VARA is a family of sound card modems for moving data by radio. It was written by José Alberto Nieto Ros, a ham in Spain, and comes in versions for HF (VARA HF), for FM radios on VHF and UHF (VARA FM), and for the QO-100 geostationary satellite (VARA SAT).
Many hams meet VARA through Winlink, the radio email system, where VARA HF and VARA FM carry mail to and from gateway stations. It also carries live keyboard chat: VarAC, a program that is free for licensed hams, uses the VARA protocol for real-time conversations between two stations.
VARA is a connected mode. The two stations trade blocks of data and acknowledgments, and the modem speeds up or slows down as the band changes. On a good HF path it moves several thousand bits per second inside an ordinary SSB channel, and on a weak path it drops to slower, tougher levels. There is also a 500 Hz narrow mode for crowded bands.
On the air it sounds like a burst of rushing noise, a pause, then a short reply from the other end. On a waterfall you see a solid block of signal rather than a thin trace.
VARA is not open source. You can download it at no cost from links on the author’s site, but he sells a license, and an unlicensed copy does not run at full speed. His guide notes that gateway stations get full speed without a license. Check the author’s site for the current terms before you buy.
VARA keeps your transmitter busy, so set the drive level the way the documentation describes and keep ALC action low. Listen before you connect, too. A gateway cannot always hear a conversation that is already on the frequency.
At a Glance
- Category
- Digital data
- Bandwidth
- A 500 Hz narrow mode, plus wider modes that fit within an SSB channel
- Speed
- Adapts to conditions, up to several thousand bits per second on HF
- What you need
- A sound card interface and a Windows computer (some hams run it under Wine on Linux)
- Where to listen
- Winlink gateways and VarAC users rather than one calling frequency