RF attenuators reduce the strength of an RF signal. Typically the RF signal is carried on a coaxial cable and an RF attenuator is used in line with that cable. They are also in circuit designs and microwave applications. The need to reduce an RF signal may not immediately be obvious to the casual user who may have needed a signal amplifier for TV reception after struggling with low signal.

RF attenuators are necessary devices that can make a transmitter or signal distribution system suchSource: CC BY-SA 3.0 / Joe Ravi as cable TV more reliable by allowing levels to be balanced. The more common use of an RF attenuator is for test and measurement where often the signal level is too strong for the test equipment.

RF attenuators are essentially electrical resistors that are put in line with an RF signal and reduce the signal strength by converting some amount of RF energy into heat. The amount of resistance used is what determines the amount of attenuation. RF energy is not as simple as DC so the type of resistors chosen and how they are used is important. RF likes to radiate, so two closely spaced connections may act like a short depending on the frequency of the RF signal. Wirewound resistors won’t work for attenuation because they act like inductors instead.
Read more...

Source: Electronics 360
              Daniel Franklin