An adjustable-frequency two-element bowtie antenna includes a support member on which first and second non-conductive hollow element support arms are mounted. A tip baffle bifurcates the airfoil tip into two pockets, with a first pocket being laterally open at its aft end to recover leakage flow, and a second pocket being laterally closed. The extracted signals Vs1 and Vs2 of respective frequency components are supplied to first and second window comparators.