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Reports until 14:34, Tuesday 17 July 2018
nolan.king@LIGO.ORG - posted 14:34, Tuesday 17 July 2018 (42940)
ISC Rack 1 - 71 MHz BALUN diagnosis/replacement.
Nolan, Marc, Dick

Replaced ISC Rack R1 71 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. Signal strength is attenuated by aprx 44 dBm. The second plot reflects the phase shift through the replacement balun. At 71 MHz the change in phase shift is apx 23 deg phase shift. 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 3 and 4 reflect the noise change as measured from an antenna placed in the rack ( apx 10 dB change in radiated Noise). For pictures of modified balun and test lead refer to ISC Rack 1 - 118 MHz BALUN Alog entry. 
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