Pointers when using Iridium Service

Providing quality service to users around the world, the Iridium satellite system is monitored for call performance from numerous locations 24 hours a day, 7 days a week. The Iridium Satellite Network consistently provides reliable signal strength for users globally.

Iridium continually strives to provide high quality voice and data communication links for its subscribers. However, there are conditions that can compromise the quality of our service. We have highlighted three common factors regarding the user's environment that can lead to degraded service quality.

1. Obstructions
   For optimal performance, the user's antenna must be able to see the entire sky from 8.2 degrees above the horizon. Nearby tall buildings or similar structures, heavily leafed trees, mountains, etc. can degrade performance if they block the signal between the equipment's antenna and the satellites. A completely open view of the sky is critical in order to maximize reception since the satellite transverse the sky from horizon to horizon during a call connection. A good rule of thumb is that all surrounding obstructions should be lower than the top of a fist which is extended at arms length and the bottom of the fist placed on the horizon (e.g. ~ 8.2 degrees). Note that Iridium performance is immune from natural environments such as clouds, fog, rain, snow, wind and smoke.




2. Cabling
   Installation of an externally mounted antenna is ideal for many applications. It is very important that the cables used for these installations meet the guidelines that Iridium has established for proper performance. For optimal performance, we recommend using the shortest length of cable and the fewest number of connectors possible. Information regarding the proper equipment and installation of external antennas is available on the Iridium Extranet at Library\Products & Services\Product Training\Iridium Antenna Cables.ppt.


3. RF Interference
   All wireless devices are susceptible to RF (radio frequency) from other wireless devices. This problem is especially evident when numerous antennas and broadcasting devices are located within close proximity to each other, for example, on a shipping vessel. It is important that when an Iridium system is installed, that certain considerations be taken into account for best performance.

Causes of RF Interference

Iridium subscribers who operate near INMARSAT terminals have contacted Iridium regarding loss of signal quality. The power with which INMARSAT units transmit often overpowers the Iridium unit's ability to properly maintain a quality connection with the satellite constellation. INMARSAT terminals are often found in the same locations as Iridium subscribers, such as harbors, airports and especially on ships. Other sources of RF interference such as Globalstar units, radar devices and broadcast stations can provide interference for Iridium units, but usually are not encountered as frequently as INMARSAT terminals.

The specific location of the INMARSAT antenna in relation to the Iridium antenna partially determines the degree of signal degradation that an Iridium subscriber can expect to experience. All Iridium units are susceptible to this interference, regardless of the type of antenna being used.

Generally speaking, the Iridium 9505 within 10 m to 52 m of an operational INMARSAT M4 terminal likely will experience degraded performance. The specific position of the INMARSAT terminal in relation to the Iridium handset will determine the amount of degradation that might be expected. Susceptibility to interference applies to 9500 and 9505 equipment (including L-Band Transceiver (LBT) equipment) which are contained in such products as AIRSAT, BlueSkyLink, EuroCom, SatTalk, SkyConnect, etc.

Symptoms of RF Interference

Symptoms of RF interference often resemble those that arise when an Iridium phone is being operated with an obstructed view of the sky. Some of these symptoms include: erratic or no signal strength indicators, dropped calls or warbled voice. Another symptom may include the Iridium logo missing on the LCD (the 9500 will still have a radio tower icon on the blank screen, but the 9505 will not). In the case of RF interference, these symptoms may be intermittent or persistent, depending largely on the interference source, distance, strength and frequency of broadcast.

Mitigation of RF Interference

Degradation of service due to RF interference can be dramatically improved by either increasing the distance from the source of the interference or using an external bandpass filter. A table containing the recommended distances from an INMARSAT unit is listed below. This assumes the INMARSAT antenna is not pointed directly at the Iridium user. For your convenience, the chart includes distance recommendations that include guidelines for both with and without a bandpass filter. For questions or troubleshooting, please contact the Iridium Tier II Support Team at +1.480.752.5100.

Filter Information:

An effective filter is available directly from the manufacture, K&L Microwave. The unit is currently in use by the US Navy. The filter characteristics and contact details as follows:

K&L Microwave
408 Coles Circle
Salisbury, MD 21804

Greg Carmean (gcarmean@klmicrowave.com)
(410) 749-2424 or (410) 219-3981

Part Number: 6FVSP-1622.375/X8.25-NP/N
Passband: 1618.25Mhz-1626.5 Mhz
Center Frequency: 1622.375 Mhz
Insertion Loss: 1.1 dB
40 dB Rejection (1616.25-1628.375)
Physical Size: 7.8" L x 1.8" W x 0.8" H
Cost: 1-5 pieces @ $600 ea
          6-10 pieces @ $450 ea
          11-24 pieces @ $405 ea
          100 pieces @ $310 ea
          500 pieces @ $255 ea

An alternate manufacture is Lorch Microwave.

Lorch Microwave
1725 North Salisbury Blvd
PO Box 2828
Salisbury, MD 21802

Julie Passon
jpasson@lorch.com
(410) 860-5100

Part Number: 6CFX-1621/10-5
Center Frequency: 1621 MHz
Insertion Loss: 1.5 dB
Size: 5" x 3.5" x 1.5"
Weight: 1.65 lbs
Connectors: SMA-Female
Cost: 1 @ $645, 10 @ $465 ea, 100 @ $345 ea, 500 @ $270 ea

Note: All prices are subject to order confirmation with the contacts provided.