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may suffer noticeably less transmitter range. In the severest of circumstances, this interference may cause the system to operate erratically, which may include
arming and disarming or going into the panic mode due to the interference. This extreme form of interference, fortunately, is quite rare, as the FCC carefully
regulates the radio frequencies that are assigned to, and transmitting output power of RF devices.
Interference comes from many sources, including some which occur naturally. Any device which is powered by electricity or which has electronic circuitry
can produce electromagnetic or RF interference. Sometimes difficulty is encountered from electrical components and circuits within a vehicle, or by mounting
two receivers too close together. In these instances, shielding the system's CPU to block the interference may
solve the problem. This is easily accomplished by wrapping the CPU in either the flexible metal shielding
designed for automotive audio noise problems or aluminum foil tape and grounding the shield. Care
should be taken to avoid shorting any of the CPU's connectors or terminals and to ensure that as
little of the antenna wire is blocked by the shielding as possible. Grounding the shield is
accomplished by molding the material around one of the mounting "ears" and using a
small bolt and nut to secure a ground wire with two
ring terminals between the CPU and chassis ground.
There are several ways to increase the effective
range of the security system's transmitter. The most
basic approach is to remember to route the Black
antenna wire as high in the vehicle as possible,
avoiding metal as much as possible. The metal struc-
ture of the vehicle blocks the transmitter's RF signal,
so if the CPU is mounted deep into the vehicle, such
as in a kick panel, for instance, the transmitter's
operating range will be limited unless the antenna
wire is routed high and away from metal. On many
cars, the "A" pillar interior trim panel overlaps the
windshield. Tucking the antenna wire behind this
trim is an excellent method of obtaining maximum
range. Other options include taping the wire to the
bottom of the dash pad or routing it below the rear
package shelf panel. The antenna wire may also be extended, with the maximum recommended length added to the existing antenna wire being 26 inches (which
may be doubled) of 22 gauge wire. It should be remembered, however, that too much transmitter range can also produce some undesirable operations. Such
a security system is more likely to be accidentally disarmed, especially when the operator is too far away to hear the siren's confirmation chirps. Extreme
operating range will also make the system's receiver more susceptible to extraneous interference. Adequate operating range of 50-100 is acceptable, and it is
normal for the range to be greater in rural areas as compared to urban areas. The fact that range is often very poor in downtown areas, is the result of greater
amounts of RF interference, compounded by the tendency of such signals to be reflected off the tall buildings.
Antenna Options For Better Range.
Page 8
The optional AU-ANT ex-
tended range antenna is
shown mounted in two good
locations: blocked from the
driver's view by the rearview
mirror (avoid sunshading)
and beside the "A" pillar trim.
The AU-ANT should be
mounted as high as possible.
An extended antenna
wire can be routed
around or behind the
dash pad and concealed
behind the "A" pillar
interior trim panel.
Black Antenna Wire
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