RF Technologies ART400, Инструкция по установке, эксплуатации и программированию

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Commercial In Confidence
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important but for distant stations the loss is very important. As a rule of thumb, never
operate a system with a loss of more than 3dB.
To illustrate the point, a 3dB loss in the feeder will result in a 50% loss in transmitted RF
power and a 50% reduction in the received signal strength. Therefore, double the received
signal strength will be required for the same bit error rate.
Although increasing the RF power will compensate for the loss in transmitted power,
there is no effective way to improve the received signal strength.
Coax cable should be installed in accordance with the manufacturers’ instructions, with
cable runs kept as short as possible. Sharp bends, kinks and cable strain must be avoided
at all costs. If long term reliability is required, the cable must be securely mounted to avoid
excessive movement and longitudinal strain, due to high winds, rain and snow.
4.5.10 SIGNAL LOSS VERSES CABLE LENGTH AT 500MHZ
Cable Type Attenuation Attenuation
per 100ft per 100M
RG58 13.0dB 37.0dB
RG213 6.0dB 17.5dB
LDF2-50 3/8inch Foam Heliax 2.44dB 8.0dB
LDF4-50 1/2inch Foam Heliax 1.60dB 5.26dB
LDF5-50 7/8inch Foam Heliax 0.883dB 2.9dB
LDF6-50 1-1/4inch Foam Heliax 0.654dB 2.15dB
LDF7-50 1-5/8inch Foam Heliax 0.547dB 1.79dB
4.5.11 COAX, CONNECTORS:
50 Ohm coax connectors of a good quality should be used, termination must be in accordance
with the manufacturer's specification, any special tools required to terminate the connectors
must be used. Connectors exposed to the environment should be sealed to prevent the
ingress of moisture. If the cable is penetrated by water a high loss will occur and the cable
will need to be replaced. Once assembled it is advisable to test the cable and connectors for
open and short circuits.
4.5.12 VSWR MEASUREMENT:
Voltage standing wave ratio (VSWR) is the ratio of detected volts from the forward RF
power, to the detected volts from the reflected (returned) RF power. This ratio is used to
measure the combined coax cable and antenna match. A good match will ensure that most of
the RF Power is radiated, whereas a bad match will result in the reflection of a large amount
of the power, thereby reducing the transmitter's range. A perfect match will give a 1:1 ratio
and bad match will give 2:1 or higher. For guidance, a good system will measure between
1.2:1 and 1.5:1.
4.5.13 Lightning Arresters
At high or exposed sites, the use of a lightning arrester is recommended.
This in-line device fits between the antenna and the product with an earth strap connected to
ground. Should a lightning strike occur, the most of the energy should be diverted to ground
leaving the equipment with little or no damage.
4.6 MOUNTING & INSTALLATION