Telenet

Autotrack VSAT

admin — Thu, 24 Jul 2008 01:16:44 +0000

The antenna will be used onboard a ship and it will have to be able to provide uninterrupted satellite usage while under a variety of motion.

What are the key points :

Pointing/Targeting - Accurately driving the antenna to a precise Azimuth and Elevation angles in three dimensional free space to be consistent with where the satellite signal is emanating from.

Stabilization - Maintaining the Azimuth and Elevation pointing angles while the ship is rolling, pitching and turning.

Tracking - Use of the received satellite signal level to continuously evaluate and optimize the pointing angles of the antenna for maximum signal level reception.

Definitions of other relevant terms :

Relative (REL)
Mechanical azimuth rotational position of the antenna relative to the Bow of the ship. When the antenna is pointed inline with the Bow of the ship the REL display should be 360.0/000.0. Range of display is 000.0-359.9.

Azimuth (AZ)
True Azimuth (requires Ships’ Gyro Compass input). the Azimuth pointing angle of the antenna relative to True North (North Pole of the Earth). When the antenna is pointed True North display will be 000.0, East at 090.0, South at 180.0 and West at 270.0. Range of display is 000.0-359.9, Up direction is CW rotation of the antenna.

Elevation (EL)
Elevation pointing angle of the antenna between Horizon (000.0) and Zenith (090.0).

Level (LV)
Pedestal Fore/Aft upright position relative to the Horizon. Level Sensor is a gravity reference to bring the Level Cage (fore/aft) aspect to “level”. This input is used to stabilize Elevation.

Cross-Level CL)
Pedestal Left/Right tilt position relative to the Horizon. Level Sensor is a gravity reference to bring the Level Cage (Left/Right) aspect to “level”. This input is used to stabilize The Left/Right Tilt of the antenna.

Roll
Tilting motion of the ship from side (Port) to side (Starboard).

Pitch
Tilting motion of the ship from Bow to Aft.

Yaw
Serpentine oscillation of the ship along a desired heading (steering badly)

Center of Gravity (C/G)
Center of gravity of the mass of the antenna. Azimuth, Elevation and Cross Level are aligned at the factory to be coincident within 0.003 inch.

Static Balance
Proper 3 dimensional balance of the antenna is critical to stabilization. When properly balanced the un-energized antenna can be pointed to any AZ/EL pointing position and it will remain pointed there when released.

Tangential Acceleration
G-Force exerted on the mass of the antenna as it swings through free space during ship motions.

Link Budget

admin — Thu, 26 Jun 2008 01:38:51 +0000

- The process of correctly sizing uplink and downlink paths.
- Takes into account:

Established Satellite performance

Path Loss (22,300 miles traversing space)

Atmospheric effects (weather, ion storms, sunspots, etc.)

Frequency bands used (Ku, C, Ka)

Hub uplink antenna and amplifier performance

Downlink antenna size and receiver noise figure

Link Budget Rain :

Design for the specified availability

99.5% availability will give you about two days of outage per year

99.9% will give just 8 hours of outage per year

Note that only the Uplink at the Hub can compensate for rain, by using the UPC

Modulation

admin — Thu, 26 Jun 2008 01:33:39 +0000

Inbound Vs Outbound Transmission Characteristics :

Outbound

Continuous output, bandwidth shared among remote sites receiving TDM frames
Emphasis on inexpensive receiver/LNB
High bit rate (up to 32Mbps)

Inbound

Random access, transmitter bursts as required to communicate with the hub
Emphasis on inexpensive modulator
Medium bit rate (up to 2Mbps, with large scale VSAT)

There are many useful source of VSAT information at VSAT Asia and VSAT Name.

Adding Desktop RAM

admin — Tue, 24 Jun 2008 22:25:53 +0000

Nowadays PC becomes home appliance like other electronic devices in a house. Most of family member from child to housewives needs computer to help their works faster finished or just getting an entertainment from PC. But the PC models and technology is growth as fast as mobile devices, and the newest software also usually needs a high requirement of PC hardwires.
For anyone whose want to raise the higher performance, upgrading PC is the best recommendation. Some ways to get higher PC performance is replacing the processor, adding RAM, or replacing other devices such as cards or drives. Caused of computer branded only exactly match with right device to replace, upgrading a branded PC is more difficult than upgrading another electronic stuff. So, if you have a plan to Adding Computer RAM, branded computer such as Compaq, IBM, and Dell are using specific RAM in their CPU. Then, replacing each other RAM is impossible thing to do. It is also impossible to Add IMAC Memory, because this machine is completely different than other general PC.
Memory Deal, as a Hi Tech Company, which concerns on upgrading memory technology, provides solutions for all those problems above. This company provides various products specialized for branded PC memory such as DDR PC2700 Memory that guaranteed match on our PC. So, the compatibility of their products is guaranteed and you have no worries to upgrading our PC for getting the higher performance.

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