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GPS Antenna Cover Tests:
Determining Signal Loss and/or Shift in Different Types of Antenna Covers

by J. E. Galetzka and K. W. Hudnut
(last update 8/7/96)

In early summer '96 we conducted tests on five different types of antenna covers--or 'radomes'--that we use on continuous GPS sites in the Los Angeles area GPS array. The tests were designed to look for signal loss and/or shift caused by physical properties (i.e. material, shape) of various antenna covers which would yield inaccurate position data generated by continuous GPS sites.

Index:
Sites Selected:Station observation logs, photos, and raw data
Test Setup:Short baselines with cover on/off
Test Results
Lessons Learned
Acknowledgements

Sites Selected: Station observation logs, photos, and raw data

Holcomb Ridge

Chilao USFS Fire Station

Claremont Biological Field Station

Table Mountain Facility, CA

Mt. Lee

Test Setup: Short baselines with cover on/off

A temporary GPS remote station was setup over a fixed reference mark located within 20 meters of the permanent contiuous GPS station to be tested. The remote station consisted of:

The remote station tracked continuously for six hours: the first three hours with the antenna cover of the permanent GPS station ON; the last three hours with the antenna cover OFF. Data logged over the six hour test period was extracted back at the office using a laptop PC running Trimble Remote Control 2.01 for later processing.

The reference marks, ovr which the remote station was setup, consisted of pre-existing markers (i.e. gravity station, county benchmarks) or new markers installed for the purpose of the tests.

Antenna slant height (SH) was measured from the center mark on the reference mark to the lower outside edge of the antenna choke-ring using an Ashtech Measuring Rod. The antenna slant height was taken at three points around the antenna before and after the test to insure that the remote station had not moved.

Test Results

Lessons Learned

Acknowledgments

We would like to thank Tony Grissim and Trimble Navigation Ltd. for allowing us to borrow a 4000SSi Receiver, Dorne-Margolin Choke-Ring Antenna, power supply, download software and cables.

This report is preliminary and has not been reviewed for conformity with U. S. Geological Survey editorial standards. Any use of trade, product, or firm names is for descriptive use only and does not imply endorsement by the U. S. Government.

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