SOONTAI   Technical Note  
 
  Satellite TV Reception  
 
 
 1.   To receive all kinds of wireless broadcasts, an antenna is necessary.
The type of antenna varies with the kind of broadcast to be received. Satellite broadcasts require a special satellite antenna called "dish" or "satellite dish".
 
 2.   Currently satellite broadcasts use two different frequency bands: C-Band with a frequency range from 3.7 to 4.2GHz and Ku-Band, which is divided in a low band from 10.7GHz to 11.7GHz (Lo: 9.75 GHz) and a high band from 11.7GHz to 12.75GHz (Lo: 10.6GHz).
* Lo = Local Oscillation
 
 3.   The satellite signal is reflected from the dish to the Freed-Horn and from there directed to the LNB (Low Noise Block Down Converter).
 
 4.   The LNB detects the signal relayed from the feed, converts it to an electrical current, amplifies it and lowers its frequency. The output level of a typical LNB is around 55-65dBuV.
 
 5.   The European satellite TV system:
Low band: 10.7GHz - 11.7GHz (Lo: 9.75GHz)
High band: 11.7GHz - 12.75GHz (Lo: 10.6GHz)
Therefore the frequency range from the LNB for the Low band is:
950MHz-1950MHz (10.7GHz minus 9.75GHz) to (11.7GHz minus 9.75GHz)
and for the High band:
1100MHz-2150MHz (11.7GHz minus 10.6GHz) to (12.75GHz minus 10.6GHz)
 
 6.   To avoid interference between odd and even numbered channels, adjacent frequencies are polarized in opposite directions. Satellites usually broadcast signals with either vertical, horizontal, left hand circular (counter-clockwise rotation) and right hand circular (clockwise rotation) polarization.
 
 7.   The receiver uses different voltages to signal the LNB to select between
vertical (V) and horizontal (H) satellite signals.
 
 8.   The voltage used by the receiver to signal the LNB to choose between vertical and horizontal signals is 12-14V for vertical and 15-18V for horizontal mode. Therefore multi-switches usually operate at a voltage range of 14.6V+/-0.3V.
 
 9.   Currently LNBs can be divided into "Universal" LNB, "Twin LNB" (Universal Twin LNB) and "Quattro LNB".
 

What is a "Universal LNB" ?
 
LNB's Lable :
One Outlet
Note:
Only one F-type outlet
Lo band (10.7-11.7GHz)
Hi band (11.7GHz-12.75GHz)
Can receive two bands, analog Lo band and digital Hi band.
LO (9.75GHz + 10.6GHz) Two oscillation frequencies for Lo and Hi band.
1x H+V 1 (one F-type outlet), H (horizontal), V (vertical).

This type of LNB has one F-type outlet and can receive "Lo band H+V" and "Hi band H+V". It is often used for normal family type setups.
 
What is a "Twin LNB" (Universal Twin LNB) ?
 
An "Universal Twin LNB" is two "Universal LNBs" in a twin box (for both Hi and Lo band). A "Twin LNB" or "Analog Twin LNB" is two analog LNBs in a twin box (only analog Lo band). See also ASTRA webpage.
 
What is a "Quattro LNB" ?
 
This type of LNB is used in SMATV systems. It has four F-type connectors: "Lo band V", "Lo band H", "Hi band V", "Hi band H" and is often used with a 5xn or 9xn multiswitch.
* "Quattro LNB" is also called "Quattro-band LNB" or "Quad LNB", see also ASTRA webpage.
 
10.   3x4 or 2x4 multiswitches are used with Twin LNBs. When more than two receivers share one satellite dish multiswitches are also necessary.
 
 
   

Published: Aug 30, 2000
http://www.soontai.com

 
 
 
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