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This paper describes developed learning objects (or simulators) to aid in the an-tenna design teaching at an engineering technology level. An important motivation for the development of learning objects is to allow a quality and adapted teaching for Brazilian Uni-versities, in a free form, without spending with an expensive commercial software. The numerical methods are often used to compute important parameters of antennas. An essential parameter of any antenna is the three-dimensional (3D) radiation pattern. With the computa-tion of this 3D radiation pattern is possible to calculate other parameters as directivity, half-power angle, beam efficiency, levels of side lobes, and so on. Thus, an important aid in design of antennas is the visualization of 3D radiation patterns. A few learning objects was developed making use of the OpenGL graphics library to allow the visualization of three-dimensional radiation patterns of the following kinds of antennas: arrays of isotropic anten-nas, dipole antennas in free space and presence of perfect ground plane, and Yagi-Uda an-tennas. Other more adequate graphics software named Visualization Toolkit (VTK) has been used in the development of 3D simulators for antenna radiation patterns. VTK is an open-source, object-oriented software for computer graphics, visualization and image processing. Although it is large and complex, VTK is easy to be used once learned its basic object-oriented design and implementation methodology. VTK is a library of C++ classes. Neverthe-less, application developers may use interpreted languages Tcl, Python and Java. In this pa-per it was used Python and wxPython, a cross platform toolkit, for graphical user interface creation. The wxPython is a wrapper around wxWidgets, which is a mature cross platform C++ library. One of the objectives in use Python, wxPython and VTK is to allow fast devel-opment of scientific visualization prototypes. The second objective is to work with object-oriented design and to transform easily programs in Python (with wxPython and VTK) for programs in C++ (with wxWidgets and VTK). The last objective is to build large and complex applications of scientific visualization, which will be portable, fast and without cost for the students.