Satellite Dishes

T24

Different kinds of Satellite Dishes



1) Offset antenna

2) Prime focus antenna

3) Flat antenna

4) Cassegrin antenna

5) Multi focus antenna



Offset antennas

These antennas represent just a part of a parabolic or prime focus antenna. Their focus is not in the geometrical centre of the dish but a bit lower. Since the LNB doesn’t stand in the way of the signal these antennas can be smaller than others.



Prime focus antenna

Prime focus antennas have a parabolic shape and characteristic is that the focus is in front of the centre of the parabola in the geometrical centre that is. That means if the LNB is attached to this antenna it can be found above the middle of the antenna and so the LNB blocks a part of the emitted signals and therefore these antennas have to be bigger than offset antennas. Offset antennas replaced these antennas nearly completely. Today they are mostly used for the reception of signals in the C belt, since these are the only antennas that are built in scopes up to 10m.



Cassegrin antennas

These antenna with two reflectors receive signals better. It looks like an offset antenna with the exception that in the place where the offset antenna has a LNB attached the cassegrin antenna has an additional reflector, which has the task to reflect signals coming from the main reflector onto the LNB, which is placed on the LNB-carrier in front of the small reflector. This means the signals are reflected twice before they get to the LNB.



Gregorian dish

A subversion of satellite antenna that uses a concave hyperbolic
reflector that points signals to the converter and that is placed
opposite of the main reflector.



Flat antennas

This antenna is made of many units, which receive signals, afterwards this received signals are united and directed to the LNB. Technically speaking this antenna collects electromagnetic waves. Since this antenna receives through several units it receives a stronger signal. This antenna can be smaller than advised for several areas.



Multi focus antennas

These antennas are made not long ago. They are offset antennas, which have a specially built reflector, which reflects received signals from surrounding satellites to one focus. You can recognize such an antenna easily, since it quadratic and it’s longer than wider.
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T24

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EIRP & DISH SIZE


LNB 0.6dB

EIRP in dB~~~~Dish size in cm.

64----------------22

63----------------24

62----------------26

61----------------28

60----------------30

59----------------32

58----------------34

57----------------36

56----------------38

55----------------40

54----------------45

53----------------50

52----------------50

51----------------55

50----------------60

49----------------60

48----------------70

47----------------75

46----------------80

45----------------90

44----------------90

43----------------100

42----------------110

41----------------120

40----------------120

39----------------135

38----------------150

37----------------180

36----------------240

35----------------300

34--------------- 360

32----------------450

30----------------570

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