or
fixtures are usually made of metal or steel, but if non conductive, then its
characteristics are the saine as for the ground plane, however, without elevation. To
be used as inside antenna, if needed, where penetration is difficult, for instance
inside rooms of nuclear power stations etc. The dipole can be used on places where
groundplane is not desired for aesthetic reasons.
b. Conductive mast.
The mast or steel fixture reacts as a reflector. Characteristics: - Can easily be
installed on a mast. - Gain is 2 dB in "front direction". - Front to back ratio + 6 dB. -
Impedance 50 Ohm. - To be used on relatively long and narrow sites.
A gain of 2 dB is a coverage range gain of 1.41 (root 2).
3.3 Collinear antenna
This is usually a wide band antenna with the saine characteristics as the normal dipole.
The collinear antenna is the antenna normally used for the UHF system.
3.4 Whip or helicoil antenna
The whip or helicoil antenna is an electrically shortened antenna, suitable to be mounted directly on a low power transmitter (2
Watt VHF, 1 Watt UHF), which can in turn be mounted on a master operator console or on the wall. The combination forms a
complete system: combined operator console, code generator and transmitter. This combination is to be used for the smaller
buildings or sites where small areas are to be served.
The performance is relatively poor with respect to a ground plane
antenna. The resufts are slightly better for the UHF system because the aerial length approaches
the 1/4 wave length.
Characteristics:
a. VHF
- length << 1 /4 λ, ;
- gain - 3 dB with grounds
- gain -12 (to - 12 dB) with poor or without ground.
b. UHF
- length ≈1/4 λ, ;
- gain 0 dB with ground i.e. set stands on grounded metal surface, e.g. a filing cabinet or metal
deck.;
-
g
ain - 12 dB without or
p
oor
g
round.

4. ANTENNA SITING
4.1 General
This chapter describes antenna siting for a ground plane antenna but applies also for other antenna types, of course.
4.2 Ground plane antenna
The externat antenna usually applied in the paging system is a vertical dipole with ground plane rods.
The most effective radiation direction for this type of antenna is in the horizontal plane, whilst the signal
strength vertically above and below the antenna is comparatively weak, especially in the area below
the ground plane rods.
In ideal conditions, the field strength at a given transmitted power depends solely on the distance from
the antenna. The field strength then decreases linearly with the distance. If, however, there are
obstacles in the path of the signal, two effects occur which can materially affect the propagation of the
electromagnetic radiation, these being:
- attenuation due to screening;
- reflection.
4.3 Screenlng
Although all materials resist the passage of electromagnetic radiation to a greater or lesser degree, the resistance to
passage of the signal is greatest when a metal obstacle, screening the radiation, is situated between the transmitter and
the receiver. This can be the situation when steel structures are located in the area to be served or when the receiver is
in use inside buildings whose structure is of reinforced concrete.
How strong the screening effect is, depends on the nature of the obstacle and the number of screening layers. The distance
between. the receiver and the transmitter is of much less importance. It will therefore be obvions that good reception in the
basement of a high building is more unlikely if the antenna is mounted on the saure building, for the signal must then pass
through a succession of reinforced concrete floors before reaching the receiver. It will be equally obvions, on the other hand,
that good reception is assured if the antenna is at the side of the building allowing the radiation to pass through relatively thin
watts and windows, the more so because the signal strength below the antenna is, in any case, weaker than that at the side.

4.4 Reflection
When electromagnetic radiation strikes a surface, part of the radiation is allowed to pass or is absorbed, and part is reflected. The
pattern and degree of reflection depends on the nature and size of the reflecting surface and the angle at which the radiation
The reflected radiation can interfere with the direct radiation. Buildings contain a large number of reflecting surfaces, in the form of
floors, walls and ceilings, which give rise to complex interference patterns, the effect of which is to amplify the signal at certain
points and weaken it at others. In unfavourable conditions, reception in certain places may be quite impossible. This is especially
true of places situated near the structure supporting the building -between thick pillars, in stair wells, beside lift shatts etc. Unlike
those places at which, owing to absorption or screening of the radiation, no reception is obtainable, "dead spots" resulting from
interference engendered by reflection are usually sharply defined and limited in extent. Dead spots are not predictable. Shifting the
antenna can usually remedy matters at dead spots, but the risk is that it will give riss to new dead spots elsewhere.
4.5 General guidelines The following lines of guidance on situating the antenna should be noted. If a building or group of buildings
is to be served, situating the antenna on the highest point of the structure is the worst possible thing to do, for, in such
circumstances, reception is better at all surrounding points than it is in the building itself.

Should the building comprise a high and low section, very good resuits can be obtained by situating the antenna on the low
section. The antenna then beams the signal horizontally - the most effective way through the high section, the radiation
requiring to pass through only a limited number of thin walls instead of a large number of fixed concrete floors. What is more,
the pattern of reflection occurring between floor and ceiling at every level facilitates uniform distribution of the field. Should
there be cellars below the low section to be covered, however, it is best not to situate the antenna directly above these since,
otherwise, reception in the cellars might be bad.
Where only one building must be served, the antenna may be situated some tens of metres distance from the building,
on a porter's lodge, perhaps, or on a ground mast 10 -15 metres (30 - 50 ft ) in height.
Where this is impossible, and if the building is of uniform height, it is generally best to mount the antenna on a comer of
the building, as far as possible from the elevator shafts.

Where an outdoor area must be served, the antenna is best mounted at a height of 10 - 20 metres (30 - 60 ft) in the
centre of the area.
If high buildings or steel structures are found in the area, however, reception in buildings in the "shadow" of these obstacles
may be inferior. Such an effect can nevertheless generally be avoided if care is exercised in choosing the site for the
antenna. Moreover, the signal will be able in many cases to reach these
Il shadow areas" via reflection against other
buildings.
The antenna must always be mounted a minimum of 4 metres (15 ft) above the ground or roof, and the horizontal distance
between the antenna and the walls and such like must at least be 15 metres (50 ft) this with a view to prevent both reflection
and standing wave patterns.
5. RADIATING CABLES, SPECIAL SOLUTIONS
5.1 General
Special attention becomes necessary when paging signais are required to cover areas where RF propagation with
conventional antennas is difficult. For instance in mines, tunnels or high rise buildings. The electromagnetic fields, radiated
by an antenna in a tunnel, decreases exponentially due to multiple reflections and vehicle traffic Metal construction can
invoke the Faraday effect in high rise buildings. Radiating coaxial cables or long wire antennas can overcome these
problems.
5.2 Radiating coaxial cables
A radiating coaxial cable is a cable of which the outer conductor (the screening) has slots along its length. It thus leaks
(radiates) energy which is uniformly distributed over the whole length of the cable. The cable has a characteristic
impedance of 50 Ohm and, of course, must be terminated with a 50 Ohm RF load, which can be an antenna to cover a
surrounding area. The cable must be separated from the supporting walls by some 10 cm or more, especially if the wall is
a steel construction. Although relatively expensive, it can be the deciding factor in making a system acceptable on
performance.