Q15X25 is a 15 tone packet mode with a Kiss/AX25 interface, and from its performance, should long ago have replaced conventional packet for HF use! Q15X25 is now available for Motorola EVM, LINUX PC and Windows PC sound card operation.

Q15X25 Described

In the true spirit of Amateur Radio, Q15X25, like MT63 and many other Amateur designed communications modes, is an open protocol (full details are disclosed) and uses open transmissions (can be read by anyone with similar equipment). Anyone can design or adapt the open sourced software to develop their own Q15X25 system. This is markedly in contrast to some commercial HF packet-transfer systems.

Q15X25 is a DSP intensive mode that operates the like a TNC and modem, to provide an ARQ mode designed for AX.25 and TCP/IP on HF with speed and reliability much greater than traditional HF ARQ modems (such as 300 baud packet). It uses 15 QPSK modulated carriers separated by 125 Hertz, each modulated at 83.333 baud. Q15X25 uses FEC (Forward Error Correction), and like MT63, uses time and the frequency interleaving in order to avoid most error sources. The raw transmission data rate is typically 2500 bps.

Motorola EVM

The well known EVM is a specialized DSP unit with a 56002 processor and an excellent codec device for high performance analog processing.

The source of the EVM software is on the TAPR site.

Linux PC

Q15X25 was developed by Pawel Jalocha SP9VRC, at about the same time that MT63 was developed (late 1990's). For many years the only version of Q15X25 available was NEWQPSK for LINUX and sound card, by Pawel. This has been updated and improved by Tomi Manninen OH2BNS. The latest version can be found at here.


There are actually TWO versions of Q15X25 for Windows, and both are still in development. The first is a "nuts and bolts" version ported from the LINUX version and known as the Q15X25 Soundmodem. The software can be found here.

Hot news - MIXW Version 2.07 will include Q15X25, in a well organized implementation which allows single station connects, very easy setup, excellent performance, and much easier tuning than other versions (it has a good waterfall display). At present there are no higher layers, but dedicated applications are being considered (bulletin boards, gateways, message handling systems?) as separate products. Numerous stations are currently testing the MIXW version. It has not yet been released. Keep an eye on the MIXW Web Site for an announcement.

Q15X25 Operation

Most operation is on or adjacent to the MT63 calling frequency, 14.1095 MHz USB. After all, the users tend to be the same people! 3635 and 3560 kHz LSB are also used in the South Pacific. Who are the current users? Here's a short but not exhaustive list, in no particular order:
OH2HN     Altti
HB9BDM    Chris
VK3DNH    Chris
N7MJW     David
VK2JPR    Glen
VK2DSG    Les
VK2KNC    Norm
G3NDO     Pesi
N2QLQ     Steve
OH2BNS    Tomi
VK7KVB    Dick
ZL1BOE    Chris
ZL1BPU    Murray
ZK1DD     Des