To: Edgar Castro

From: Jon Hagen

Date: Mar.. 2, 2001

Subject: Report for February, 2001

Drew detailed schematic and layout drawings for the additional 7-pole 125 kHz active lowpass filters needed for the 430 Gregorian radar system (original R671 documentation had been lost). Found errors in component values in the old as-built filters. Made and ran a Spice model of the filter and found that the original filters could not have worked as intended, due to bandwidth limitation of the LF347 op amps. Nevertheless, Mike Sulzer has been happy with the old

filters and wants us to duplicate them. In any event, they will all be replaced by digital filters within the next five years.

Checked the tuning of the old collector, used for 430 transmitting from the Gregorian, after cleaning RTV off the flange of the access port cover plate. The return loss was observed to be -22 dB which was deemed acceptable. Nevertheless, reflection measurements made at the platform from just past the rotary joint down into the Gregorian showed a return loss of only some 15 dB. The source of the additional reflection must be identified and corrected.

We need two more half-height waveguide-to-coax transitions for general testing. These units can be made from a spare section of waveguide we have on hand. The section can be sawed in half and have plates welded on the open ends and suitable probes or loops would be installed. A provisional transition was, using a back plate fitted with a type-N connector and wire loop. This plate bolts to another short section of half-height waveguide to make a transition with better than 25 dB return loss.

I have had some discussions with Bill Sisk regarding the design of the regeneration cards used in the Vertex system. Andy Dowd began a project to design a more reliable card. Bill is carrying on with that project

Considerable effort was spent preparing for the visit of Klaus Wilmeroth from Vertex. I have the spare PLC running in the spare crate and have written a PLC demonstration program (that

blinks the lights on the spare digital output card). I have been able to burn this program

onto a ROM card. I am now doing the same with the spare LCU card: getting it to run in the spare crate and putting its program development system on the PC dedicated to supporting the

Vertex system C compiler, loaders, editors, etc).

A mass storage unit, containing a floppy drive and a hard drive, was ordered from Siemens, as well as a manual for the spare LCU (which is not the same model as the original LCU). It was originally thought that the LCU would run from its built-in 'silicon disk' so that one storage unit would be needed. The difficulties we've had in integrating the spares make it necessary for the spare LCU to be identical to the working LCU, i.e. to have its own mass storage unit. The NiCd backup batteries in the time-code readers for this system are exhausted and must be replaced. These efforts are being made so that Klaus will have all the tools necessary to leave us set up a complete set of working spare modules.