Nolan, Marc

Replaced ISC Rack R2 90 MHz balun with modified balun. The first plot reflects the baseline noise measured using the previously used test lead, and the noise spectrum after replacement. The second plot reflects the phase shift through the original and replacement baluns. At 90 MHz the change in phase shift is apx 3.89 deg less than the phase shift through the original balun. Attachments 3-5 show the modifications to the balun. An N-SMA adapter has replaced the original male N-type connector, and a copper end plate has replaced the PCB end cap. The transformer is moved and a UMCC connector is placed on the board. A coax (RG-174) SMA-UMCC line replaces the unshielded lines originally in the Balun. Capacitors are added to the female end of the balun (apx 300 uF). Attachments 6 and 7 reflect the noise change as measured from an antenna placed in the rack ( apx 15 dB change in radiated Noise).