No - You can use another rcvr, see below from JD:

It is possible to utilize a different brand of GPS receiver with Yield Mapping, Harvest Doc, Field Doc Basic, Field Doc Air Cart, Field Doc Planter, Field Doc Sprayer, and Parallel Tracking. These Products can utilize the RS232 signal from many brand X receivers.

It is critical that the following messages from the NMEA 0183 standard are in the signal: GGA, GSA, and RMC setup at 4800 baud, Data Bits 8, Parity none, Stop 1, Flow Control none.

Without these messages, the receiver will not function with above listed AMS Products.

It is also important that brand X receiver is installed correctly. For installation of brand X receiver, the brand X receiver will not will not plug directly into the StarFire harness - new wires will need to be added to the processor connector.

Directions for connecting to a Mobile Processor:

At the mobile processor connector (x551), there are no wires available for hooking up to a brand X receiver. From the receiver manufactures wiring diagram, determine which wires from the receiver are the signal transmit and signal ground. Locate pin F on the mobile processor. Pin F is RS232 RX. Add wires of your own to connect receiver TX to pin F. Signal ground should be hooked up through pin C.