To: Edgar Castro

From: Jon Hagen

Date: 4-8-99

Subject: Monthly report for Mar. '99

The second over-speed limiter (emergency brake trigger) was installed on the carriage house. A guard is being made for its leaf spring which was vulnerable to accidental damage by platform workers. The limiter for the Gregorian has been working for many weeks. Converters from RS422 to RS232 has been added in the control room so that the operations computer can monitor the status of both limiters.

Work to fully re-document the 430 transmitter is nearly complete and is now at the stage of properly documenting the many modifications made to the transmitter during its three decades of operation. As obsolete modifications are found, they are being removed. The 20-year old timing generator will be replaced with a new design that will be simpler and more reliable. The final step in this project will be to make functional checks of every subsystem (monitoring, protection, etc.) and re-calibrate the various metering circuits.

Development of a compact turnstile for transmitting from the Gregorian dome will be done at Arecibo, using an S-band model to be built at the Ithaca lab. Tentative plans are for a light- weight half-height turnstile with waveguide-to-coax transitions in each arm.

I hope to devote time in April to the problems of the tie-down drive system and on the collaboration with Bill Sisk on the tertiary drive system.