INTRODUCTION TO SIGNAL BOOSTERS

Based on FCC Class B (Broadband) Products

Copyright 1996 - 2005 Jack Daniel Co. 800-NON-TOLL
Removal of this notice or any references to
The Jack Daniel Company is a specific violation of this copyright.


GENERAL DESCRIPTION:
A Signal Booster is a device which can often be used to improve radio communications in an area where normally good radio signal levels are degraded due to obstacles in the radio path. The most common misconception in applying Signal Boosters lies in expecting a Signal Booster to operate in the same fashion (and signal levels) as a common repeater station. Signal Boosters are especially useful in many situations where conventional, trunking or paging radio signals are too weak to provide reliable communications. Specifically:

Signal Boosters should be considered especially when;

TX RX Systems has the broadest choice of models and the most experience in manufacturing these types of Signal Boosters and continues to improve and expand their products to meet any requirement, including channelized versions for locations with high unwanted signal levels. It is advisable to always contact TX RX Systems or their local representative for the latest models and for specific application assistance as well as system engineering support when you have a requirement.


FCC REQUIREMENTS:
Signal Boosters must be FCC type accepted and labeled as such when operating on any frequency regulated by the FCC.

The FCC has released specific rule for the use of signal boosters, effective July 19, 1996.
These rules allow the use of Signal Boosters within most FCC authorized radio systems without any additional licensing requirement.

The FCC has designated two classes of signal boosters:

For more regulation details refer to FCC RULES FOR SIGNAL BOOSTERS.

THIS DOCUMENT ONLY DEALS WITH FCC "CLASS B" (Broadband) TYPE DEVICES!


SIGNAL BOOSTERS VS RADIO REPEATERS:

Although Signal Boosters are sometimes confused with regular repeater stations, there are important differences in the application and design of these very different devices.
Signal Boosters have the following characteristics:

1. Signal Boosters are designed to provide additional signal strength in areas where the non-boosted signal would be adequate if there were no obstacles in the radio path.

2. Signal Boosters are not designed nor intended to be used to increase a radio systems outer edge range. In fact, the FCC rules for Signal Boosters are based on this condition.

3. Signal Boosters do not change the radio frequencies when the signal is boosted, therefore the users do not have to switch channels on their radios to use the boosted signals. This eliminates operational confusion, special user training, and additional channel selection capabilities in the radios.

4. Class B Signal Boosters can boost many radio channels at the same time which can be more economical than regular single channel repeater stations or Class A Channelized Signal Boosters.

5. Signal Boosters do not demodulate the radio signals and therefore do not require modulation adjustments or audio signal processing of any kind. Signal Boosters do not alter modulation characteristics.

6. Signal Boosters have lower output power levels than conventional repeaters.

7. In general, Signal Boosters are more compact, use less power and require less maintenance than a normal repeater.


SIGNAL BOOSTER CONFIGURATIONS:

Signal Boosters are available in several design types;

a. Class B: Fixed Gain (Non-OLC), non-channelized types, where the gain and power levels are set to meet very specific or unusual requirements.

b. Class B: Automatic gain adjusting, or OLC (Output Level Control), non-channelized types, where the Signal Booster automatically sets the gain over a wide range of input signal levels.

c. Class A: Channelized versions that only pass specific radio channels on a channel by channel basis. These are more expensive than non-channelized types and used primarily at the over- the-air (OTA) interface in areas where many high level unwanted channels exist. In complex system, these may also be required to meet FCC out-of-band emission limit requirements.

Again, this document only deals with Class B, Non- channelized, OLC type Signal Booster designs as this type is more commonly used to date. Non-OLC versions, Channelized types and customized Signal Boosters are also available from TX RX Systems.


THE COMPONENTS OF A CLASS B SIGNAL BOOSTER

The specific organization of a Signal Booster can vary greatly according to the specific application and installation requirements. In general, a Signal Booster with OLC contains;

- A gain block (a wide band, linear amplitude amplifier).

- Frequency selective filters/cavities placed at the amplifiers input and output ports.

- A special output level control (OLC) circuit.

- A power supply/regulator.

Signal Boosters may be constructed for either;

A. One-way (such as paging coverage improvement or portable talk-back only), or

B. Bi-directional Amplification (two way) duplex signal amplification, the most popular of all designs at this time.

Signal Boosters may be applied in a manner similar to a coaxial cable RF signal distribution system. Non-radiating (common) coaxial cables and/or radiating coaxial cables (sometimes called "leaky coax") can be used to route the RF signal between Signal Boosters and radio coverage areas. Multiple Signal Boosters may be connected in series to provide radio coverage for multi-story buildings, long tunnels or separated areas of communications.

TX RX Systems has power splitters, antenna decouplers and antennas which permit complex RF communications signal distribution and signal branching applications.

AC and/or DC power operation is possible, as well as battery back-up operation. In some cases, power for the Signal Booster may also be applied at the Signal Booster from a distant location using the coaxial cable as a DC power cable.

TX RX Signal Boosters are available in weatherproof stainless steel NEMA cabinets suitable for outdoor or unprotected locations, lower cost painted steel cabinets or rack mounted systems.


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