WSPR Mini - the new small WSPR transmitter that can run from a LiPo battery.

Updated: May 23, 2019


I have now completed construction, testing and build of my latest WSPR Transmitter. I call it the WSPR Mini!


It is only 41x56mm in size (1.6 x 2.2 inches) and has the GPS antenna built in on-board. RF output power is 20mW. I designed it to run from a singe LiPo and from USB power. That means you can power it directly from you computer or you can get a LiPo battery and make it a very small and portable transmitter. It should be quite suitable to fly with a balloon or Kite etc. I also wanted this one to be really low cost to be a good starting transmitter and I think you will agree that 39 dollar for a WSPR transmitter with built in GPS is quite affordable.

The Mini runs the same firmware as my other WSPR transmitters and use the same PC configuration software. It has place for one user built low pass filter on board.

The new thing with this model besides being small is that I have designed in a few power saving features to extend the operation time when running from a battery. Only the GPS power-save is implemented at the time I write this. The rest of them will be implemented in upcoming firmware.

The power saving modes are: 1 Shutting down the GPS when not in use.

2 Shutting down the Si5351 PLL when not in use.

3 Putting the micro controller to sleep when not in use.

4 Holding of transmissions and going to sleep when battery voltage is below 3V

1S LiPo board.

To complement the Mini I have a daughter board with a 600mhLiPo battery and charge electronics that mates to the Mini and makes it truly portable.


Once mated together the USB port on the Mini becomes a charging port for the battery and and on/off switch on the LiPo board controls power to the Mini

The 600mAh battery should be good for 10 hours of continuous transmissions or about 30 to 40 hours of operation with pauses between transmissions blocks.

The LiPo board has two optional DC charging ports that accept 6V to 35V DC input for charging if it is used in a fixed setup or for example a solar cell is used to charge. Regardless if it is being charged from USB or external DC the charge current can be set by the user from 100mA to 1000mA. The protection and charge electronics will make sure it is not overcharged or over discharged.

Finally there is place to solder in a bigger battery in parallel if more capacity is needed.


I hope you will find the new product interesting. It should open up the field for experimentation with flyable transmitters and/or antennas. I'm quite eager to see if my small quad-copter can lift it with a 40m dipole, could be quite an interesting experiment. Finally, now that I have three different WSPR transmittters I have created a comparison and over-view of my WSPR transmitters on this page.

73 to you all from Sweden.


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