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Remote Station Engineering - Communications


This page is maintained with specifications for communications equipment which are the current best-practices employed by UNAVCO in Polar Permanent GPS Station designs. Specifications are subject to change as the design evolves, however the most current design will reside here.

Technical Notes

Data Modems and Antennas

Component Photo Manufacturer Description Status
Xeos Iridium SBD/RUDICS Data Modem

Xeos Technologies

XI-100

Iridium is the only 2-way communications system with 24/7 global coverage, suited for the most remote sites where no other communications options are practical.

The Xeos XI-100 is based on the Iridium 9522B (see below), and utilizes both Iridium SBD and RUDICS services to maximize throughput and minimize power consumption. It offers TCP/IP comms to remote ethernet devices and serial communications to auxiliary sensors (e.g. met stations). An internal heater is used to warm the Iridium oscillator and achieve better cold performance than standard Iridium hardware. Xeos software runs on a server at UNAVCO and manages connections to remote sites through an internet connection (no local base modems are needed).

Average power draw is <1.0 Watt when downloading ~1MB data per day. UNAVCO has also demonstrated 10MB per day throughput (retrieving 1Hz GPS datafiles) from an antarctic GPS station.

15 units deployments in Greenland and Antarctica as of 2013.

Iridium modems must be powered using a timer switch (see below).

All Iridium modems are sensitive to antenna cable losses; keep overall cable loss between modem and antenna < 3dB.
Standard Iridium Data Modem

Xeos Technologies

9522B

Since 2005, UNAVCO has deployed standard Iridium modems using Dial-Up service in large quantities throughout the polar regions. Compared to previous generation devices, the 9522B modem delivers better cold performance and increased reliability.

The 9522B modem is offered by Iridium through its resellers, such as Xeos Technologies. Use Xeos 9522B modem with custom power / comms cable (IDC - DB9 serial - flying power leads) and SMA-TNC adapter. UNAVCO has also fielded other devices based on the 9522B board (Beam Communications RST-600 and NAL Research A3LA-X) with similar performance.

UNAVCO uses this modem with Iridium Dial-Up service, therefore local base modems are required to download GPS data. A bank of 8 base modems and associated network devices is graciously hosted by the NEON Facility in Boulder CO, to eliminate interference from Iridium transmissions on sensitive GPS systems at the UNAVCO Facility.

Average power draw is ~1.0 Watt when downloading ~1MB data per day.
Operational since 2005 with Trimble NetRS receiver. Currently deployed in 80+ locations in Antarctica and Greenland.

Iridium modems must be powered using a timer switch (see below).

All Iridium modems are sensitive to antenna cable losses; keep overall cable loss between modem and antenna < 3dB.
Iridium Antenna

Aeroantenna AT1621-142

(aka NAL Research SAF-5350A)
Quad-helix omni design, with structurally strong radome and mounting arrangement.

See Structural section for mounting adatper for aluminum pipe frame.
Stronger design than "stick" style antennas, and better performance than flat "puck" style antennas. Installed at numerous sites in Greenland an Antarctica with outstanding reliability.
Mt. Erebus Ethernet Radio Repeater Laird Technologies
SAH9-120-12
Operates in 900 MHz band using an Intuicom ethernet bridge radio modem and a rugged horizontally polarized sector antenna. Covers 120 degree swath of Transantarctic Mountains from Cape Roberts to Minna Bluff, allowing data retrieval from several remote sites to McMurdo Station and Scott Base.

In late 2012, the radio network was converted from serial to ethernet, and the power system for the radio repeater was integrated with CGPS station CONG.
Operational since 2004 at Mt. Erebus Truncated Cones site. Serves GPS stations at Cones (CONG), Mount Fleming (FLM5), and Cape Roberts (ROB4), as well as Cape Roberts Tide Gauge (operated by Land Information New Zealand).
Ethernet Bridge Radio Modem Intuicom Intuicom radio modems provide line-of-sight ethernet communications with outstanding reliability and cold performance. Used to connect remote sites with internet access points at research stations, with reliable 900MHz radio links over 100km achieved.

Average power draw is <1.0 Watt when downloading ~1MB per day.

UNAVCO has also used FreeWave radios with excellent success in polar regions.
Operational since 2004 in Antarctica. Normally deployed with Yagi antennas. Use with timer switch (below) to conserve power. Currently deployed in EarthScope PBO network, and 7 Antarctic permanent GPS stations.
Yagi Antenna PCTEL BMYD890 series 900 MHz line-of-sight serial communications, used for links to sites near research stations. Rugged welded construction. 7-element 10dB model is typical, however antenna selection is site-specific. Functional point-to-point radio link of >100 km achieved with similar Yagi antennas.

