1FOUR IN ONE FILTER: All hot receivers, radios, SDR can be used together, very practical and versatile, provide great convenience for your life and work 2MULTIPLE FREQUENCY BANDS: Contains four sets of independent bandpass filters, the filter is divided into four frequency bands, P1 filter is 0.51.5MHz, meet the medium wave radio listening use, P2 filter is 4.512MHz, meet the short wave low band, and 40 meters amateur band use, P3 filter is 1230MHz, meet the short wave high band use, and 20 meters, 15 meters, 10 meters amateur band used, P4 filter for FM broadcast frequency of 88108MHz 3PRE FILTER: The 4 in 1 filter can be used with a one quarter active distributor, which can provide pre filter functions for SDR, radio, and receiver, very versatile 4INTERFERENCE RESISTANT: SDR, pre filter, make up for the all metal aluminum shell malachite radio without a pre filter design, can reduce the interference of medium wave short wave FM broadcast and other frequency bands, can achieve multi channel multi frequency reception 5DURABLE MATERIAL: Prefilter LC passive filter adopt alloy steel material, possess high strength, high toughness, wear resistance, corrosion resistance, high and low temperature resistance, non magnetic