There have been a lot of great comments about the LVB Tracker. I will add one that hasn't been made.
I used the LVB Tracker, assembled by WB8CXO, on my Satellite Grid Expedition around Lake Superior in August 2010. It drove a G5400b rotor on a tripod mounted in the bed of my F150. The rotor which supplies power to the LVB tracker through the DIN plug in the rotor control box was powered by an AC inverter. That inverter was powered on/off hundreds of times during the 5000 mile trek, on paved and on dirt/gravel roads. I had calibrated the LVB Tracker before we left and I never had to re-calibrate it during the entire trip. It worked flawlessly under the most demanding conditions.
You don't want to be fiddling with your equipment when you are on an expedition. There is enough going on that demands your attention without having to make adjustments. SatPC32 worked every time and the rotor never missed a beat. A few hundred operators have some pretty rare grids confirmed thanks to these great products (and my XYL W8ZJB for letting me work the birds during our 5 week vacation).
Both SatPC32 and the LVB Tracker are sold by AMSAT. Buying them helps AMSAT and gives the buyer bulletproof software and hardware so you can concentrate on operating. When you purchase them it's a win-win situation.
73, John K8YSE