Scatter from man-made, field-aligned, F-layer irregularities offers a means of over-the-horizon communication at VHF frequencies. Experimental data collected in 44 days of field operation in the autumns of 1972 and 1973 defines representative characteristics of signals transmitted over such a scatter circuit. A cloud of field-aligned scatterers was created by the Platteville, Colorado, ionospheric modification facility; test transmitting sites were established in Texas and receiving sites in California. The data describe mean and peak cloud radar cross section, the dependence of cross section on heater power, heater modulation, time of day, and signal frequency, the circuit coherent and incoherent bandwidths, the signal amplitude statistics and spatial correlation, and the signal spectral spreading. The experiment also included the transmission of representative types of modulated signals including SSB voice, 100-word/min FSK teleprinter data, 2400-bit/sec data, 30-kHz FM voice, and 3-kHz FSK facsimile.