C Band Lnb Skew

When one looks at one end of a standard c band lnb,one would observe that it is calibrated in degrees. The calibrations 30-0-30 are the SKEW (or POLARITY) MARKINGS.  For zero degree skew (skew=0),the 0 mark on the lnb should be horizontal. Similarly,for skew=90 degrees,the 0 mark should be straight up or down. Inside the throat of the c band lnb are two probes (antenna). The one parallel to the bar that runs across the diameter of the lnb is the horizontal probe,while the other is the vertical probe. Reception from a given satellite is achieved the three parameters,namely azimuth (az), elevation (el) and lnb skew (or polarity) for the satellite are properly set. These parameters are function of location (longitude and latitude of the installation site) and can be obtained using satellite calculator Correct adjustment of the skew will put the probes (antenna) inside the lnb in the correct position to receive from that satellite. The antenna in the c band lnb are exactly 90 degrees apart and therefore you do not need to worry about choosing between the horizontal or vertical adjustment. That is to say,if you align the vertical adjustment,for example,the horizontal adjustment is automatically correct and vice versa.

For  FIXED DISH SETUP all you need to do is to set your dish to the az and el for the satellite and then skew the lnb. Step 1-Set the c band lnb skew at zero. Step 2-Use sat calculator to obtain calculation for polarity adjustment for the satellite you wish to receive. Step 3-Turn the lnb the appropriate amount of degree from the zero setting and you are good to go. The initial adjustment of the polarity is  done by educational guess. On reception the lnb is turned by small amounts to peak the signal. I  assume the FD ratio of your dish has been properly set.

For a MOTORIZED DISH SETUP you do not need to skew the c band lnb. However, you have to observe the following procedures. Step 1-Rotate your dish to face the horizon. At the horizon el=0 degree. Now turn your c band lnb until the 0 mark points straight up or down. Observe that if this is done properly, the vertical probe inside the lnb should be parallel to your mount pole. This is why it is always emphasized you make sure the mount pole is plump. Setting your lnb this way ensures you get the same polarization (H or V as the case may be) for any transponder as listed by Christian Lyngsat. Step 2- Attach the motor drive. Have the motor drive in position so that the dish antenna is centered on the mount. Now adjust the nuts on the elevation bolt to set the mount for your site latitude,which should be roughly your latitude number in degrees plus about 0.5 degree. Step 3- Adjust the nuts on the declination bolt to obtain the correct setting for your site latitude. The above rough settings should be close enough to acquire a signal on the satellite whose position is closest to your longitude. Also notice that the lnb is automatically and correctly adjusted (skewed) as the motor drive moves the dish from one horizon to the other.