DISH 500 RECEPTIONThis webpage will describe how to receive "DISH 500" using the manual roof-top mounted satellite dish.  It is also applicable to some automatic satellite dish systems.
When we first purchased our DISH system in early 1998, all the programming was provided from one satellite.  This was fine, until 1999, when DISH introduced their DISH 500 system which receives programming from two satellites - commonly referred to as the 119 and 110 satellites..  I got along fine with my America's Top 100 programming from DISH, as this only required accessing one satellite.  However, in 2001, the FIA World Championship and Tour de France moved to two networks that were only available on the new, second satellite.  These networks are part of DISH's America's Top 150 package, and almost all of the 50 additional channels are on the second satellite.
To receive signals from two satellites simultaneously from one satellite dish requires a special 20" elliptical satellite dish with dual LNB's.  (DISH refers to this as a "DISH 500" system).  The satellite dish must be adjusted for azimuth, elevation and skew angle to simultaneously.  A special "switch" is also provided to allow the receiver to select programming from either satellite.
Presently, there is no RV satellite dish on the market that allows for a skew angle adjustment.  Although one could utilize an externally-mounted DISH 500 satellite dish, this often is not desirable, especially when boondocking, so I did not want to lose the functionality of my factory-installed Winegard satellite dish.
Here is what you need to do to use your 18" satellite dish as a "DISH 500" system:
Let's assume that you are watching the 119 satellite and you want to change to the 110 satellite.
As a sidenote:
When I upgraded to America's Top 150 programming, I was asked if I had a DISH 500 system.  I recommend that you just tell them "yes".  I told them that I did not have a DISH 500 system and they said that I would need a DISH 500 antenna (satellite dish) AND a new receiver! All DISH receivers are functionally equal, and if you follow the procedure above, you do not need a new DISH 500 satellite dish either.
Thanks to Zane for helping on this!