emergency relief items compendium of generic specifications

1. TELECOMMUNICATIONS & POWER SUPPLY
General
The success of an emergency relief operation is highly dependent on an efficient communications network. Since the public
telecommunications network will, during an emergency situation often be saturated or out of order, the communications
network for a relief operation should be based on equipment which is brought into the disaster area and which can work
independently of local support. It is therefore extremely important that all the communications equipment to be used in
the field is able to operate from a 12 VDC power supply, possibly supported by a solar power system or small portable
generating sets ( with output 12 VDC ) as backup. The different communications systems needed in a disaster relief
operation can normally be divided into three categories, each of which requires different kinds of equipment:
Short-Range Communications
Hand-held VHF radio systems are to be used locally within a very limited distance from the base (2-10 KM depending on the
terrain).
a) Public Addressing (PA) Equipment
As one-way communications equipment, the hand-held power megaphone can be very useful when a large number of
people assembled in a small area need to be informed simultaneously.
b) Hand-held & Base Station VHF Equipment
For short-range communications between individuals in a local area (normally within "line of sight"), and between these
individuals and a base, it is essential to have a reliable, foolproof and professional radio-telephone system installed
(often called a "walkie-talkie" system). Attention should be paid to the confidentiality/privacy of all communications
which are not encrypted.
Medium-Range Communications
Portable and mobile HF radio equipment. VHF equipment with possible use of a repeater station can be used in a regional
area. When communications beyond the immediate area around the base is needed, the equipment described above needs
to be supplemented with additional equipment. In order to cover a larger region around the base and overcome the "line
of sight" limitations for the VHF equipment, it will often be necessary to use VHF repeater station equipment and make use
of mobile VHF and HF equipment.
The mobile equipment is often the same as that used at the base station, but with the hardware modified for vehicle
installation.
Long-Range Communications
HF radio and satellite equipment for communications with the outside world, HQ etc.
For long-range communications there are basically two different methods to choose from: HF-radio systems or satellite
systems. Each method requires completely different types of equipment with advantages and disadvantages as explained
below.
a) HF-Radio Systems
HF-radio (shortwave radio) is the traditional method for medium and long-range voice and telegraphic communications. HF
SSB communications is more reliable than VHF or UHF communications, especially where mountainous terrain or distances
over 14 miles are encountered. HF radio signals (2 - 30 MHz) may be received at distant locations using either ground wave
or sky wave signals. Ground wave signals follow the contour of the ground in hilly regions for 1 to 90 miles, depending on
frequency. At distances greater than 50 miles to several thousand miles, sky signals which bounce off the F2 layer of the
ionosphere are involved.
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