80m – 30m

Bands

5 W

Output

Frequency	classic version: 80/60/40/30/20 m; a high-band variant covers 20-10
Bands	80m, 60m, 40m, 30m, 20m (classic five-band; the high-bands edition trades these for 20-17-15-12-10)
TX power	5 W
Modes	CW, LSB, USB, AM, FM
Weight	140 g (4.9 oz)
Connector	SMA (an SMA-to-BNC adapter is the common first accessory)

Connectors

antenna	SMA (BNC via adapter)
cat	Micro-USB (CAT + firmware)
audio	onboard mic/speaker; TRS jacks for key and headset
power req	~5 W out at 13.8 V (typ. 500 mA TX; ~80 mA RX on MS5351-oscillator units, less with a genuine Si5351); famously makes ~0.5 W from a 5 V USB supply alone; Class E PA at ~85% efficiency

A five-band, five-mode HF transceiver the size of a soap dish: 90 x 60 x 30 mm, 140 grams - the pocket radio that made 'take a whole HF station hiking' a casual sentence Class E PA at ~85% efficiency is the engineering heart: ~5 W from 13.8 V at just 500 mA - and a party trick of ~0.5 W from any USB power bank Self-contained to an absurd degree: OLED, onboard mic, tiny speaker, SWR bridge, voltage/current metering, and the PTT button doubles as an emergency CW key Open source top to bottom under CC-BY-ND (DL2MAN's sandwich PCB + Class E LPF; PE1NNZ's transmitter/receiver concept and code) - and policed: the project maintains one approved supplier, publishes minimum benchmarks sellers must pass (4 W TX, 80% efficiency, -43 dB harmonics, -106 dBm noise floor), and firmware-BLOCKS the notorious 'black NanoRig' clones Micro-USB CAT control makes it a digital-modes companion despite the size - FT8 from a shirt pocket The authorized-vs-clone question is the whole buying decision: the official where-to-buy list names the approved stores; clones violate the no-derivatives license, miss the benchmarks, and get locked out of firmware updates

Strengths

The most radio per gram ever sold: five HF bands, five modes, real CAT control, and built-in metering in 140 grams for double-digit dollars - a complete station that disappears into any pack and sips current slowly enough for trail batteries. The open-source design means documentation, mods, and firmware life beyond any commercial radio's, and the QRP community's field literature is enormous.

Weaknesses

Five watts of SSB is a patience exercise (CW and FT8 are the radio's true callings), the receiver's strong-signal manners and audio are honest about the price point, the tiny controls reward small fingers, and the clone flood means an unverified purchase may not match the published spec - the famous efficiency depends on build quality the originals enforce and copies don't.

Verdict

The pocket miracle of the QRP era: not a primary station, but the radio that's actually WITH you - and at this price, the question isn't whether it replaces your rig but why your jacket doesn't have one yet. Buy authorized; the few dollars saved on a clone are repaid in mystery.

The (tr)uSDX is what happens when two of amateur radio's most inventive open-source designers - Manuel, DL2MAN, on hardware, and Guido, PE1NNZ, whose firmware lineage - from 2013 Raspberry Pi SSB experiments through the 2019 QCX-SSB hack to the uSDX concept - made software-defined QRP a folk movement - set out to build the smallest serious HF transceiver anyone had shipped. The result is a five-band, five-mode radio (CW, both sidebands, AM, FM) in ninety by sixty by thirty millimeters and 140 grams: OLED, microphone, a tiny speaker, SWR bridge, and voltage-and-current metering all aboard, with the PTT button moonlighting as an emergency CW key, the antenna on an SMA (the BNC adapter is everyone's first accessory). It is not a radio you pack; it is a radio you pocket.

The engineering heart is the Class E power amplifier running near 85 percent efficiency - about five watts out from a 13.8-volt supply at a mere 500 milliamps, with the celebrated party trick of producing half a watt from any USB power bank. Receive draw around 80 milliamps means a modest battery lasts an activation weekend. Micro-USB CAT control turns it into an FT8 machine despite the size, and the open-source design - schematics, firmware, the lot - gives it a documentation and modification culture no commercial radio matches. The same openness explains the marketplace flood of clones - and the project's unusually muscular response: a single approved supplier on the official where-to-buy page, published minimum benchmarks any seller must pass (four watts out, 80 percent efficiency, harmonics and noise-floor limits), and firmware that actively blocks the notorious 'black NanoRig' copies, which violate the license's no-derivatives clause. The buying advice is one word long: authorized.

The honest expectations: five watts of SSB through the onboard mic is a patience exercise best reserved for good conditions, while CW and digital modes - where the radio's efficiency and CAT control shine - are its true callings; the definitive field review logged eleven POTA contacts in twenty minutes while frankly documenting the S5-class noise floor, the front end's manners around strong signals, and a speaker that loses to birdsong. Remarkable and compromised, in that order, at this price. The classic edition covers 80 through 20 meters with a high-bands variant trading up to 20-through-10. As a first HF radio, a glovebox spare, a trail companion, or simply proof of what open hardware can do for double-digit dollars, the (tr)uSDX has no real rival - only clones.