1. Overview of features
QMX is a high performance, five-band multi-mode 5W QRP transceiver kit, which implements a
sophisticated SDR receiver in a 168MHz 32-bit ARM Cortex M4 microcontroller (STM32F446).
Most of the features are implemented digitally in firmware, and the feature set is continuing to be
expanded by ongoing firmware development. Please refer to the later section on planned future
functionality. This section provides a brief summary of the features to explore and enjoy.
QMX is highly portable
The small size and very low receive current consumption (as low as 80mA) are key features of
QMX, making it an ideal transceiver for portable operations including SOTA and POTA activations.
QMX is a standalone CW transceiver, or a Digimodes modem
You can use QMX on its own, plugging in earphones, power supply, paddle and antenna and
operating CW; or, you can connect it to a PC with a single USB-C cable, to provide CAT control
and Digital audio to the PC and use it with WSJT-X or other programs for single-tone FSK digital
modes (not suitable for PSK31 and phase shift modes until SSB is implemented).
Synthesised VFO with rotary encoder tuning
The VFO is an Si5351A or MS5351M synthesiser chip, configured by the microcontroller. A rotary
encoder tunes the VFO, with a variable tuning rate. The radio includes two VFOs, A and B. You
can swap from one to the other, copy the contents of the active VFO to the inactive one, or
operate Split (Transmit on VFO A, receive on VFO B). There is also a RIT mode offering a receive
offset of up to +/- 9,999Hz. The CW offset is also adjustable, and CW-R (sideband swap) mode is
supported.
Memory features
There are 16 frequency presets for your favourite operating frequencies. Each frequency preset
can be edited in the configuration menu, or loaded/saved into/from the currently operating VFO.
Message mode
The firmware supports storage of 12 messages. Each of these are 50 characters long. A single
button click shows the list of messages to send. Message sending can be configured to send just
once, or a configurable number of times, or indefinitely repeating. The interval between
transmissions is also configurable. The message feature can be useful, for example, for setting up
a repeated CQ call with a pause between repeats, during which you can listen for any answers. As
soon as you touch the key the message sending is canceled. When message sending is in
progress an ‘M’ character appears near the top right of the display.
CW Keyer
Operation with a Straight key is possible, but the firmware also includes an Iambic keyer, for
connection of a paddle. The keyer can be configured to operate in Iambic modes A or B, or
Ultimatic mode. The keyer speed is variable via a single button press during operation.
Full or semi break-in
With its solid-state, microcontroller operated transmit/receive switch, the radio can operate cleanly
in full break-in “QSK” mode, or if you prefer, semi-break in.
QMX operang manual; rmware 1_00_012 4
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