TV4RV APRIL NEWSLETTER
Vol. 6 - No. 4

SATELLITES - AZIMUTH ELEVATION AND TILT/SKEW

On October 4, 1957 Russia launched the first artificial Earth satellite, named Sputnik 1.  On February 1, 1958 the United States followed by launching Explorer 1.  There are currently more than 1070 operational satellites in orbit around the Earth, about 50% being launched by the U.S.  These satellites provide radio and TV programming, GPS (Global Positioning Satellite) navigation, weather forecasting, military support and many other functions.

When getting satellite signals at home, few of us think about how these signals actually get to our TV set.   We simply turn on the TV with the remote and the picture comes onto the screen.   The installation of the satellite components was usually done by a professional installer, so there is little left for us to be concerned with.

It's when RVers decide to bring their satellite system on the road that they must learn what happens before they press the ON button of the remote to make everything work.   This month's article will explain a little about satellites, and specifically, the terminology used in the industry when setting up the equipment.  With this knowledge, you will have a better understanding of the importance of each factor of the dish setup.   For the purpose of this article we will focus on only one satellite, DirecTV's primary satellite - 101.

First let's understand what the 101 means.  All satellites are in a fixed position in orbit around the earth.  Picture that orbit as a tape measure in the sky, over the Equator, around the Earth, with markings from 0 to 360.  Those numbers represent degrees of longitude.   Greenwich England is at 0 degrees longitude, which is also why the Earth's day begins and ends at Greenwich Mean Time (GMT) upon which all clocks are based.

The longitude of the center of the continental United States is 100 degrees.  By placing their satellite at 101 degrees longitude, DirecTV put the satellite directly in the middle of the country for maximum coverage.  Now how does this relate to azimuth?   As you move to different places in the United States the angle left or right (azimuth) that you must point the dish will change.  Remember, the satellite is in the CENTER of the U.S., over the Equator.  Think "South of Texas".   So, if you are in New York, you will need to point more towards the south west, while if you are in California, it will be more south east.  You will need to refer to a setup guide that gives the exact azimuth according to the postal Zip Code where you are staying.   This guide is often built into the receiver's setup program.  The azimuth setting is based on magnetic north, not true north, so follow your compass settings.

The other measurement used in positioning objects or places on the Earth's surface is called latitude.  Starting at the Equator, the Earth is divided into 90 segments of latitude to each pole, 180 total.   How does this relate to elevation?  Remember, the satellite is in a fixed position above the Equator.  When we are in Texas we are closer to the Equator, so the satellite will seem higher in the sky than when we are in North Dakota.  So we need to adjust the elevation setting on the dish each time we move to another area.  This is usually a small move of a few degrees.  This setting is also included in the setup information.

The third setting, Tilt (Skew with DishNet) involves turning the dish on its axis to align it with the orbit in the sky.  This adjustment is only necessary when you are trying to hit 2 or more satellites.  If you look at the map above, notice that the latitude (horizontal) lines are curved as the go across the country.  As you go closer to the North pole, the curve changes slightly.  Your satellite dish is curved to mimic this curve so when you are adjusting the tilt, you are aligning the dish with the orbit's curve.  The tilt setting is the third and final setting you will need when aligning your satellite dish.  This setting is also part of the setup information in your receiver.

Remember also, it is essential that the dish mast be perfectly plumb for all these settings to correctly align the dish with the satellite.