Q15X25 is a packet modem with a KISS/AX.25 interface designed for HF transmission of AX.25 packets and TCP/IP using Automatic Repeat reQuest (ARQ) and forward error correction (FEC). It operates like a packet radio terminal node controller (TNC). Its 15 tones are separated by 125 Hz, each QPSK modulated at a symbol rate of 83.33 bauds to provide a raw data rate of 2500 bit/s in an occupied bandwidth of 2000 Hz. Its emission designator is 2K00J2D. Signals can be found at 14 109.5 kHz upper sideband. 

A sample of the modulated signal is available.

Q15X25 was developed by Pawel Jalocha, SP9VRC, for the Motorola DSP56002EVM digital signal processing evaluation board in the late 1990s. Jolocha also developed MT-63.It has been ported to LINUX PC by Tomi Manninen, OH2BNS.This protocol has been implemented on Windows PC sound card.

This is still an experimental mode. Additional details toward an updated version are welcome and should be sent to w4ri@arrl.org.

Paul L. Rinaldo, W4RI
July 19, 2005