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GPS INSTALLATIONS


There are several GPS systems in use for Seismology purposes at "Realfagbygget". Some are temporary, for testing purposes, others are more permanent. The latter type is documented here.

1 NEW GPS ANTENNAS INSTALLED ON TOP OF "SCIENCE BUILDING" FEB. 2017 ...?


In February 2017 we consider installing GPS antennas on top of Science Building (Allé gt. 41), with a completely new cable routing inside building.

Preliminary specifications. Can be changed, if GPS signal distribution system used, or signal splitters.

  1. 1 ea for EPOS-N standard digitizer, the Nanometrics Centaur, using RFS Mod. "LCF12-50J" coax cable
  2. 1 ea for Trimble NetR9 Geodetic GNSS Receiver, also using RFS Mod. "LCF12-50J" coax cable
  3. 2 ea Güralp GPS (for DM24 and DM24-EAM digitizers), using RS-232 cable.

1.1 Relocating BER digitizer


BER digitzer (Güralp DM24-EAM) is currently placed inside alcove of Seismo-lab. When re-routing GPS cables, digitizer can be moved to a location, adjacent to STS-2 sensor under metal dome. Digitizer, with new AC/DC-converter and GPS cable terminals, can be mounted inside this enclosure:

1.2 Required cable length


  a) Inside Seismo-lab, to door (ceiling) ...................:                14   meter (floor-ceiling: 3.2 meter)
  b) From outside Seismo-lab to bottom of cable ladder ......: 20 + 20 +13  = 53   meter
  c) Floor of basement to 3rd level (rail height) ...........:                15,4 meter
  d) 3rd level (rail height) to 5th level (rail height) .....: 3 + 3        =  6   meter
  e) 5th floor (rail height) to roof ........................:                 3   meter
  f) Routing to antenna mast ................................:                 3   meter
  --------------------------------------------------------------------------------------
     In total ...............................................:                94,4 meter
                                                                              ==========                                                             

1.3 Coax cables


1.3.1 Max attenuation permitted at highest GNSS frequency


This concerns requirement for Trimble NetR9 geodetic GNSS receiver:

According to NetR9 specifications, the receiver can withstand a loss of 12 dB between antenna and receiver. This is the sum of coaxial cable attenuation, and connector insertion losses, which is typically 0.15 dB max at 10 GHz (ref Amphenol N-connector data sheet).

Information from Trimble NetR9 User Manual, p. 28:

On p. 76 in Trimble NetR9 User Manual (http://trl.trimble.com/docushare/dsweb/Get/Document-495804/NetR9_UserGuide_13506.pdf) there is a list of GNSS signals that are used:

Trimble NetR9 GNSS signals Comment
GPS: L1 C/A, L2C, L2E (Trimble method for tracking L2P), L5 Highest frequency: "L1" = 1575,42 MHz
GLONASS: L1 C/A and unencrypted P code, L2 C/A1 and unencrypted P code Highest frequency: "L1OF, L1SF" = 1602 + n×0.5625 MHz, max n=+6, which yields 1605.375 MHz
Galileo GIOVE-A and GIOVE-B "GIOVE A was retired (but not decommissioned) in June 2012" (Source: Wikipedia, on GIOVE). GIOVE-B launched in 2008 - also related to test of Galileo concept -- it's assumed these satellites are not used anymore (?)
SBAS: L1 C/A, L5 supporting WAAS, EGNOS and MSAS As for GPS mentioned above: Max frequency is "L1" = 1575,42 MHz
L-Band OmniSTAR VBS, HP and XP Looks to be SBAS (= "satellite-based augmentation system") that requires subscription (that we are not using)

The coax cable we want to use, LCF12-50J, has 9.61 dB/100 meter attenuation at 1700 MHz. If four connectors are used, each with 0.15 dB insertion loss, that will be 0.6 dB in addtion - in total, 10.2 dB loss. Requirement is thus fulfilled with nearly 2 dB margin. This coax cable is most likely among the top in Ø15mm segment.

1.3.2 List of coax cables. Typical N-connector insertion loss.


Coax type Attenuation @ 1500 MHz
GPS L1 = 1575,42 MHz
[dB/100m]
Outer cable diameter Min bending radius
(Installation / repeated)
Manufacturer Link to datasheet Supplier
LCF12-50J 8.97 Ø15.8mm 70mm / 125mm RFS - Radio Frequency Systems PDF Jørgen Holmefjord AS
LMR-600 10.9 Ø14.99mm 38.1mm / x Times Microwave PDF
Ecoflex 15 plus 11.4 Ø14.6mm SSB PDF Holund

Typical N-connector insertion loss is 0.15dB @ 10 GHz - ref Amphenol N-connector data sheet.

1.4 Ethernet cable


1.5 El. entrepeneurs


1.6 Misc - antenna mast equipment


1.7 GPS Repeater / Re-radiation kit


Credit B.O.R./GEO-UiB for this information.

Manufacturers

Click to visit L1/L2GHNRRKIT product page.

GPS Re-radiating kit model "L1/L2GHNRRKIT" from GPS Networking. Click to visit product page.

1.8 GPS signal splitter


Standard splitters - product line of "GPS Networking": https://www.gpsnetworking.com/product-categories/standard-splitters

Click to see product specifications.
ALDCBS 1 X8 Amplified 1x8 GPS Splitter from http://www.gpsnetworking.com -- Click to see product specifications.

Credit R.H./Kartverket for this information.

1.9 Antenna mast details - possible suppliers


1.10 Cable routing inside Science Building


From room KF18A "Seismometer" in basement, to elevator housing on roof:

2 GPS ANTENNAS, ON SOUTH-FACING FACADE OF ALLÉ GT. 41


Two Güralp GPS units are mounted on south-facing side of Allé gt. 41 (Science building) One is feeding timing signals to BER station (STS-2) digitizer. The other is used for test purposes.

2.1 Güralp GPS pin-out


The Güralp GPS unit is used with Güralp CMG-DM24 digitizer.


Wiring details for the compatible socket, ***-12-10S, as seen from the cable end.

2.2 Photos


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Page last modified on May 14, 2019, at 11:22 AM
Electronics workshop
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