Note: This kit is now replaced by the Ultimate3 kit!


Version History
Kit photos
GPS compatibility notes
Builder's photos
Version k - operate QRSS and WSPR at the same time!

The ultimate QRSS Transmitter Kit is a new version of the  original Ultimate QRSS kit. This new version 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.


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 them near the PCB edge. If there is no revision printed, it means you have the 1st version (Rev 1).


Assembly instructions Board rev 1 click here!
Board rev 2 click here!
Operating manual

v2.01 click here!
v2.02 click here!
v2.02a click here!
v2.02k click here! special version, please see notes below
v2.03 click here!
v2.03k click here! special version, please see notes below
v2.04 click here!
v2.05/v2.06 click here!
v2.07 click here!

Low pass filter kit Download from page here!


Old original instructions, prior to separating the assembly and operating manuals, can be downloaded here.

Firmware Version History - please CLICK HERE

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

- 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

Other features:

- DDS-controlled output frequency (through-pin DDS module, no SMD soldering required)

- Plug-in low pass filter boards (available for 10 HF bands)

- 24-character 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


The kit contains the PCB, 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 108mm x 20mm. The main board is 43 x 48mm. The main board with the DDS module and LPF kit plugged on top, and buttons on the underside, will measure 50mm x 48mm x 32mm. The overall size of the assembled modules depends on what LCD mounting option you choose. Please see the manual for the options. With the recommended option 3 (LCD soldered to the board at right-angles), the overall size of the assembly will be 116mm wide x 56mm deep x 32mm high.

Kit photos (click for larger versions):

Kit version history:

Version Date Features
v2.00 22.Mar.2013 - Original kit firmware version for beta testers
v2.01 20.Apr.2013 - First official version
- Bug fix: after frame wait, frequency didn't return to correct frequency until tone changed
- Bug fix: WSPR did not work with any system clock frequency > 16,777,216 Hz
- New menu item "Inv. GPS" for triggering on a negative edge 1pps signal
- Impose limit of 200 seconds on the speed setting, to prevent arithmetic overflow
- Pressing right button during Run resets frequency and forces key-up
v2.02 02.Jun.2013
(only beta
was ever
- GPS: Prior v2.xx versions were very fussy about which GPS modules they would work with. The GPS interface is now returned as closely as possible to the original Ultimate (a.k.a. U1) kit operation. Note that there is no longer an "Inv. GPS" menu item, since the U2 will trigger off the correct edge by itself.
- DDS resolution on high frequencies: corrected the precision issue in the arithmetic, so now full accuracy shift steps are produced at any operating frequency. Removed the upper frequency limit of approx 42.5MHz, the full DDS range is now available New mode WSPR-15 is now supported, for experimental use on LF bands (8 times slower WSPR tones, 8 times closer together).
- New mode "FSK" which is a fast FSK mode for 10m beaconing, where the speed setting is interpreted in words per minute. The "FSK (Hz)" setting is now 3 digits (default "004" i.e. 4Hz) so that shift can be up to 999Hz. The "Inv. FSK" parameter has been discontinued in v2.02.
- “Heartbeat” indication on the display when the kit is GPS locked
- Baud rate setting extended to 6 digits, to support 115kbps rates for a particular GPS module
- GPS serial data is now set permanently to 8-bits, not configurable (suits all GPS modules anyway)
- Removed the DDS "reset" every time the frequency was updated, which caused the frequency to briefly go to zero before being updated to the new frequency. This improves output spectrum.
- Put a "stop" on the cycling through characters when editing the Message (and other text) parameters, by holding down the right button.
- Moved the "Time" parameter to the start of the menu, when the kit is in WSPR mode, because the Time parameter is what you would most commonly want to adjust, when operating in WSPR mode without a GPS to regulate it. In other modes, "Time" still comes right at the end of the menu.
- CW, FSKCW, DFCW, QRSS and FSK modes can support the '/' character in the message
- Bug fix (cosmetic only): When setting the time, the 10 minutes digit incorrectly allowed numbers >= 6. So it was possible to set a time such as 15:89.
- Bug fix (cosmetic only): If you went back in to the time parameter to edit it a second time immediately after finishing the first edit, the display was overwritten incorrectly, with the system clock frequency display.
- Bug fix (cosmetic only): If using FSKCW mode an 10 second dit speed (for example), in the interval between frames the LCD display did not have space to show the seconds digit of the clock. The "Waiting" screen has now been changed. It now only shows the time and the minutes to wait until. E.g. "15:43:21 >50" means 3:43pm and 21 seconds, and the kit is waiting for minute 50 to start the next frame. The "Waiting" screen also shows the GPS heartbeat if a GPS is connected and GPS lock is successful.
- Bug fix: In FSKCW mode, the GPS frequency stabilisation operating in the waiting period between messages, only worked the first time after cycling through the menu. Subsequent waiting periods did not perform the calibration because the kit was always in key-down (transmitting the low tone between messages).
- The default speed setting is changed to 006 which is a better default value The mode message "CW Ident" when transmitting the CW callsign identifier is replaced with “CW”
v2.02a 15.Jun.2013 - In FSK/CW, key is always down following a message completion, until the start of the next frame. If using a GPS, key-up occurs during the last 13 seconds before the next frame, when calibration occurs
- In Hell modes, the frequency is now dropped to 6.25MHz during key-up in a space character or between message transmissions
- Bug fix: factory reset of speed was to 003, should be 006
- Bug fix: cosmetic correction to the GPS "heartbeat" feature
v2.03 01.Jul.2013 - GPS: Improved handling of different varieties of GPS module
- Bug fix: 1's digit of the calibration of the 125MHz oscillator frequency was incorrectly set to the same as the 10's digit in the binary to decimal conversion
v2.04 16.Sep.2013 - More robust handling of GPS signal outages, keeps time from 20MHz osc.
- DDS frequency is temporarily set to zero on key-up: removes carrier leakage on key-up
- New “Transmit” mode allows keying by a morse key, turning the kit into a transmitter
- v2.04 merges the functionality of v2.03 and v2.03k, allows two modes transmitted sequentially
- Provision of “Fine FSK” mode in which the frequency step is 0.029Hz
- Multiple GPS modes, for 1pps level change, positive and negative edge triggering
- v2.04 always uses the Callsign setting for WSPR (never the contents of “Message”)
- The 500Hz lower limit on frequency is now removed
- Lower limits on sys. freq. and ref. freq. settings removed saving code space
- Press right button keys PA in any mode during wait between messages, for tuning
v2.05 17.Oct.2013 - Removed “CW Ident” parameter; replaced by additional Mode 2 / Freq. 2 setting.
- Added new mode “CW ID” for sending the callsign identifier at 12wpm
- Added “ParkMode” parameter and “ParkFreq” parameter, to control DDS state during key-up
- Bug fix: Custom characters would not work if any “Mode” setting was other than FSKCW
- Bug fix: Factory reset feature was broken in v2.04
- Bug fix: cosmetic issue with setting Time parameter in v2.04, screen filled with several 0's
v2.06 03.Nov.2013 - Bug fix: GPS calibration was inaccurate if immediately after a Mode 1 Hell transmission
v2.06a 07.Nov.2013 - Bug fix: calibration error if left button pressed to enter meny system during a calibration.
v2.06b 09.Nov.2013 - Bug fix: ParkMode and ParkFreq parameters could sometimes get corrupted.
v2.06c 27.Nov.2013 - Bug fix: Location and Time should not be set until GPS validity flag is 'A'.
v2.07 13.Dec.2013 - Huff Puff GPS calibration method. Two new parameters "Cal Time and Cal HP". Click HERE!
- Bug fix: Park Mode 1 (offset) now offers shifts up to 61kHz.


