5.8GHz Day-Night Camera Series Manual Rev. A
6
Ground Plane
If the radio devices are not mounted high enough above obstructions, the signal strength will be
seriously reduced; therefore your distance will be reduced. The signal will literately bounce up and
away from your intended target. This is known as a negative ground plane effect. The ground plane
could not only be the ground you stand on, but could also be the rooftops of cars or distant buildings.
See Figure 3
.
If we have a choice, place the transmitter/receiver enclosures, or if external antenna, on
the edge of the roof looking AWAY from the building, rather than installing them in the middle of the
roof , shooting across the top of the roof.
See Figure 4
.
This is particularly important if we have a
metal roof that tends to deflect signals away from the target.
Also consider any obstruction that may
get in the way, like another roof or a tractor-trailer that may pass through your “line of sight”.
.
Trees Grow!
If we install the video link in the winter, the leaves that come out in spring may eliminate your wireless
link. Are you trying to transmit through trees? Then you will need to seriously consider how much
range will be lost. A field test is always the best way to find out. Speak to a VideoComm Technologies
Tech for a possible solution.
Unusual Traffic
Watch out for unusual traffic in your transmission path. For example, a dump truck with the back
elevated while dumping a load can be much taller than expected. Tractor-trailers or other large vehicles
may be a factor if trying to transmit over a highway. Metal obstructions between the antennas cannot
be ignored including electrical transmission lines that may not be obvious in the distance. Each high
voltage wire crossing your path can be the equivalent of transmitting past an eight-foot thick steel pipe.
Microwave towers may look fragile, but they can be as good as or equal to a solid steel door for
blocking transmission.. The higher the transmitter and receiver are in the air, the higher the success
rate.
Things that block transmission
Things that block transmission
are not always obvious. Here are some of the most common pitfalls:
•
Water, or anything with water in it (people are 98% water). Snow & rain can reduce your
distance.
•
Steel, or anything with steel in it---steel-reinforced concrete (rebar) or metal window
screens, or a tool-room cage. Aluminum siding, and energy-saving foil on the insulation in
the walls are sneaky killers for radio waves. Some metallic paints or metallic wallpapers
also block signals.
•
Mirrors block transmission, because the “mirror” consists of a metallic backing on the glass.
•
Lead windows will kill radio transmission; also windows that are UV coated may have thin
metal energy-saving film.
•
High Voltage transmission lines (physically they look small, but for video transmission
purposes, they might as well be 8-foot diameter metal sewer pipes.
•
Other materials like brick, drywall or wood, will also cut down on the signal, depending on
water content.
