New Study Compares Winlink Digital Modes Performance

HF Mode measurements under varying S/N and MPG conditions.

5 July 2020 -- A revision of a study evaluating Winlink digital modes using the new IONOS HF Path Simulator was published today. Hardware SCS modems running PACTOR 2, 3 and 4 were evaluated as were sound card modes WINMOR, ARDOP and VARA across a variety of channel models and across a range of signal to noise conditions for HF. VARA testing included a new VARA 500 500Hz mode. VARA FM and AX.25/FX.25 packet were simulated for a VHF channel.

Spoiler alert: The SCS modems did very well as you would expect. The much less expensive VARA HF did especially well across the range of conditions tested. The SCS modems and VARA could run long test cases without losing a connection while ARDOP and WINMOR were slower and less reliable for lower SNR MP cases. VARA FM crushed AX.25/FX.25 VHF cases.

The complete paper is available in PDF format from the link below.

--The Winlink Team

V4Chat is Deprecated

June 22, 2020 -- The V4Chat Program has been available for download here for several years. The program was created as a testbed for the experimental V4 protocol/mode and served it's purpose well, but it did gain popularity after the testing program among Ham experimenters as a fun program for on-air chats. Because of the Winlink Team's limited resources, our development and use of improved modes, and the decline in the on-air use of V4, we have decided to deprecate both the program and mode. V4Chat support will no longer be available from the Winlink Team. Users who have registered the program within the last six months are eligible for a refund from ARSFI by simply requesting it by email and including your callsign and full name. Users interested in a similar chat program using a modern protocol should look at VARA Chat, available at

--The Winlink Development Team

A New Open Protocol is Coming

A new, open radio protocol is in the future for Winlink users, and for amateurs everywhere. ARDOP (Amateur Radio Digital Open Protocol) is a new cooperative radio protocol project in which the Amateur Radio Safety Foundation and Rick Muething, KN6KB, of the Winlink Development Team is proud to have a major role. ARDOP will ultimately replace WINMOR in the Winlink system because of it's superior features and multiple platform (OS) support.

The protocol design is open, and the software implementations will be open-sourced. This means you can expect the protocol to take different forms, like a virtual TNC using sound-card software on Windows, Linux, Apple OS X, iOS, and Android, or in hardware, like a USB plug-in or 'add-on box' using today's low-cost DSP CPU chips.

What can you expect of this new protocol? Features like bandwidth negotiation, received signal quality feedback in ACK and NAK, auto-timing, more bandwidth options and a wider range of performance. It will be optimizable for both HF and VHF/UHF radio channels (SSB or FM modes), offer VHF/UHF repeater support, and use both ARQ for connected communications and FEC (forward error correction) for broadcasts. It will allow multi-language messages with full binary support for UTF-8 character set. And you can expect advances in speed and efficiency in noisy, multi-path propagating channels, and effective busy-channel detection to minimize the chance of interference with other communications.

Rick said, "Another goal in this effort is to put something out there in several OS and languages that has a chance (maybe just a slight chance!) of getting some other developers interested in learning about and promoting DSP digital modes. It will be easy to add/test additional modes and extend the protocol. For instance, this morning I did the initial integration and testing of a special super robust data mode (16FSK) that should perform very well in very poor multipath and aurora only took a few hours to add the data mode and start testing it. I think if the code is open, yet with compatibility controls to insure conformance so versions are compatible, it just may help some of those not so versed in DSP to learn and eventually contribute."

Since April, Rick has been making satisfying progress wringing out bugs and tuning the protocol with the help of a team of alpha testers, Neil Hughes of the Winlink Development Team conducting endless tests. John Wiseman, G8BPQ, along with Matthew Pitts, N8OHU, have contributed to the specification and open source planning. John has been testing and integrating the virtual TNC into the BPQ client/server. Soon, beta testing will be announced and if interested--and for your promise to assist and make accurate reports--you can get involved in the testing, probably early this Fall.

We've put together an overview page that should answer any questions you might have, and send you to the right places for information. Exciting times! The Radio Art improves!

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