Project: TBASErdn021209 Roger Norrod Trying to isolate cause of "8 minute" cycling of total power first seen on 11/13/2002, project TRDN11_13_02. Setup initially using IF Rack noise source. Using ODM 2, 6, 8 (4 out of service). Equipment Room connections: OR CM SF DCR CH 2 1 1 9 2 2 2 10 6 11 3 11 6 12 4 12 8 15 7 15 8 16 8 16 DCR mode TPnoCal, tau=1s, T=300s. Recording all 16 chans. BW 200MHz in SF modules, 320MHz in IF Rack. G1-G7 set to 12600 MHz. Scan 1-6: Figure 1, 2, and 3. Channel 2 IF excessive short-term instability. All equipment room detectors show the 8 minute cycling at level of about 0.3% p-p. The SF7 and 8 TP experienced a step in total power of about 0.4% (SF7) and 0.1% (SF8) at sample ~450. Injected lab noise source into CM1, 5, 11, and 15. Changed G1 and G7 to 10700 MHz (because noise source works only to 1.5 GHz), and changed attenuators in CM1, 5, 11, and 15 to rebalance. Scans 7-12: Figures 4, 5, and 6. Figure 4, compared with Figure 1, indicates there is instability introduced in IF Channel 2 between the ODM2 detector and the OR 2 outputs. But, the channels coming from the IF Rack noise source (SF2, 4, and 8) show approximately the same 8 minute ripple as those coming from the equipment room noise source (SF 1, 3, and 7). This means the 8 minute cycling is introducted within the Equipment Room. Moved lab noise source to J3 inputs of SF1, 3, 5, and 7. Source was off for several minutes, so expect some initial drift. Scans 13-18: Figures 7, 8, and 9. It is clear that most of the 8 minute cycling is introduced in the Converter Racks, but it is also seen at ~0.1% p-p level in the AF rack equipment (or in the lab noise source output). We began to consider common factors, and the most obvious is temperature. Sure enough, the room temperature was found to be cycling ~1.5F p-p with about an 8 minute period. The HVAC proportional controller is having difficulity holding the set-point of 60F, reason as yet unknown.