USB-to-Serial Adapters
Most TNCs expect an RS-232 connection to a computer, but computers rarely have RS-232 anymore. They tend to have USB ports instead, so USB-to-serial adapters are needed. There are many USB-to-serial adapters available, but not all of them work well enough for ARES/RACES packet operations. When choosing an adapter, consider these attributes.
- Chipset
The chipset used in the adapter is critical. The FTDI chipset is preferred. The chipset needs:
- Good compatibility with Windows. The FTDI and KeySpan chipsets are excellent at this. The Prolific chipset gives varied results and is not recommended.
- Consistent Windows COM port, so that the adapter maintains the same COM port number regardless of which USB port it’s plugged into. The FTDI and KeySpan chipsets have this; Prolific does not.
- Consistent Linux device name (if running a Linux packet station). This requires the chipset to provide a unique ID. FTDI does this; KeySpan and Prolific do not.
- LEDs
- Some adapters have LEDs which can be very useful when troubleshooting. The most helpful configuration uses multiple LEDs: one for connection, one for transmit, one for receive.
- Cable Length
- A cable is also an antenna, and can bring RF interference into your PC or serial device. Select as short a cable as feasible. Coil up any extra to reduce the antenna effect. The coil will also act as a choke for any common-mode noise on the shield.
- Ferrite Bead
- A ferrite bead on one or both ends of the cable also combats RF interference. tool for combatting RF interference. If you have RF problems, and especially if you operate with the antenna nearby, a ferrite bead is really important. Clip-on ferrite beads can be added to cables that lack them.
- Serial Connector
- Make sure your adapter has the connector that mates with the device you plan to use it with. Most commonly, this will be a male DB-9 or DB-25 connector.
- Head Shape
- Prefer an adapter with some flat space on the connector, so that you can label it.
The following tools can be helpful in dealing with a variety of USB device issues:
- USBDeview by NirSoft
- Show Hidden Devices in Windows Device Manager by Microsoft Support
* Manufacturer, product, and vendor names and images on this page are given as examples and are not endorsed by SCCo ARES/RACES.