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WSPR Transmitters overview and comparison

Three transmitters - one software.

I currently manufacture and sell three different WSPR transmitters.
They run the same firmware and they use the same PC configuration software. 
The firmware is open source and the electrical schema is available on all transmitters to give you the greatest ability to experiment, expand, modify and play around.
Although they are well suited for experiments they are at the same time stable and well tested.

With the built in GPS that always have the correct time it means that the transmitters are ideal to run unattended for a long time. The GPS also means that you don't have to know your position, the GPS will keep track for you.

Regardless if you want a transmitter that is small, expandable or something that is ready to put on the air you should be able to find a transmitter that fits your needs.

Here are the three transmitters and their characteristics.

  1. WSPR Mini The Mini is designed to be the lowest cost, lowest  power small TX for portable use.
    It weights only 21gram so should be suitable to fly on a balloon or Kite, Quad copter etc.
    To minimize current consumption there are a couple of power savings mode implemented in hardware and software that conserves power between transmission passes.
    The RF output power is about 20mW.


  2. WSPR XP (Formerly LP1)  The XP is designed to be an experimental platform where there will always be room for expansion and experimentation. It comes with space for a single low pass filter but can be expanded to four low pass filters.
    It has a very good temperature compensated crystal oscillator for precise and low drift output frequency.
    It comes with an external GPS antenna with 3m cable.
    The RF output power is 200mW to 300mW depending on band and filter model used.


  3. WSPR Desktop The Desktop is the nice boxed ready-to-put-on-the -air model.
    The aluminium box is black with a block diagram printed on top to give it a technical look as well as being practical as it shows you the different input/output ports.
    It has the same great data from the WSPR-LP1 and the same accurate TCXO reference.
    It has four internally switched low pass filters and comes in three models that covers different portions of the HF band.
    Plug in to a PC to set up your call sign, and you are good to go!
    It comes with an external GPS antenna with 3m cable and a 1m USB cable.
    The RF output power is about 200mW.

The Transmitters

The receive performance for Hardware version 1 and 2 is the same but the internal construction differs somewhat . The major difference is that version 2 removes the switches, buttons and jumpers to set the  receive frequency and to calibrate the reference oscillator. In version 2 hardware this information is instead read from EEPROM.  

WSPR TX Models2.jpg

For more information on each transmitters see the documentation page for the specific model.

  1. WSPR Mini documentation page.

  2. WSPR LP1 documentation.

  3. WSPR Desktop documentation page. 

The Software

The PC Software runs on PC with Windows and can configure and control all three models.
It is currently in Beta and gets updates regally, it is pretty stable but has some little  quirks and needs a bit more polish before I call it version 1.0. 
It communicates with the WSPR transmitters using a serial port and a set of commands. The command set is documented so users can write their own software if they want to.
KB9RLW has written an alternative configuration software that runs on Linux

Skärmklipp 2019-07-06 14.34.51.png

Finally let me mention that all my WSPR transmitters are frequency calibrated by myself against my in-house Rubidium frequency standard before delivery.
The calibration data is stored in EEPROM and can be redone by the user if needed in the future.
This calibration ensures that you will have one of the most accurate transmitters on the bands.

The exception is the Mini, it runs from a simple 10ppm crystal so it will drift a little.
The LP1 and Desktop model on the other hand use a very high quality temperature compensated oscillator as reference, these models are often accurate down to a single Hertz. 

I hope you will find a model that fits your needs and that it will serve you well.

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