I've had the same problem. For my setup in the airplane I have two USB/serial adapters for two GPS inputs. I've used the adapters Garmin sells for years because they're cheap (um...cheap if you don't buy Garmin's branded-version of them) - the look like
this [
pccables.com]. Unfortunately they don't work with any 64-bit operating systems so I had to switch.
Turns out there are two other manufacturers that are tons better. One is made by Prolific. They usually look like a cable with blue or purple transparent connectors on the ends (available
here [
pccables.com]).
The other brand is made by FTDI. They're the best but I haven't found a source of pre-made FTDI cables (I put my own connectors on them).
I've tried a couple over the years from Best Buy and Office Depot but they've never been very good quality. Maybe that's changed... but for now I order the Prolific ones when I can.
