16/07/2020
THINGS TO KEEP IN MIND BEFORE YOU ATTEMPT TO COMBINE
1. The satellites beam must cover your location.
2. Is the satellites located in the same cardinal
hemisphere (East or West)
3. Is the orbital angle between the satellites is
less than 20 degree?
The orbital angles are usually written together
with the name of the satellite e.g. Astra 2F 28.2
deg east.
name> Astra 2f
orbital angle> 28.2e
with this in mind it is easy to calculate the
difference between two satellites.
Example: The difference between ASTRA 2F
28.2e and AMOS 517e is 28.2-17=11.2
this is less than 20deg so it means one can track
the two together on a single dish.
4. The next question is how will i know the distance
between the two lnbs when fixed together.
The difference between the orbital angles is not
the same as the distance between the lnbs.
some of the satellites you can track together
with a single lnb.
example Eutelsat 7 and Ses 5
Amos5 and eutelsat 16
Astra 2f and Badr5
intelsat 20 and Eutelsat 70B.
others you will need another lnb.
the size of the dish will also determine the
distance between the lnbs.
Now let us do a little maths, to make things
easy, We have calculate pre define constant for
three dish sizes. That was gotten from their focal
length ( Check image for more info)
*For 60cm dish (focal length 36cm) = 0.68077cm.
*For 90cm dish (focal length 54cm) = 0.9426cm
*For 1m dish (focal length 74cm) = 1.30917cm
*For 1.2m dish(focal length 76cm) = 1.32699cm
(all the dishes above are with reference to
strong dishes. Your dish focal length may be
different but the difference may not be that
great. We also used Legon's equation for the focal
length of offset dish antenna. You can google it up for more clearification),
with the values we have given above, if you want
to find the distance between two lnbs, just
multiple the value of the correspnding dish by
the difference between the orbtical angle of the
satellites.
