After testing the Minnesota DOT RTK network last year, Dave Lagerstedt of GPS Services in Adams, MN, now works with 15 ag customers. “Our customers are very pleased with it,” he says. “If we have any issues at all, it is with the cell phone providers.”

Even cell phone problems have been relatively minor. In most instances, customers have required only external antennas to get a reliable cell signal, even in bluff terrain.

“We use an external antenna most of the time,” Lagerstedt says. “In some areas, we also use a booster [amplifier]” to improve the signal. Data transmission often continues even where voice calls tend to drop. (For more information about improving cellular communications signals with antennas and amplifiers, see “Wireless farm,” August 2008, page 31.)

Customers access corrections with a “smart” cell phone (the HTC 6800 is the company's preferred model). The cell phone relays signals to GPS controllers via Bluetooth wireless and software from InTime ( for a package price of $4,400, excluding the phone.