cs601 GDB Feb 11,16
Satellite Communication Dated: Feb 11, 16
Dear Student,
Graded Discussion Board (GDB) of CS601 will open on Monday February 15, 2016 and close on Tuesday February 16, 2016. GDB will remain open for two days, you are required to post your comments within due date.
Discussion Topic
Satellite Communication
Suppose a MATV/SMATV (Satellite Master Antenna Television) company starts operation in the remote city of a country. They have to select satellite communication band for their satellite system. As their major business requirement is minimal interference from a severe weather condition of the city and to provide reliable, consistent service to their customers.
You are required to
a) Suggest a suitable satellite communication band, give a solid reason.
The answer should not be more than five lines.
b) Give names of frequencies polarities for LNB as per selected satellite communication band.
A concise, coherent and to the point comment is preferred over lengthy comment having irrelevant details. Your comment must not be more than 5 lines. Comments, posted on regular Lesson's MDB or sent through email will NOT be considered in any case. Any request about such an acceptance will not be catered.
Best of Luck!
SOLUTION:
Digital signals are transmitted from the satellites on either Vertical (V) or Horizontal (H) polarity for linear feeds, or on Right (R) and Left (L) polarity for circular feeds. Standard big dishes are most likely to have feed horn that can receive linear (H/V) polarity. Other system such as Dish Network and Direct TV use circular polarity.
If you have a big dish, most manufacturer of feed horns such as Chaparral and ADL provide what is called a "Teflon Slab" that can be added to the feed horn which would allow it to receive both linear and circular polarity signals. This will cause a loss of about 1 dB in signal level on the linear polarity signals. A Wideband Chaparral feed horn can receive both linear and circular (Ku band) polarity signals.
In order to receive the digital TV signal, you must have the feed horn set to the correct polarity. For LNBFs, the polarity is controlled automatically by a voltage transmitted form the receiver to the LNBF via the coax cable. The receiver will send the LNBF 18 volts for horizontal polarity, and 13 volts for vertical polarity. For standard LNBs, the polarity is controlled by a motorized motor. In this case, odd channels represent one polarity, and even channels represent the other polarity. Standard satellites have the even channels set the polarizer to horizontal polarity, and the odd channels set it to vertical polarity. If the Satellite Polarity is inverse, then the even channel set it to the vertical polarity, and the odd channels set it to the horizontal polarity. Furthermore, some LNBFs such as Dishnetwork's DP LNBFs control the polarity change by shifting the frequency rather than using 13/18 volts. In fact the new shifted horizontal polarity is 25600 minus the original horizontal polarity.
Dear Student,
If you have a big dish, most manufacturer of feed horns such as Chaparral and ADL provide what is called a "Teflon Slab" that can be added to the feed horn which would allow it to receive both linear and circular polarity signals. This will cause a loss of about 1 dB in signal level on the linear polarity signals. A Wideband Chaparral feed horn can receive both linear and circular (Ku band) polarity signals.