  We present an experimental and analytical study of resonances in the
current-voltage characteristics of single and double row triangular Josephson
arrays. The magnetic field dependences of the voltage positions of the
resonances have been measured for various cell inductances and junction
critical currents. In double row arrays, we have observed a peculiar resonance,
whose voltage position decreases with magnetic field. We derive the spectrum of
linear electromagnetic waves propagating in the arrays. In the double row
array, the spectrum consists of many branches that differ by the behavior of
the Josephson junctions transverse to the bias current direction. The measured
magnetic field dependence of the resonance voltages is mapped to the linear
mode spectrum and good agreement between experiments and model is found.
