One of the first large mast radiators was the experimental tubular mast erected in 1906 by Reginald Fessenden for his spark gap transmitter at Brant Rock, Massachusetts with which he made the first two-way transatlantic transmission, communicating with an identical station in Machrihanish, Scotland. However during the radiotelegraphy era before 1920 most long distance radio stations transmitted in the longwave band, which limited the vertical height of the radiator to much less than a quarter wavelength, so the antenna was electrically short and had low radiation resistance from 5 to 30 ohms. Therefore most transmitters used capacitively toploaded antennas like the umbrella antenna or inverted L and T antenna to increase the power radiated. During this era, the operation of antennas was little understood, and designs were based on trial and error and half-understood rules of thumb.