Ancillary Equipment

Component Photo Manufacturer Part Number Description Why?
Timer Switch ABB ESDR125A5P

Manufacturer specs [PDF]
Solid state 12VDC timer switch. ON/OFF duty cycle easily varied using onboard dials. 10-1000 minutes for ON cycle. 10-1000 minutes OFF cycle. Timer switches positive lead.

Use Diversitech flag disconnects FD222 and FD212, and piggyback disconnect DS22 to attach wires to timer.

Power draw is < 0.1 Watt. Timer introduces < 0.1 Volt drop in power line to Iridium modem.
Reliable timer is necessary to maintain communications with NetRS/Iridium remote stations, since Iridium modems require periodic power cycling to recover from an internal bug. This timer is also used to power cycle Freewave/Intuicom modems to conserve power. This timer replaces RS1A44/RS1A42 models that switched the negative lead.
Serial Port Surge Protector APC PS9-DTE Inline surge protector for serial communication lines. Attaches to GPS receiver serial ports, used with Iridium modems and weather station. Passive component. Mitigates serial comms problems and failures due to static buildup.
External Comms Cables Optimum Systems TNC-TNC (Iridium modem):
PPS-RF-001 revE

N-TNC (radio modem):
PPS-RF-002 revE
Coaxial cable assemblies to connect comms antenna to TNC pass-thru fitting on wall of enclosure.

Iridium modem is sensitive to antenna cable losses; keep overall cable loss between modem and antenna <3dB.
Low-loss Times Microwave LMR400 cable, 50-ohm, flexible to -40C.
Internal Comms Cables



Optimum Systems TNC-TNC (Xeos XI-100 Iridum modem):
PPS-RF-003 revE

TNC-TNC90 (Xeos 9522B Iridium modem):
PPS-RF-009 revA

N-TNC (radio modem):
PPS-RF-004 revF
Coaxial cable assemblies to connect modem to TNC pass-thru fitting on wall of enclosure. Use mil-spec RG58 50-ohm cable and quality crimp-on 50-ohm N and TNC connectors.
SMA-TNC Adapter Newark Amphenol Connex 242124 SMA-TNC adapter for 9522B Iridium modem antenna connection.
Iridium RF Surge Suppressor / Bulkhead Pass-Thru Connector Nextek QSSTFTFAU00 TNC-TNC bulkhead pass-thru device. Uses 1/4-wave technology to mitigate RF surges, passes Iridium frequencies only. Used as protection for static-sensitive Iridium hardware. This device has been very effective in reducing static-related failures of Iridium devices. Has gasket seal.

See Structural page for drawing of connector layouts on enclosures.
900 MHz Radio RF Surge Suppressor / Bulkhead Pass-Thru Connector need photo Nextek QSSTFTFAD00 TNC-TNC bulkhead pass-thru device. Uses 1/4-wave technology to mitigate RF surges, passes 900 MHz radio frequencies only. Used as static electricity protection for radio hardware. This device has been very effective in reducing static-related failures of Iridium devices, now implemented for 900 MHz radios. Has gasket seal.

See Structural page for drawing of connector layouts on enclosures.
Radio Bulkhead Pass-Thru Connector Newark Amphenol Connex 122340 TNC-TNC thru-bulkhead connector mounts to enclosure wall. For point-to-point radio comms. Has gasket seal.

See Structural page for drawing of connector layouts on enclosures.
RF Grounding Plate

B&B Machine and Grinding PPS-EN-012 revB Metal plate which mounts to wall of plastic polar enclosures. Accepts RF surge protectors for GPS antenna and up to two Iridium antennas. Connected directly to battery bank with two 10ga wires to provide ground path for static discharges. If no GPS antenna surge protector needed, can use alternate version PPS-EN-012 revA to accept N-N bulkhead pass-thru (also has one port for TNC bulkhead pass-thru or Iridium RF surge protector.

See Structural page for drawing of connector layouts on enclosures.
NF-TNCM Adapter Newark Amphenol Connex 242131 RF adapter, for converting N female to TNC male when needed.
NM-TNCF Adapter Newark Amphenol Connex 242130 RF adapter, for converting N male to TNC female when needed.
 

Last modified: 2019-12-24  02:12:28  America/Denver