how to calculate satellite dish signal loss due to compromised pointing

popolon

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My Satellite Setup
Teleste 5m,invacom quad (28.2E), invacom quattro (26.0E). Triax multiswitch (1in, 8 out)
-TT 1600 PCI. Prof 3701 PCI.
-DR HD F15
-Ariva ferguson A120
Aerial 3m dish (7W-28.5E) + motor+ invacom quad.
-Ariva ferguson A220.
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Hi!

Now that Astra 2E/2F are so apart from each other, how can you calculate affected loss of signal from ideal pointing, when using 5M dish ? I mean if dish has 0.35 degree beam width, what would be signal loss when pointing error would be for example 0.1 degrees? What is the calculation formula for this loss?
 

hvdh

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Interesting question!
See the formula for Gr on page 5 here: https://www.satprof.com/resources/pdf/Brooker_Antenna_Pointing_Accuracy.PDF

For example your antenna has 0.35º full beamwidth, so the -3 dB points are 0.175º off-axis (half beamwidth).

Assuming you point at 28.20º E, then the loss for 28.35º E is:
Gr = 3 * (0.15/0.175)^2 = 2.2 dB

Assuming you point at 28.275º E (inbetween), then the loss for both 28.2º and 28.35º E is:
Gr = 3 * (0.075/0.175)^2 = 0.55 dB
 

popolon

Member
Joined
Jun 3, 2009
Messages
77
Reaction score
76
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Location
south west of Finland
My Satellite Setup
Teleste 5m,invacom quad (28.2E), invacom quattro (26.0E). Triax multiswitch (1in, 8 out)
-TT 1600 PCI. Prof 3701 PCI.
-DR HD F15
-Ariva ferguson A120
Aerial 3m dish (7W-28.5E) + motor+ invacom quad.
-Ariva ferguson A220.
My Location
Finland
How is signal loss for multi LNB setup calculated, for example if first LNB is at the focal point, and then the other LNB is for secondary satellite signal? So what is signal loss for that second LNB?
 
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