Rohde schwarz hm8021 4 universal frequency counter rohde schwarz 3593 0780k02 p the rohde amp schwarz hm8021 4 is a universal frequency counter that leads the market in high performance low price counters this microprocessor based instrument has a built in self test as well as two high sensitivity inputs with an extended frequency range from 0hz to 1 6ghz p p the reciprocal frequency measurement technique provides high resolution of low frequency signals with at least seven signi