The Potential to Receive Direct Satellite Broadcasting at Home
Satellite broadcasting requires a small antenna and a high-sensitivity receiver, in addition to the actual broadcasting satellite. Conventional satellite communications prior to this period had employed low-power satellites, necessitating the installation of receiving antennas ranging in size from several to dozens of meters in diameter. These were too large for home use. For this reason, the reception of satellite broadcasting at home required a low-price, high-sensitivity receiver, together with an increase in the satellite’s output. STRL devised a planar circuit mounted in a waveguide to create a receiver that could utilize a small, low-price, yet high-sensitivity antenna.

Path to Implementation
After various preparatory work had been completed, channel assignment, receivers, etc., Japan’s first broadcasting satellite (BS) was launched atop a U.S. Delta Rocket on April 8, 1978. This allowed numerous satellite experiments to be conducted.
In 1979, the decision was made to launch two satellites (BS-2a, BS-2b), allowing backup satellites to carry out practical broadcasting on two channels. These were launched by domestically manufactured N-2 rockets.
In order to extend its usable life, while maintaining the same scale as the BS satellite, these new satellites switched from the coupled-cavity type TWT used in the BS satellite to a helix type, reducing the weight to half that of the TWT in the BS satellite. After integrating the experimental results obtained by the BS satellite, BS-2a was launched from Tanegashima Island in January 1984.
Unfortunately, two of the TWTs on the satellite failed within several months of the launch, so the scheduled satellite broadcasting had to be hastily adjusted to test broadcasting on a single channel. Immediately, investigations were made to isolate the cause of the TWT failure and to create countermeasures. Using BS-2b, which had been launched in February 1986, regular satellite broadcasting commenced on two channels after a test broadcasting period.
The experience obtained through the BS-2a satellite program was later put to good use in ground-based space environment tests on TWTs, resulting in domestic TWTs being installed in BS-3a and BS-3b, which were launched in 1990 and 1991, respectively.
Thirty-six years later, responsibility for broadcasting satellite research, which was initiated at STRL in 1966, was transferred to the Broadcasting Satellite System Corporation. Currently, the broadcasting satellites BSAT-1a and 1b, as well as the digital broadcasting satellite BSAT-2a, provide satellite broadcasting services to over 16 million households.

1. Appearance of new media
2. Digitization of sound