Wireless CCTV - To Be or Not to Be

CCTV Camera Europe are often asked about wireless CCTV transmission
- it would be so convenient to place cameras at the required
locations, locate the digital video recorder at a suitable location
and let the images drift over the airwaves without the burden of
having to run any cables. This ideal is possible, sort of. The snags
are cost and quality.The starting point is that cable connections are
cost effective, without quality issues, and power cables have to be
attached to the cameras anyway, so that the wireless option only makes
sense when a road, or someone else's property, needs to be crossed.
The extra cost of between �8.00 and �15.00 per camera can then be
justified. The issues are power source, and distance. Distance
determines whether an analogue or digital signal is required.
Power:
All cameras require power to operate. Even the best battery will only
keep a camera powered for days rather than weeks, creating a high
level of maintenance. While solar power can be theoretically be used,
existing technology for 24/7 operation, in all circumstances, is too
complicated and expensive. A wireless camera really must be placed
where there is mains power.
Analogue systems are the most cost effective, but they have distance
limitations. Analogue systems are free to air and will allow you to
cross a road etc., but their useful range is realistically capped at
80 meters. This can be expanded to 250 meters with specialised beam
antennas. There will, however, be a marked reduction in picture
resolution as the signal band-with needs to be reduced to transmit. As
a rule of thumb the picture degradation would be comparable to the
difference of a DVD picture over VHS. Where pictures might be used
for evidence in a court this degradation in quality should be avoided.
Digital transmission systems must be deployed to achieve ranges of up
to 800 meters at full image quality. Digital systems have a cost of
�2k to air. A license from XXXXXX is required. The determining factor
is the picture quality relative to the potential uses of the recorded
pictures. Thus digital cameras are required over distances greater
than 80 meters if the identification of people is required, while if
the camera is required to merely monitor an area, a poorer analogue
signal might be sufficient.
Line of sight: Both analogue and digital systems rely on line of sight
- that is both transmit and receive antennas need to be able to "see"
each other clearly. Low density vegetation like leaves can play havoc
on a transmission path - it is not unusual for a wireless system to
function perfectly in winter only to stop working in the spring when
foliage gets in the way. One quirk of the high frequency waves is that
they can often be reflected by flat dense surfaces like walls etc.
This can lead to a non line of sight, or rather a reflected path
transmission, in special circumstances.