The possibilities to use electric antennae made of two small spheres to study the velocity distribution of charged dust grains in space are shortly examined in this paper. The electric potential difference ΔΦ between the two spheres is determined by solving the Poisson's equation in a dusty plasma and several examples of "waveforms" (ΔΦ as a function of time t) are shown as illustration. Typical are for dust grains of radius of 100 microns, signals of the order of 500 microvolts are produced. The limitations due (i) to the anntenna (the discharge time must be smaller than the characteristic time of the signal) and (ii) to the plasma (noise due to a large number of plasma particles) are also examined. A table summarizes the results in different conditions. We come to the conclusion that with a system of antennae it is possible to detect (especially near comets and planetary ionospheres) dusts in view to determine their velocity characteristics.