vertical polarized signals

This could be that the carriers have different levels, or it could be that your LNB has degraded performance on one polarisation.

Try turning the LNB physically by 90 deg.

If the problem remains unchanged then the cause is different carrier levels on each polarisation.

If the problem now appear the other way round then it suggests that one side of the LNB is faulty.  Try turning the LNB physically when you want to watch on the other polarisation, or get a new LNB. Check it is dry inside ! If switching the polarisation involves a magnet or actuator check it works.

Review all the possible channels etc on Intelsat 17 (66 east) and APSTAR 2R (76.5 east) and the beam coverage patterns by going to https://www.lyngsat.com

Best regards, Eric.

I am having to stretch my imagination to think of any explanation for your observation.
- maybe your dish is made of wire mesh and the wires with a particular orientation in the mesh are corroded ?
- maybe your satellite TV receiver is sending out very low DC volts when set to vertical ?  It should be +13 V for vertical and +19 V for horizontal. Is your cable very long or maybe corroded internally due to moisture, causing high resistance ?  If this is the case then you should get good reception using Horizonal selected and if you then turn the feed 90 deg physically then you should get good reception on vertical as well.

As seen from Dhaka, Bangladesh, when you point your dish at the 66 or 76.5 deg east satellites you will need to apply polarisation adjustment amounts of approx +43 or +29 deg clockwise as viewed looking towards the satellite in the sky. The satellites are to the west of South.

For example, to align the LNB for the 76.5E satellite you need to set the LNB initially upright, then turn it +29 deg clockwise as viewed looking forwards towards the satellite in the sky.  Your Horizontal and Vertical polarsations will both be tilted be the same +29 deg amount clockwise.

For exact polarisation adjustment angles see https://www.satsig.net/maps/satellite-dish-pointing-india.htm
wxw
Best regards, Eric.

See: https://www.lyngsat.com/Intelsat-7-10.html

Are you receving 4012 MHz H TARA Muzik ?

If so, there may be a cross pol 'feeds' carrier, also at the same frequency, but perhaps not all of the time.

I note that this is C band operation, with linear polarisation, just about in the tropics.

C band linear is not a good idea in the tropics as it suffers from ionospheric Faraday rotation.  The two polarisations (V and H) stay at right angles to each other and the baseline angles are as calculated, clockwise to the south west. Anticlockwise to the south east.  But, the polarisations are rotated by the ionosphere by varying amounts.  As your feed rotation is fixed, you experience varying levels of cross polarisation interference.

At S band and L band the polarisation may rotate completely. At C band there is problem. At Ku band and Ka band Faraday rotation is not a problem, but the higher do frequencies suffer from bad rain attenuation and rain noise.

Do you adjust your linear polarisation angle when you repoint to different satellites. Use this to get your adjustment angle https://www.satsig.net/maps/satellite-dish-pointing-india.htm but note that the actual optimum angle will be varying according to the sun's output (space weather.)

In the tropics, C band circular polarisation is preferred.

Best regards, Eric

I am sorry. I could solve the problem in last July,2012.

A solid mesh of 6 feet diameter solved the problem but with too much precise alignment. Thanks to all who helped me.....