Sure, and I'll try to answer a couple of your other posts on the same/similar subjects that you've posted today. First, in regards to saving NMEA strings, there are functions on the File I/O palette that can be used. Write Characters to File should work just fine. Once you have a file saved, you can them simulate the reception of data. If your GPS would noramlly be connected to Com1, connect it to another com port with a null modem cable (tx and rx swapped). Then, in a separate VI, read the saved file and then transmit it out line by line over Com2.