On November 18, 1943 the first public demonstration of electronic television via airwaves in Uruguay was performed by the pioneer tecnician and experimenter Mario Giampietro. The authorized callsign was CX5AQ. This was the first radio television broadcast of this type in Uruguay and reportedly in South America, 112 to 138 Megacycles (2.50 m). The antenna was a double colinear Zeppelin installed at his home and the receiver and portable antenna was at the Palacio Legislativo del Uruguay (the Parliament building), in Montevideo.

From a RCA Bulletin of that year:

Mr. Giampietro based the design of his home-built equipment on diagrams or plans published by RCA before the outbreak of the current international conflict. However, he has had to introduce ingenious changes in some details, due to several technical differences. For example, the scanning system, which the National Broadcasting Company based on 60-cycle circuits, had to be modified to adapt it to the 50-cycle current used in Montevideo.

The scanning system currently used by this technician allows him to transmit outdoor scenes of 440 lines, although it is true that indoor images have generally been limited to 220 lines. In one of his experiments, he used fluorescent tubes to illuminate night scenes. These fluorescent tubes gave satisfactory results, according to Mr. Giampietro, despite their limited intensity.

This young technician, employed by the Uruguayan Congress, is now using 115 megacycles, but his experimental station will soon change, it has been announced, to a commercial wavelength of 52 megacycles. The young man claims that his images, transmitted from an antenna located only 60 feet (18 meters) above street level, have been captured with absolute precision by amateurs who were located at a distance of more than two kilometers. Blocked on one side by large buildings in the vicinity, the signals can only be captured by the south side of the transmitter - according to this technician.

Here are some additional details from the text:

Mr. Giampietro is a young and innovative technician who has made significant progress in building an experimental television in Uruguay.

His experiments with different scanning and lighting techniques are an example of his creativity and tenacity.

The change to a commercial frequency will allow for greater dissemination of his work and will contribute to the development of television in Uruguay.