QRP Labs’ August 27 update turns the QMX and QMX+ into more capable stand-alone beacon platforms, adding RTTY and filling out the remaining Ultimate3S modes. A newer maintenance build is already the one to install.
QRP Labs firmware 1.04.008 is a small release with an unusually interesting payoff for beacon-minded operators. It adds RTTY to Virtual U3S, brings in the remaining modes from the hardware Ultimate3S, and fixes a frame-setting limit that could get in the way of longer transmission schedules.
Update note, August 30, 2026: QRP Labs has already posted firmware 1.04.009. Its release note says 1.04.008 transmitted WSPR 250 Hz low; 1.04.009 corrects that error. Operators updating now should use the latest official build, while treating 1.04.008 as the feature release that introduced the changes discussed here.
RTTY moves inside Virtual U3S
The headline addition is RTTY generation within Virtual U3S. That distinction matters: QMX could already work with computer-generated digital audio in its normal Digi mode, including RTTY from software such as fldigi. Firmware 1.04.008 adds RTTY to the radio’s stand-alone Virtual U3S beacon environment instead.
In practical terms, the feature is aimed at scheduled, unattended-style transmissions configured on the radio, rather than ordinary keyboard-to-keyboard RTTY operation through a computer. QRP Labs also notes that RTTY was not available in the original hardware U3S, so the “virtual” implementation now goes beyond a literal reproduction of the older beacon transmitter.
Virtual U3S now covers the remaining U3S modes
Virtual U3S first appeared in the 1.04 firmware line as an attempt to reproduce the Ultimate3S QRSS/WSPR beacon transmitter inside QMX and QMX+. The mode set then grew in stages. Version 1.04.006 added WSPR15, CW, CW ID, FSK, FSKCW, QRSS, DFCW, Slow Hell, Hell, and DX Hell. QRP Labs says 1.04.008 adds all remaining U3S modes, along with the new RTTY option.
| Release | Virtual U3S change | Operator takeaway |
|---|---|---|
| 1.04.000 | Virtual U3S introduced | Ultimate3S-style beacon functions begin moving into QMX/QMX+. |
| 1.04.006 | WSPR15, CW, CW ID, FSK, FSKCW, QRSS, DFCW, Slow Hell, Hell, and DX Hell added | The stand-alone mode list becomes much broader. |
| 1.04.008 | Remaining U3S modes plus RTTY; frame limit fixed | Virtual U3S reaches feature-complete U3S coverage and gains a mode the physical U3S lacked. |
| 1.04.009 | Corrects 1.04.008 WSPR frequency by 250 Hz | Use this or a later official build for WSPR transmission. |
The frame fix is less glamorous, but useful
Version 1.04.008 also fixes a Virtual U3S Frame parameter that could not be set above 30. The frame value governs the repeating schedule used by the beacon system. Removing the artificial ceiling gives operators more room to build longer or less frequently repeated sequences. Exact settings and timing behavior should be taken from the current Virtual U3S manual, especially when mixing modes or coordinating transmissions to UTC time.
What operators should check before transmitting
- Install the current release. Because 1.04.009 supersedes 1.04.008 with a WSPR frequency correction, download the newest firmware from the QRP Labs QMX page.
- Read the separate Virtual U3S manual. QRP Labs published manual revision 1.04.008a on August 28, covering firmware 1.04.008a and later.
- Review every band and schedule entry. Confirm frequency, mode, message, frame timing, callsign, locator, and power before enabling unattended sequences.
- Use the right output filtering. As with any multiband transmitter, the configured band and connected low-pass-filter path must match the intended transmission.
- Stay within local rules. Beacon, automatic-control, identification, duty-cycle, and band-segment requirements vary by jurisdiction and license privileges.
Bottom line
Firmware 1.04.008 is notable because it makes Virtual U3S substantially more complete and adds stand-alone RTTY that the original U3S never offered. That gives QMX and QMX+ owners another reason to explore the radios as compact beacon platforms, not only as CW, Digi, and SSB transceivers.
The immediate caveat is equally important: 1.04.008 is no longer the newest build. Use 1.04.009 or later so the WSPR offset correction is included, and verify a new configuration into a dummy load before putting a repeating schedule on the air.
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