Hoping to generate FST4W and WSPR signals on the LF band.

A device that generates FST4W and WSPR modes on various Amateur Radio bands.

FST4W on 136kHz...

"This Manned Experimental Propagation Transmitter (MEPT) uses the very popular Arduino Nano and Si5351A clock generator board to generate LF - 10 meter FST4W or WSPR signals. Frequency and time accuracy are maintained by ... using a GPS receiver." Gene Marcus W3PM GM4YRE

Wow! Timing was perfect. FST4W was released by the WSJT team and now this project became available. Thanks Gene. This build was of an elegantly clever design that suited my needs. My intent was to use this project as the front end to a new LF (2200m) PA, for both WSPR and the available number of FST4W modes, with the addition of enabling multimode transmissions. Phew!

The design includes frequency hopping, variable time sequences and the provision for the addition of using a Real Time Clock (RTC) for time keeping. I chose the simpler option of using my existing GPS receiver for timing and time keeping. I won't need the frequency hopping option. This will probably only used for single band operation (maybe...). So, this project will use an external low pass filter (LPF) at the RF output. If operating on a different band is required, I can change the LPF! Here are some photos of my build. A schematic is included in the links below. Enjoy. YMMV.

Front inside view

 Showing internal layout.

Rear inside view

 Showing internal layout.

RF amplifier

 Under the Si5351A board lies a 3    FET PA and relay.

Multimode display

 Displays shows Multimode active    on 137.577kHz.

QLG1 GPS Receiver

 This is built from a QRP Labs kit.

DSO RF output display

 Looking at the RF ouput after an     inline LPF. About 265mW.

Video showing display text changes and beacon going to transmit...

Video of my QRP Labs QLG1 GPS receiver front panel.

Useful Links


VK5FQ website
12/02/14 Start build of new website.


Steph - VK5FQ
Adelaide, South Australia,