Zartek ZA-711 User Manual - page 10
Communication Range
Range will depend on the type of terrain that you are communicating
across.
The ZA-711 uses the VHF (Very High Frequency) band and will be
subject to similar obstacle interference as cellular phones. The radio
works indoors as well as outdoors. Typical rough estimate ranges for
different terrains are:
Indoors or Shopping centre 600m-1500m
Building 5-30 stories,
City centre & dense bush 500m-3km,
Residential & over water 2-6km,
Farmland 3-8km,
Top of mountain or building (line-of-sight) 15-50km.
When you press the PTT talk button a signal is transmitted and the signal
floods the area in all sideway directions. The signal travels in 3 different
ways:
1) Penetration: The signal can go through materials such as wood,
plastic, cement and fabric. The denser the material or more built up the
environment the weaker the signal will become. The signal cannot go
through solid metal or very large solid land structures such as a hill or
mountain. Metal acts like a shield and that is why the performance from
the inside of a vehicle (car or 4x4) will be less than outside and an
external car antenna kit is recommended to improve communication.
2) Reflection: The signal cannot go through metal or very large structures
such as a hill or mountain, but it can bounce off (like a mirror), go around
and reflect in other directions as well. This happens at the speed of light.
3)Line-of-sight: Line-of-sight is when there are no obstructions in the path
between the communicating parties. The higher up you go the further you
can see, so the larger the line-of-sight distances will be. Generally you
can talk to wherever you can see, which is why the coverage in a valley is
much less than the coverage from on top of a hill.
Ensure that there is nothing blocking the antenna. The less metal in close
proximity (0-2m) the better the range. There may be external interference
from electrical equipment (power lines or factories) or natural causes
(moisture in the air or storms) that may vary depending on the location
and the weather.