Hamilton County ACS/ARES®

VARA HF Version Info (m)

Executive Summary

VARA HF 4.9.0 and 4.9.1 Compatibility Concerns

Date: November 12, 2026
Subject: Potential disruption of Winlink HF communications beginning January 1, 2027

Overview

Recent technical investigations have identified a potentially significant compatibility issue between VARA HF versions 4.9.0 and 4.9.1, which could affect Winlink radio communications beginning January 1, 2027.

VARA HF is a software modem widely used by amateur radio operators, emergency communications organizations, and Winlink Radio Message Servers (RMS). The reported change could disrupt communications between otherwise properly functioning stations.

Key Findings

1. A date-dependent protocol change

VARA HF 4.9.1 reportedly contains two different communications protocols:

  • Before January 1, 2027: Uses the existing protocol compatible with VARA HF 4.9.0.

  • Beginning January 1, 2027: Selects a revised protocol that is reportedly incompatible with VARA HF 4.9.0.

2. The protocol is selected when VARA starts

Technical investigators report that VARA HF 4.9.1 checks the computer’s date when the application launches.

The selection apparently does not automatically change at midnight. Consequently, a station started in December 2026 may continue operating using the older protocol into January 2027.

3. Identical software versions may become incompatible

Two stations running VARA HF 4.9.1 could fail to communicate if one started before January 1 and the other started afterward.

Restarting the older session may restore compatibility with updated stations but simultaneously prevent connections from stations still operating version 4.9.0.

4. The issue affects radio interoperability

This is a potential over-the-air protocol incompatibility, not necessarily a problem with Winlink Express, computer configuration, radio equipment, or signal quality.

Potential Operational Impact

For ARES, ACS, healthcare emergency communications programs, and Winlink RMS gateway operators, the reported change presents several concerns:

  • Failure to establish HF Winlink connections despite adequate radio signals.

  • Interruption of message delivery between stations operating different protocol generations.

  • Unpredictable gateway availability during the transition period.

  • Possible disruption of emergency communications if software versions and restart procedures are not coordinated.

Recommended Actions

  1. Inventory software versions at volunteer stations, emergency operations centers, healthcare facilities, and RMS gateways.

  2. Conduct controlled compatibility testing between VARA HF 4.9.0 and 4.9.1 before January 2027.

  3. Coordinate software upgrades with regional RMS gateway operators and participating organizations.

  4. Develop a transition plan that includes restarting VARA HF 4.9.1 after the protocol change and verifying successful message exchanges.

  5. Maintain alternate communications capabilities during the transition, including other available Winlink modes and conventional voice communications.

  6. Request official clarification from the VARA developer and Winlink Development Team regarding the protocol change, transition date, and compatibility requirements.

Status of Verification

The reported January 1, 2027 transition is supported by independent technical investigation, including analysis of program files and date-dependent behavior.

However, the precise implementation and intended transition procedure have not been conclusively confirmed through an official developer statement or independently reproduced testing for this report.

VARA FM 4.4.1 was also recently released, but the available evidence does not establish that it shares the same January 2027 compatibility issue.

Conclusion

VARA HF 4.9.1 presents a credible risk of communications incompatibility beginning January 1, 2027.

The most concerning aspect is that stations running identical software versions may become incompatible depending on when their modem applications were started.

For organizations relying on Winlink for emergency communications, this issue warrants immediate attention, coordinated testing, and transition planning.

Recommended priority: Address this issue before January 1, 2027, to minimize the possibility of disrupted emergency message delivery.

Technical reference: VARA HF Compatibility Investigation — November 2026

Official software repository: https://downloads.winlink.org/VARA%20Products/