4. MICROWAVE LINK DESIGN
CONSIDERATIONS
In putting up microwave links, the different
considerations are made:
Site Selection
Equipment selection
Tower Selection
Power Equipment
Lightning Protection
5. SITE SELECTION
In locating the sites, the following factors should be
considered:
Terrain mapping for possible obstructions;
Geographical location, for possible line-of-sight path
obstruction;
Adequate source of power and water;
Population on each site and;
Be in the vicinity of any popular landmark or a City in
the region.
The proponents also considered the topographic map
of every province covered by Region 3 for
establishment of each site.
6. EQUIPMENT SELECTION
Microwave Antenna
The microwave antenna that is to be chosen:
Must have high antenna gain;
And must not be too heavy and large for easy mounting
in the tower.
7. EQUIPMENT SELECTION
microwave radio that is to be chosen must have:
A frequency at which the links is to be operated;
low receiver sensitivity value;
High transmitted output power;
An indoor and outdoor unit installation for eliminating the
use of waveguides for transmission;
And must be a user-friendly interface for simple
maintenance management.
8. EQUIPMENT SELECTION
Automatic Transfer Switch
The ATS must have the ability to be switched on and off
to different sources that is the main power source and
the backup source.
Air Conditioning Unit
The site must contain an air conditioning unit for proper
cooling and must accommodate the whole room to
maintain the proper temperature in which all the
equipments are stored so that overheating and
malfunctioning of the equipments is prevented.
9. TOWER SELECTION
The tower used must possess the following:
The capability of the tower to hold loads such as
antennas and cables prior to construction;
The type of soil wherein the tower is raised must also be
considered for any ground movement to prevent the
tower from swaying;
The height of the tower must be enough in order to
avoid obstructions;
The anticipated wind loading was identified under harsh
condition and additional loading.
10. A stand – by power equipment should be provided
for possible power interruptions at the microwave
site to maintain operation.
Generator
Uninterruptible Power Supply
POWER EQUIPMENT
11. LIGHTNING PROTECTION
The lightning protection that will be used must
contain the appropriate conductive paths for
lightning currents and be able to disperse
atmospheric discharge in order to prevent surge
current to enter the equipments and sustain safety
in the facility.
12. GROUNDING PROTECTION
The grounding equipment must be installed at
every equipment inside the facility and must be
coordinated with the lightning protection in order to
prevent abrupt surge entering to the equipments
thus making the equipments safe.
13. OBSTRUCTION LIGHTING
21 feet – 120 feet:
Use 2 obstruction lights;
151feet – 300 feet:
Use 2 obstruction lights at one-half way level of the
tower & a beacon light at the top of the tower;
301 feet – 405 feet
Use 2 obstruction lights at 2/3 way level and a beacon
at the top;
405 feet and above
Use various light combinations stated.
14. SAMPLE DESIGN
The following are the objectives of the design:
To construct a feasible microwave link between:
Bamban, Hermosa, Bataan (Site 1) and Pulung Bulu,
Angeles City, Pampanga(Site 2) with the frequency of
5Ghz;
To achieve an overall system reliability of 99.999999%;
17. GREAT CIRCLE DISTANCE CALCULATION
The formula in getting the Great Circle Distance is as follows:
A = |LONGITUDE 2 - LONGITUDE 1|
b = 90° - LATITUDE 1
c = 90° - LATITUDE 2
cos a = (cos b) (cos c) + (sin b) (sin c) (cos A)
Conversion factor: 1° = 60 nautical mile
1 nautical mile = 1.151 statute mile
1 statute mile = 1.609 kilometre
18. COMPUTATIONS:
Known Data
Site Longitude Latitude
A.
Bamban, Hermosa, Bat
aan
120°25’28.33” 14°48’31.96”
B. Pulung Bulu, Angeles
City, Pampanga 120°36’12.07” 15°8’1.95”
20. ANTENNA ORIENTATION CALCULATION
Where:
C = difference of the longitudinal coordinates of the sites in a hop
X = the computed coordinate of the first site
Y = the computed coordinate of the second site
26. TRANSMISSION CALCULATION
The calculation of the power dissipation at certain
points in the system wherein we can determine at
what level of the signal will be received by the
receiver part of the microwave link. The points are
as follows:
PT = P1
P2 = PT – TLLTX
P3 = P2 + AGTX
P4 = P3 – FSL
P5 = P4 + AGRX
P6 = P5 – TLLRX = RSL
