We have a slingshot as a modem to get MDOT CORS RTK correction into my Phoenix 300, exporting data through the RS232 cable for steering and variable rate planting. Was working fine several days ago. Now when I turn it on the 300 initializes for a couple minutes then say "No Position" for 30 seconds or so and blinks out and returns back to initializing. Have tried it on RTK, WAAS and GLONASS. It just cycles on and on. Is it the 300 or what? Does Ag Express work on these?