Application Form [pdf]

This document pretains to SES-LIC-INTR2018-04088 for License on a Satellite Earth Station filing.

IBFS_SESLICINTR201804088_1468424

MICROWAVE PATH SURVEY REPORT RADIO FREQUENCY INTERFERENCE (RFI) MEASUREMENT REPORT Prepared For ViaSat West Bridgewater (Boston), Massachusetts Transmit and Receive Earth Station 17-21 GHz and 27-31 GHz JANUARY 31, 2018 19700 Janelia Farm Boulevard. - Ashburn, Virginia 20147, USA - 703.726.5500 - Fax 703.726.5597

TABLE OF CONTENTS SECTION 1 Introduction and Background 1.1 Introduction 1.2 Background 1.3 Constraints SECTION 2 Test Procedure 2.1 Calibration 2.2 Methodology SECTION 3 Data Presentation SECTION 4 Summary of Results SECTION 5 Conclusions and Recommendations 5.1 Conclusions 5.2 Recommendations Addendum 1 Addendum applicable to this report showing spectral plots for one possible interference case as identified in the office study.

SECTION ONE

SECTION 1 INTRODUCTION AND BACKGROUND 1.1 Introduction On-site Radio Frequency Interference (RFI) measurements were performed on behalf of ViaSat, Inc. on JANUARY 31, 2018 at their proposed site in West Bridgewater (Boston) Massachusetts. The purpose of these measurements was to determine the relative RFI levels in the 17-21 and 27-31 GHz common carrier frequency band and their impact on digital down-link satellite reception. Measurements were performed at one designated location. The purpose of this report is to document the results of these measurements and to present recommendations. The analysis in this report is based upon the following: • Andrew 4.1 Meter Antenna • Satellite Arc: 55 to 115 Degrees West Longitude • Frequency Range Considered: 17 to 21 GHz and 27-31 GHz • Interference Objective: -156 dBW/1 MHz • Type of Reception: Digital • Measured Antenna Center Line: 6.5 Feet Above Ground Level 1.2 Background ViaSat, Inc is proposing to locate a new transmit/receive antenna at an existing location of 420 1’ 46.6” N and 710 0’ 26.4” W ViaSat, Inc had requested that Comsearch conduct RFI measurements at the facility to assess the interference potential. This facility is currently nonoperational and measurements were done at a point near the proposed antenna locations. The measured site is identified on a portion of a topographic map shown in Figure 1.2-1. An aerial photo of the site location is shown in Figure 1.2-2. A photo of the measurement using a GPS is shown in Figure 1.2-3.

1.3 Constraints The analysis in this report is based upon the following assumptions and constraints. • The antenna selected will conform to the FCC reference pattern 32-25 Log as specified in 47CFR 25.209(a)(2). • It is assumed that during the measurement period all of the terrestrial transmitters were active and operating at full transmit power for the licensed frequencies unless otherwise noted. • The signal identification and frequencies analyzed are based upon information obtained from the various common carriers as to what frequencies were active at the time of the measurements and the traffic these frequencies were supposed to be carrying. • The actual ground elevation of the site is based on the data from the topographic map. • The interference objective of –156 dBW/1 MHz used throughout this report is based upon estimated link budget parameters and is subject to change. ViaSat, Inc should review the system parameters for this down-link in order to verify the viability of this objective.

Figure 1.2-1 – Topographic Map

Figure 1.2-2 – Aerial Photograph

Figure 1.2-3 – GPS Photograph

SECTION TWO

SECTION 2 TEST PROCEDURE 2.1 Calibration Figures 2.1-1 is the block diagram of the test set for all bands to be tested. All test equipment used was allowed a proper warm-up period prior to calibration. The test set was calibrated by the signal substitution method, as recommended by NSMA, utilizing a synthesized signal generator. The reference signal from the signal generator was adjusted for the center frequency of each band to be tested and measured with a thermal power meter for calibrated reference test level (-60 dBm). This calibrated reference signal from the signal generator was then injected into the end of the coaxial cable of the test set at the point, which normally connects to the test antenna. A spectrum analyzer then measured the reference test signal level after passing through the test set. At this point, the spectrum analyzer was calibrated such that the top graticule of the spectrum analyzer display (-60 dBm) corresponded to the injected reference signal (-60 dBm) by utilizing the reference level offset function of the Anritsu –M52720T spectrum analyzer. Upon completion of the calibration process, a known reference level was obtained for the measurements that correspond to a given set of spectrum analyzer display readings. The following formula is used to transform the measured signal level as read on the spectrum analyzer display (dBm) to an isotropic reference signal level (dBWI) as seen at the point of test: dBWI = LI - GA - 30 Where: dBWI = Isotropic level in dBW LI = Level (dBm) of injected signal GA = Test antenna gain -30 = Conversion factor from dBm to dBW at 19.5 GHz: dBWI = -60 dBm - 30 dB - 30 dB = -120 dBWI In this instance, the spectrum analyzer displayed measured signal level of –60 dBm equates to an isotropic signal level of –120 dBWI. Figures 2.1-2(A-H) displays the spectrum photographs of the described calibration procedure employed during these measurement.

Figure 2.1-1 Receive Test Equipment Block Diagram

Figure 2.1-2 (A) Calibration Spectrum Photo 17.5 GHz Figure 2.1-2 (B) Calibration Spectrum Photo 18.5 GHz

Figure 2.1-2 (C) Calibration Spectrum Photo 19.5 GHz Figure 2.1-2 (D) Calibration Spectrum Photo 20.5 GHz

Figure 2.1-2 (E) Calibration Spectrum Photo 27.5 GHz Figure 2.1-2 (F) Calibration Spectrum Photo 28.5 GHz

Figure 2.1-2 (G) Calibration Spectrum Photo 29.5 GHz Figure 2.1-2 (H) Calibration Spectrum Photo 30.5 GHz

2.2 Methodology Upon arriving at the existing earth station site, azimuth and horizon elevation measurements were performed to evaluate if any satellite arc obstructions exist. The coordinates of the existing earth station site were verified on the DeLorme topographic map. Photographs were taken to document the satellite arc (clearance) and are included in this report. After site coordinates and horizon elevations were verified, the test equipment was set up and calibrated to measure the RF environment. Measurements were conducted at the proposed earth station location for the 17-21 and 27-31 GHz band. After the equipment calibration was completed, the test antenna was mounted on an extendable tower and elevated to a height of 6.5 feet. This height is greater than the centerline of the earth station antenna. The antenna was rotated 360 degrees (scanning), once in each polarization, while activating the peak hold function of the spectrum analyzer. This enabled the analyzer to maintain and display the maximum signal level received for all frequencies under consideration. After the initial documentation of interference, all interference conflicts if observed were peaked on to determine the azimuth and the level of the interference source. Upon completion of the RF testing, the measured signal levels were transposed to earth station interference levels after accounting for the addition of the corresponding earth station antenna gain.

SECTION THREE

SECTION 3 DATA PRESENTATION The following section contains the tables and spectrum photos pertaining to the site location measured. 3.1 West Bridgewater (Boston) Massachusets - Table 3.1-1 presents a site data sheet including all pertinent site information. - Figures 3.1-1 and 3.1-2 are the photographs depicting the existing earth station site and satellite arc. - Figures 3.1-3 through 3.1-10 are the RF spectrum photographs depicting the interference environment at the test site.


Document Created: 2019-04-05 10:27:56
Document Modified: 2019-04-05 10:27:56
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