[IGSSTATION-4610] BRMU new antenna and cable

Giovanni Sella Giovanni.Sella at noaa.gov
Wed Oct 5 13:20:03 PDT 2011


Author: Giovanni Sella

Dear Colleagues,
  The antenna and cable for station BRMU were replaced on 27 October 
2011 with a new JAVRINGANT_DM and a new LMR-600 cable with a lightning 
arrestor.
   The old antenna was found without a radome, contrary to the site log, 
and no conclusive information could be obtained from onsite staff (2 
have retired over a year ago) as to whether a radome was ever installed 
or was later removed/lost. The old antenna was also found to be oriented 
180 degrees off from True North. The antenna cable consisted of a 6m 
section of LMR-400 followed by 20+ meters of RG213 antenna cable. The 
rubber gasket at the end of the LMR-400 cable which attached to the 
antenna connector was partially unstuck, possibly allowing moisture to 
enter the cable. The connection between the LMR-400 and RG-213 was 
solidly wrapped in butyl tape. The other end of the RG213, at the 
receiver, also had the the rubber gasket on the connector unstuck and 
with the cable possibly partially loose at the connector.
  The antenna mount lacks a force centering device, being a threaded 
rod. It had two washers, one a thick split washer and a second thin 
normal washer. When the new antenna was installed it could not be 
oriented to True North using these washers. I was able to find a new 
thicker split washer that allowed the antenna to be tightened down very 
firmly and aligned to true north. The difference in thickness between 
the two washers vs one washer <1mm. The antenna was and is not perfectly 
level with a small downward tilt to the North, indicating that the 
threaded rod is not plumb.
  After extensive internal and external discussion we have decided to 
leave the UNAV radome in the site log for section 4.2 as all information 
that we have to date is that the radome was installed and later lost.
  A revised site log has been submitted to the IGSCB.
  Data will be flowing shortly with back data to day 271. Updated 
pictures will be available at NGS and submitted to IGS in the next 
couple of days.
  Have a pleasant day/night.
  Giovanni




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