( They ( ( are ( medium-range ( radio waves ) ) ) . ) )
(ROOT (S (NP (PRP They)) (VP (VBP are) (NP (JJ medium-range) (NN radio) (NNS waves))) (. .)))
They  are medium-range radio waves.
(ROOT (S (NP (NNP Am) (NN radio) (NNS waves)) (VP (VBP exist) (PRT (RP in)) (NP (DT the) (ADJP (QP (CD 540) (TO to) (CD 1600))) (NN khz) (NN frequency) (NN range))) (. .)))