With no formal training program for us Newbies, we either learned operation and maintenance from the preceeding people or plowed into the manuals. Not many of the guys dug deeply into the theory and inner workings of the System. Somehow, I found the mysteries irresistable. Darell Hartung provided me with a number of technical sessions with the manuals, the 545 scope and Darell’s notes. Fortunately, he saved them and some are reproduced here.

MOD I and MOD III were different in many ways, but the basics were the same. Ultimately, the Range Counter was eliminated and the Harris/Burroughs computers calculated Range and Rate as well. Azimuth and Elevation continued to be derived directly from the encoders, Nordens on MOD I and Baldwins on MOD III. For accurate encoder data, it was crucial that the antenna be pointed at the transponder to the accuracy needed. This pointing was attained by processing return pulses from the transponder and deriving Azimuth and Elevation error from them. A tuned up system was capable of angle error in the range of .002 degrees or less.

Angle error was always a difficult subject with the processing taking place in the microwave plumbing. To make it simple, Elevation was deterimined by the difference between pulse height of the two feedhorn channels. Azimuth by comparing the phase.

Here are Darell’s notes:

LtoR: Range Counter / Elevation Error Block Diagram / Elevation Plumbing

LtoR: Elevation Derivation pg1 / Elevation Derivation pg2

LtoR: MOD I Servo / Norden Encoder