Kit photos
DDS testing/adjustment

The current version of the kit is the Ultimate3S, which was launched in January 2015.

The Ultimate3 QRSS/WSPR Transmitter kit was produced from November 2013 to December 2014. It was the third version in the "Ultimate" QRSS/WSPR kit trilogy. It can produce QRSS, Hell, WSPR, Opera and PI4 slow-signal modes anywhere from audio to 10m and above. Plug-in LPF filters are available for all 12 HF/MF/LF bands. The U3 firmware is suitable for use in both the U3 and U3S kits.

Please also see the original version Ultimate QRSS kit and Ultimate2 QRSS kit pages. The new "U3" version is similar to the "U2" in terms of functionality, but has a much nicer 16 x 2-row Standard LCD, with blue backlight. This LCD has a 0.1-inch pitch connector, so the U3 is easier to build than the U2 (with its 0.05-inch pitch LCD connector). The new PCB has the same size as the LCD module, and is bolted to it using hex spacers. It therefore also produces a nicer mechanical assembly than the U2.

The Ultimate3 QRSS Transmitter Kit comes with a pre-assembled AD9850 DDS module, and plug-in low pass filter modules which are also available separately for any band. The kit can transmit on any frequency from audio (500Hz) to over 40MHz, and changing bands is a matter of plugging in the appropriate low pass filter kit to attenuate unwanted harmonic output.

The kit supports the following modes:

- QRSS mode (plain on/off keyed slow CW)
- FSK/CW mode (frequency shift keyed slow CW)
- DFCW mode (dual frequency CW)
- WSPR mode (Weak Signal Propagation Reporter)
- WSPR-15 experimental WSPR mode with 15-minute frames
- Opera modes (8 speeds)
- PI4 beacon mode
- Slow-Hellschreiber (frequency shifted slow-Hell)
- Full-speed Hellshreiber
- Half-speed ("DX") Hellshreiber
- CW (plain CW)
- FSK (0-999Hz shift, fast-speed FSK CW)
- Customisable FSK patterns
- manually-keyed CW/FSK transmitter

Other features:

- DDS-controlled output frequency (through-pin DDS module, no SMD soldering required)
- Plug-in low pass filter boards (available for 10 HF and 2 LF bands)
- 2-row by 16-character blue back-lit LCD + two-button user interface
- User-programmable (callsign, message, speed, FSK, mode, etc.), settings stored in EEPROM
- GPS interface, for locking the frequency, timing and location information
- On-chip generation of WSPR encoded message (no PC required)
- WSPR maidenhead locator can be generated from GPS-derived latitude/longitude
- Selectable “frame” size, for stacked QRSS reception
- Plain CW callsign identifier at selectable interval
- Produces 150mW RF output on 30m (lower output on higher frequency bands)
- Higher output power by additional PA transistor and/or higher PA supply voltage


Printed instructions are not supplied with the kit! You need to download them here. You need THREE manuals, and to choose the version appropriate to your PCB and firmware version: the Assembly manual, the Operating manual, and the Low Pass Filter kit manual. The Revision 2 PCB's have "Rev 2" printed on their top side. Similarly for Rev 3 PCB (all kits shipped after 07-Mar-2014 are Rev 3). If there is no revision printed, it means you have the 1st version (Rev 1). Many thanks to Roberto IZ7VHF for the fine Italian translation!

Assembly instructions PCB rev 1 click here!
PCB rev 1 in ITALIAN click here!
PCB rev 2 click here!
PCB rev 3 and rev 4 click here!
Operating manual Download from firmware page!
Low pass filter kit Download from page here!


Version upgrades can be purchased at QRP Labs or you can upgrade your own firmware using the .hex and .eep files from the Yahoo forum.

Firmware Version History - please CLICK HERE

The kit contains the PCB, back-lit blue LCD, programmed microcontroller, pre-assembled DDS module, all board-mounted components, and a LPF kit for one band. Download the instruction manual using the link above. The PCB is quite compact and care is required in the construction. A rich array of functionality is provided by the design; please read the instruction manual to understand the facilities provided. Builder modifications will be shown on this page as they are developed!

Dimensions: the LCD module is 80mm x 36mm. The main board is 80 x 37mm.

Kit photos (click for larger versions):

Reviews and blog entries

Nice review by Antonio EA1CDV Spanish English translation by Google
Review part 2 by Antonio EA1CDV Spanish English translation by Google
Ultimate3 kit review by Michael DL2YMR German English translation by Google
LPF kit review by Michael DL2YMR German English translation by Google
472kHz WSPR and SSB by HB9ASB German English translation by Google
Ultimate2 kit review by Claudio I1RFQ Italian English translation by Google; this is about the U2 but still relevant to U3.
U3 blog by Claudio I1RFQ Italian English translation by Google
U3 kit review by Steve G4HSK English  
U3 Whispering 14,000km, by Hajo DL1SDZ English  
WSPR'ing 411,200km per Watt, Hajo DL1SDZ English  
Sverre LA3ZA reviews the Ultimate kits English  
Lex PH2LB's build log, nice photos of his work! English  
Blog posting about Simon G4TJC's U3 running with GPS English  
Review by Karen RA3APW (freq. stability & Glosnass) Russian English translation by Google
eHam review (Paul VK4APN) English  

DDS testing and adjustment

All AD9850 DDS modules supplied with the Ultimate3 kit are individually tested and adjusted to ensure correct and stable functioning suitable for use in a QRSS/WSPR transmitter, and to adjust the comparator threshold potentiometer which is necessary for the AD9850 comparator to produce a squarewave output for driving the Class-D PA in the Ultimate3. This testing/adjustment procedure is descrived in this separate page, read more...

More photos...

These photos show a working U3, complete with attached relay-switched Low Pass Filter board, available for GBP 9. The relay-switched LPF board can have up to five additional LPF's plugged in, permitting the U3 to sequence between 6 bands (including the LPF on the main U3 board). Note that my photos show NO additional LPF's plugged in (as I only have one built LPF here right now).