NTNUJAVA Virtual Physics Laboratory
Enjoy the fun of physics with simulations!
Backup site http://enjoy.phy.ntnu.edu.tw/ntnujava/
November 19, 2017, 10:16:20 am *
Welcome, Guest. Please login or register.
Did you miss your activation email?

Login with username, password and session length
 
   Home   Help Search Login Register  
You cannot always have happiness but you can always give happiness. ..."Mother Teresa(1910-1997, Roman Catholic Missionary, 1979 Nobel Peace Prize)"
Google Bookmarks Yahoo My Web MSN Live Netscape Del.icio.us FURL Stumble Upon Delirious Ask FaceBook

Pages: [1]   Go Down
  Print  
Author Topic: Satcom Cross-polarization of V / H  (Read 9813 times)
0 Members and 1 Guest are viewing this topic. Click to toggle author information(expand message area).
audioviking
Newbie
*
Offline Offline

Posts: 1

«
Embed this message
on: October 28, 2009, 06:13:41 am » posted from:Plano,Texas,United States

I am a technical instructor for satellite technologies. One of the key concepts is also the hardest to explain.

-aiming a satellite dish to something you cannot see.
-fine-tuning that alignment.
-adjusting the skew of the LNA/B to align with correct polarization of intended signal
-show what happens if you look at opposite polarity.

Anyone here know of such a simulation?

regards
Travis
Logged
Fu-Kwun Hwang
Administrator
Hero Member
*****
Offline Offline

Posts: 3080



WWW
«
Embed this message
Reply #1 on: October 28, 2009, 03:55:25 pm » posted from:Taipei,T'ai-pei,Taiwan

Are you talking about something related to the following?

Quote
from http://en.wikipedia.org/wiki/Satellite_dish
The parabolic shape of a dish reflects the signal to the dish’s focal point. Mounted on brackets at the dish's focal point is a device called a feedhorn. This feedhorn is essentially the front-end of a waveguide that gathers the signals at or near the focal point and 'conducts' them to a low-noise block downconverter or LNB. The LNB converts the signals from electromagnetic or radio waves to electrical signals and shifts the signals from the downlinked C-band and/or Ku-band to the L-band range. Direct broadcast satellite dishes use an LNBF, which integrates the feedhorn with the LNB. (A new form of omnidirectional satellite antenna, which does not use a directed parabolic dish and can be used on a mobile platform such as a vehicle was announced by the University of Waterloo in 2004.[1]

The theoretical gain (directive gain) of a dish increases as the frequency increases. The actual gain depends on many factors including surface finish, accuracy of shape, feedhorn matching. A typical value for a consumer type 60 cm satellite dish at 11.75 GHz is 37.50 dB.

With lower frequencies, C-band for example, dish designers have a wider choice of materials. The large size of dish required for lower frequencies led to the dishes being constructed from metal mesh on a metal framework. At higher frequencies, mesh type designs are rarer though some designs have used a solid dish with perforations.

A common misconception is that the LNBF (low-noise block/feedhorn), the device at the front of the dish, receives the signal directly from the atmosphere. For instance, one BBC News countdown shows a "red data stream" being received by the LNBF directly instead of being beamed to the dish, which because of its parabolic shape will collect the signal into a smaller area and deliver it to the LNBF.[2]

Modern dishes intended for home television use are generally 43 cm (18 in) to 80 cm (31 in) in diameter, and are fixed in one position, for Ku-band reception from one orbital position. Prior to the existence of direct broadcast satellite services, home users would generally have a motorised C-band dish of up to 3 metres in diameter for reception of channels from different satellites. Overly small dishes can still cause problems, however, including rain fade and interference from adjacent satellites.

 I do not have a satellite dish. I need more information to be able to create a simulation.
Logged
Pages: [1]   Go Up
  Print  
You cannot always have happiness but you can always give happiness. ..."Mother Teresa(1910-1997, Roman Catholic Missionary, 1979 Nobel Peace Prize)"
 
Jump to:  


Related Topics
Subject Started by Replies Views Last post
electrical polarization
Wave
amitavadeb 0 14165 Last post July 14, 2005, 02:13:09 am
by amitavadeb
C=AXB cross product vector relations
misc
Fu-Kwun Hwang 0 20036 Last post February 23, 2007, 08:45:08 pm
by Fu-Kwun Hwang
C=AXB cross product vector relations
misc
ahmedelshfie 0 6085 Last post May 21, 2010, 02:02:32 am
by ahmedelshfie
projection of a vector: inner product A‧B, and cross productor AXB
misc
Fu-Kwun Hwang 0 7455 Last post November 26, 2010, 01:23:48 pm
by Fu-Kwun Hwang
Cross a river with a boat
Kinematics
Fu-Kwun Hwang 4 26361 Last post July 12, 2016, 12:16:16 am
by rockmanx4
Powered by MySQL Powered by PHP Powered by SMF 1.1.13 | SMF © 2006-2011, Simple Machines LLC Valid XHTML 1.0! Valid CSS!
Page created in 0.046 seconds with 22 queries.since 2011/06/15