QRP Labs QDX
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| Frequency | HF version: 80m, 60m, 40m, 30m, 20m. Hi-bands version: 20m, 17m, 15m, 12m, 11m, 10m. Select at purchase. |
| Bands | 5 or 6 bands (select version at purchase) |
| TX power | 5 W (5W at 9V supply (standard); can be built for 4-5W at 12V. Lower power on higher bands (~3.5-4W on 10m). Built for EITHER 9V or 12V at order time - do NOT run it from a 13.8V supply (it overdrives the BS170 finals).) |
| Modes | digital only: single-tone FSK modes (FT8, FT4, JS8Call, WSPR, RTTY, Olivia, most WSJT-X modes except MSK144) |
| Weight | 100 g (3.5 oz) - Approximate, without enclosure. Optional enclosure: 89×63×25 mm. |
| Connector | BNC |
| Year | 2021 |
| antenna | BNC |
| usb | USB-B (audio sound card + CAT control — single cable to PC) |
| ptt | 3.5mm (PTT output — for 50W PA kit or external amp, added Rev 3+) |
| dc in | 2.1mm power barrel connector |
| power req | 9 VDC (standard, for 5W) or 12 VDC (build-time option). NOT 13.8 V. RX ~100-150 mA. TX 1.0-1.1A at 9V for 5W (~0.7A at 13V). |
A complete digital-mode HF station for kit pocket money: add an antenna, power, and a PC. A built-in USB sound card and CAT control mean a single USB cable connects to the computer, with no external interfaces, audio cables, or level adjustments. A TCXO is included as standard. Single-signal transmission produces a cleaner signal than SSB rigs on digital modes. It has an embedded SDR receiver with 60-70 dB sideband cancellation and solid-state band switching with no relays. The pre-soldered SMD simplifies the build.
Digital modes only: no SSB, CW, AM, or FM, and no microphone or key input. It is built for a 9 V or 12 V supply chosen at order time and must NOT be run from a normal 13.8 V shack supply, which overdrives it. It has no SWR protection, so a bad match - including the brief glitch while an automatic tuner searches - can blow the cheap BS170 output transistors; feed it a resonant antenna or tune at low power. Power drops on the higher bands, you commit to the HF or hi-bands version at purchase, and the kit needs careful soldering. For CW or SSB, look at the QMX instead.
An inexpensive digital-mode HF transceiver kit that made digital HF very affordable. One USB cable to a PC puts you on FT8 with a clean single-signal transmitter. Many operators used it to get on HF digital for the first time.
The QRP Labs QDX is a digital-modes transceiver that, more than almost any other radio, made HF data operating cheap and simple. It is a kit (or a built unit) designed by Hans Summers that does one thing well: it puts about 5 watts of single-tone FSK - FT8, FT4, JS8Call, WSPR, RTTY and the like - on the air and receives them, while presenting itself to your computer as an ordinary USB sound card and a CAT control port. There is no microphone, no key, no SSB and no analog CW; it is digital only.
The clever part is what is not in the box. With most radios, digital operation means an external sound-card interface, audio cables in both directions, and fiddling with levels and VOX. The QDX has the sound card inside it, so a single USB cable carries both the audio and the rig control to the PC. Plug in an antenna, power, and that one cable, and you are on FT8. Its receiver is an embedded software-defined design with 60-70 dB of unwanted-sideband rejection, and a temperature-stable TCXO comes standard, which matters for narrow digital modes.
Two things are worth getting right. First, power: the QDX is built for either a 9-volt or a 12-volt supply - you pick when you order, and it is set with a couple of resistor values - and it should not be run from a normal 13.8-volt shack supply, which overdrives the little BS170 output transistors. Second, those same transistors are the radio's weak point: it has no SWR protection, so a bad antenna match, including the brief glitch while an automatic tuner searches, can blow the finals. Feed it a resonant antenna or tune up at low power. The transistors are cheap and replaceable, but it is a known failure mode.
It comes in a five-band low version (80-20 m) or a six-band high version (20-10 m), as a cheap kit or assembled for somewhat more, with an optional case; a monoband QDX-M extends the idea down to the 160, 630, and 2200 m bands. If you also want CW and SSB rather than digital alone, QRP Labs' QMX is the multimode step up, and the QCX-mini is the CW-only sibling. For getting on HF digital with the least money and the least fuss, the QDX is hard to beat.