EPOS-N - European Plate Observing System
Seismometers / vault construction
Stations: Upgrade/install notes
Ideas for improvements
Installation / Inventory
Last update: February 17, 2020, at 01:26 PM
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.
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.
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:
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 ==========
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:
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.
Typical N-connector insertion loss is 0.15dB @ 10 GHz - ref Amphenol N-connector data sheet.
Credit B.O.R./GEO-UiB for this information.
GPS Re-radiating kit model "L1/L2GHNRRKIT" from GPS Networking. Click to visit product page.
Standard splitters - product line of "GPS Networking": https://www.gpsnetworking.com/product-categories/standard-splitters
ALDCBS 1 X8 Amplified 1x8 GPS Splitter from http://www.gpsnetworking.com -- Click to see product specifications.
Credit R.H./Kartverket for this information.
From room KF18A "Seismometer" in basement, to elevator housing on roof:
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.
The Güralp GPS unit is used with Güralp CMG-DM24 digitizer.