1.Malachite, prefilter, balances the design of the allmetal aluminum housing malachite radio without prefilter and reduces interference in frequency bands such as midwave and shortwave FM broadcasts. 2.4in1 filter: all popular receivers, radios, SDRs and malachite can be used together. 3.In addition to the use of 40 meter amateur frequency bands, the P3 filter is 1230 MHz, which is the use of shortwave high frequency bands as well as the use of 20 meter, 15 meter, and 10 meter amateur frequency bands. The P4 filter is an FM radio frequency of 88108 MHz. The fourinone filter can be used with an active onetofour splitter to provide prefilter functions for SDRs, radios and receivers. 4.This product contains four sets of independent bandpass filters. The filters are divided into 4 frequency bands. The P1 filter has a frequency of 0.51.5MHz, which is suitable for listening to midwave radio. The P2 filter is 4.512MHz, which is suitable for shortwave and low frequency bands.