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VARA is a family of high-performance software modems for amateur radio, developed by EA5HVK (José Alberto Nieto Ros). VARA has become the de facto standard transport protocol for Winlink and is increasingly used for other data applications. It offers dramatically higher throughput than older amateur radio data protocols, making radio email and file transfer practical where they were previously painfully slow.
VARA comes in two versions: VARA HF for high-frequency (shortwave) bands, and VARA FM for VHF/UHF FM channels.
VARA HF is a sound card-based modem that operates through an HF transceiver's SSB audio path. It uses OFDM (Orthogonal Frequency Division Multiplexing) with multiple subcarriers, adaptive modulation, and forward error correction to achieve high data rates within the constraints of HF radio.
Key characteristics:
The adaptive speed control is one of VARA's most important features. An HF channel can change rapidly — fading, interference, and propagation shifts happen constantly. VARA reacts to these changes in real time, squeezing maximum throughput from whatever conditions are available.
VARA FM is designed for VHF/UHF FM radio channels, where conditions are much more stable than HF. Without the challenges of HF propagation, VARA FM can achieve significantly higher speeds:
VARA FM connects through the radio's audio path, similar to VARA HF, but optimised for the wider, more stable bandwidth of FM.
VARA's primary use in amateur radio is as a transport protocol for Winlink. When you send or receive email over Winlink, the Winlink client software (like Winlink Express or Pat) uses VARA as the modem to transfer data between your station and the RMS gateway.
Before VARA, HF Winlink typically used Winmor (~500 bps maximum) or Pactor (expensive hardware modems). VARA brought Pactor-like performance using only a sound card interface — no specialised hardware needed.
| Protocol | Type | Max speed (HF) | Cost |
|---|---|---|---|
| VARA HF | Software modem | ~8,400 bps | Free (limited) / ~$70 (full) |
| ARDOP | Software modem | ~1,200 bps | Free (open-source) |
| Winmor | Software modem | ~500 bps | Free (discontinued) |
| Pactor IV | Hardware modem | ~5,500 bps | ~$1,500–$2,000+ |
| Packet (AX.25) | TNC | 300 bps (HF), 1,200 bps (VHF) | Free (with software TNC) |
VARA's combination of high speed and low cost (software-only, no special hardware) has made it the most popular choice for Winlink by a wide margin.
VARA HF and VARA FM are separate software applications, available for Windows only (as of the current version). They run as background modem processes that other applications (like Winlink Express) connect to via a local TCP/IP port.
Free version: VARA offers a free version with reduced speed (limited to approximately 175 bps for VARA HF). This is functional for basic email but very slow.
Registered version: The full-speed version requires a paid licence (approximately $70 USD for VARA HF, with VARA FM sometimes included or available separately). The licence is a one-time purchase tied to your callsign.
While VARA itself is Windows-only, Linux users can run it under Wine with good results. The Pat Winlink client on Linux integrates with VARA running under Wine. Some community guides document this setup in detail.
VARA uses the same digital station setup as other HF digital modes:
Audio level settings are critical for VARA performance. The VARA software includes a built-in audio level indicator — follow its recommendations and keep ALC at zero on the radio.
VARA's settings include:
Winlink Express includes automatic VARA integration — when you select a VARA HF or VARA FM channel, it launches and configures VARA automatically.
While Winlink is VARA's primary application, the modem can be used by other software for general-purpose data transfer over radio. Applications that support VARA as a transport include: