The 430 MHz Transmitter

The 430 MHz radar transmitter at Arecibo Observatory was built in 1962 by Levinthal Electronic Products, which became Radiation at Stanford, as original equipment for the observatory. The transmitter operates at a fixed center frequency of 430 MHz with a maximum transmitted bandwidth of 1 MHz. Two Litton L-3403 or L-5773 klystrons operate in parallel as a balanced amplifier, with a 90-degree power splitter at the input and a high-power 90-degree combiner at the output, to provide a maximum total peak pulse output power of 2.5 MW. Power is delivered to the antenna platform cia 1,500 Ft. of WR21000 waveguide. Am infinitely variable power splitter on the platform provides transmitter power to feed antennas in both the Gregorian dome (a feed horn) and the carriage house (the line feed). This allows dual beam operation, which could have been called "dual radar" operation, as it is equivalent to two radars pointing in different directions. The maximum duty cycle is 6% so the maximum average output power is 150 kW.