GPS Compatibility notes

The following modules are known to work with the kit. The table gives a source if known, and the appropriate "GPS Baud" setting to use in the kit, to suit the GPS module's default output configuration with the kit.

Please note that some inexpensive GPS modules such as the VK16E using the Sirf III chipset, have a somewhat inaccurate 1pps signal. A method to cope with this has been devised and released in firmware version v3.01. Using the new method, the calibration accuracy is very good. You can read more details here.

Model Antenna Source "GPS Baud" Comments
Trimble Silvana ACM Built-in dpieshop 09600,01,1,8 Uses Trimble Condor C1919A GPS module; requires 3.3V regulated supply.
Works only with v2.03 and above.
MTK3339 Built-in Adafruit 09600,01,1,8  
Reyax UP501 Built-in eBay, GBP 17 09600,10,1,8 Requires 3.3V supply. Note different "GPS Baud" setting. Do NOT use pull-up resistors!
EM-406A Built-in Sparkfun or Expansys or Proto-pic 04800,01,1,8 Works with firmware v2.03 and above.
May need to use 10K pull-up resistors from 1pps and Serial signal to +5V


Builder's photos

Philip, G4JVF - 20m WSPR

Philip was the very first order of the Ultimate2 and had it built, beautifully boxed, operational on WSPR on 20m all within a matter of hours. See the great inspiring photos below! Peter writes that he:

- Put it in a box with socket for GPS module and switchable PA supply (5v or 9v)
- Not used the on-board LP filter as I’ve built a switchable external filter box to give me quick band change.
- Put sockets in the spare PA positions so I can drop in an extra FET without taking the board out...

Peter, G4FYY - WSPR on a Ring

Here's a picture of Peter's coffee table station, using a coaxial ring antenna. Peter and 25 more members of the Crawley Amateur Radio Club (UK) are building the Ultimate2 as a club construction project. As you can see from the map (30m, 5'th May 2013) Peter's signals are certainly getting out fine! Antenna details are available at the links below.

Keith G6NHU - Keith wrote a blog about his experiences with the kit, see here.

Len KA7FTP - very nice job!

Version 2.02k/2.03k - Operate WSPR and QRSS at the same time!

Note: from version v2.04, the "k" version was merged back into the main firmware version.

This is a special experimental version, with changes requested by Keith Maton G6NHU. The "k" in the version name is in fact, for "Keith", who wanted to run WSPR and QRSS modes at the same time. So this version always transmits one WSPR frame, then follows this with the message of your choice, in the mode of your choice. Different frequencies can be set for the WSPR message and the QRSS message.

This version is built on v2.02/v2.02a, with the following main differences:

a) Always sends a WSPR frame, followed by your choice of message in a QRSS mode

b) In order to provide code-space for these modifications in the 16K program memory available on the microcontroller, this version no longer supports any Hell modes, or the WSPR-15 mode.

c) Two frequency settings are available, one for the WSPR output, and one for the QRSS mode output

d) Free-running transmission is now not possible: you MUST choose a valid WSPR frame and Start. 10 minutes is strongly recommended, and should provide enough space for the 2-minute WSPR transmission and your QRSS-mode Message transmission.

e) Enter your call in the “Callsign” menu setting, this is now used only for WSPR. The “Message” setting is used for the QRSS mode transmission.

This version has its own special operating manual, please CLICK HERE!.

Ordering statistics

The following chart shows the number of LPF kits ordered to date for each band. Many people order one Ultimate2 kit with multiple LPF kits so that they can change band.