Amplifiers and attenuators
. . . .

---

Amplifiers

• An RF amplifier takes the signal that is generated by the transceiver, increases it, and sends it to the antenna.
• Unlike the antenna providing an increase in gain by focusing the signal, an amplifier provides an overall increase in power by adding electrical energy to the signal, which is referred to as active gain.
• Amplifiers can be purchased as either:
  • Unidirectional: Unidirectional amplifiers perform the amplification in only one direction, either when transmitting or when receiving.
  • Bidirectional:  Bidirectional amplifiers perform the amplification in both directions.
• The amplifier’s increase in power is created using one of two methods:
  • Fixed-Gain: With the fixed-gain method, the output of the transceiver is increased by the amount of the amplifier.
  • Fixed-Output: A fixed-output amplifier does not add to the output of the transceiver.
• It simply generates a signal equal to the output of the amplifier regardless of the power generated by the transceiver.
• Since most regulatory bodies have a maximum power regulation of 1 watt or less at the intentional radiator (IR), the main purpose of using amplifiers is to compensate for cable loss as opposed to boosting the signal for range.
• When installing an amplifier, install it as close to the antenna as possible. Because the antenna cable adds loss to the signal, the shorter antenna cable will produce less loss and allow more signal to the antenna.
• Additionally, it is important to note that an amplifier increases noise as well as signal strength.
• It is not uncommon for an amplifier to raise the noise floor by 10 dB or more.
  

Attenuators

• In some situations, it may be necessary to decrease the amount of signal that is radiating from the antenna, even the lowest power setting of the transceiver may generate more signal than you want.
  
• Attenuators are typically small devices about the size of a C-cell battery, with cable connectors on both sides.
• Attenuators absorb energy, decreasing the signal as it travels through.
• You can add a fixed-loss or a variable-loss attenuator.
  • Fixed-loss attenuators
    • provide a set amount of dB loss
  • Variable-loss attenuator
    • has a dial or switch configuration on it that enables you to adjust the amount of energy that is absorbed.
    • Variable-loss attenuators are often used during outdoor site surveys to simulate loss caused by various grades of cabling and different cable lengths.
    • variable attenuator is to test the actual fade margin on a point-to-point link. By gradually increasing the attenuation until there is no more link, you can use that number to determine the actual fade margin of the link.
      

---

Reference:
Coleman, David D.,Westcott, David A. CWNA: Certified Wireless Network Administrator Official Study Guide: Exam CWNA-106 Wiley.