one step if the attenuator 211 lowers the attenuation degree by the unit of one step the solver 239 controls the attenuator 211 to increase the attenuation degree by the unit of one step fig4 is a block diagram of an rf receiver 400 using an agc according to another embodiment of the present general inventive concept the rf receiver 400 may be used in a tuner or the like to select a signal of a desired channel from a multichannel rf signal the rf receiver 400 will be described with reference to a digital tv broadcasting receiving system using an 8 vsb modulation method according to the advanced television system committee atsc standards the atsc standards were adopted by u s federal communication commission fcc in dec 24 1996 and mainly relate to compression and transmission of video and audio streams according to the atsc standards image signals are compressed with mpeg2 acoustic and voice signals are compressed with ac 3 and such signals are transmitted using a vsb transmission technique in a vsb modulation method a broadcasting signal is transmitted with a single carrier a frequency spectrum of a digital broadcasting signal using an 8 vsb transmission method is represented by a waveform shown in fig1 the rf receiver 400 includes an antenna 401 an attenuator 211 an amplifier 213 a mixer 403 an rf filter 405 and an snr adjuster 230 the snr adjuster 230 includes a first bpf 231 a second bpf 233 a first agc detector 235 a second agc detector.