SatSig topic:

pointing to IS904

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Nov 4^th, 2008 at 4:54pm

Dear sirs,
i have been pointing to other satellites but i have never pointed to IS904.when i try pointing to IS904 i can't get the signal.i was pointing to this ISP Bongoo.net with frequency 3933mhz at 60.0°E.when i had this difficulty,i decided to point to IS902 at 62.0°E then i try moving the antennae 2.0°E so that i can get IS904 to no avail.sir,kindly advise are they some technics pointing to IS904?
thanks khan felix

Nov 4^th, 2008 at 5:49pm

The polarisation of your wanted signal on IS902 (62E) may be different from the polarisation of your wanted signal on IS904 (60E).

Find out what your existing polarisation is called and what the new one is called. If (and only if) it needs changing you will need to unbolt the joint between the OMT and the polariser and reattach after turning one part 90 deg.

You don't give your location. If you are near the equator in Africa the elevation will change by about 2.5 deg and there will not be much azimuth change. Elsewhere the repointing may require a diagonal movement. Around the Seychelles and Mauritius do the exact satellite az-el calculations for southern Africa. The change in angle is greater then 2 deg since you are nearer to the satellite than the centre of the earth.

You need to retune your modem to the new carrier on the new satellite.

Best regards. Eric.

Nov 5^th, 2008 at 12:18pm

Thanks very much sir,my location is Buea-cameroon.Sir is IS904 located on the normal axes with other satellites or it is out of axes like W3A?
thanks felix

Nov 5^th, 2008 at 12:36pm

Go here for satellite dish pointing in Cameroon

You say you were tuned to 3933 MHz. This is in C band and Intelsat satellites (and most other C band satellites) use circular polarisation in C band since that is what works well in the tropics, where the actual polarisation angle varies due to the ionosphere. At lower frequencies, like L band for Inmarsat, it even goes right round in circles. There is no polarisation adjustment angle required. You simply have to build the feed assembly the correct way at the OMT/Polariser joint. The linear polarisations of the OMT have to be put at + / - 45 deg either way from the line of polariser pins or slots. One way will give Right hand circular polarisation, the other Left hand circular polarisation. No adjustment angle is required - rotation of circular polarisation has no effect.

W3A is a Eutelsat satellite and its Ku band linear polarisation may be misaligned slightly, but this is not of significance in terms of finding the satellite. Fine adjustment of your Ku band transmit polarisation is always need with measurement co-operation of the VSAT hub.

Find out from your service provider the names of the polarisations and the receive frequencies and symbol rates of your wanted carriers on each satellite IS902 and IS904.

Best regards, Eric.

Dec 7^th, 2008 at 7:19pm

Hi Eric,

the installer in the meantime has found the satellite.

Gretings

Markus
level421
Germany