If you are on OS X, you can skip this step.
com0com is an open-source utility that emulates pairs of virtual serial ports (VSP), connected by a virtual null modem cable. These virtual ports provide a channel for the RHR Helper to communicate with your logging software.
During the installation process, uncheck CNCA0 <-> CNCB0.
On the final step of installation, check Launch Setup.
You will be presented with the com0com setup application. On the left side you will see Virtual Port Pair 0, which is the set of virtual ports that the Helper will use to communicate with your logger. Take note of the COM port numbers of these two ports. In the example below, COM17 and COM18 have been created. Your port numbers may be different – for example, you might see COM2 and COM3.
You will need to refer to the COM port numbers later on, so write them down. This page will refer to them as the LOW and HIGH COM ports, in reference to their COM port number.
We need to set up com0com to always have the DSR, DCD, and CTS pins to be ON for the low COM port (the one on the left). Click and drag from the red ON pin to the green DSR pin. Do the same for ON to DCD, and ON to CTS. Click Apply. Your resulting pinout diagram should look like this: