top of page
"CW Flea" transmitter

"CW Flea" transmitter

SKU: 1038

The CW Flea transmitter is a CW transmitter for 40m, 30m and 20m band with 300mWatts of power.


Some quick features:

  • Just a transmitter, it is intended to operate with a receiver and has automatic switching of antenna between them

  • Is powered from 8 to 15V.

  • Open source software and Open Hardware.

  • Band switching with push button 40m, 30m, and 20m


This little CW transmitter came to life through a colaboration with YouTuber Kevin Loughlin

It is very simple and uses Kevins clever method of tuning without using a display or tuning knob, the tuning is instead a side tone that can be heard in the receiver (not included).

It comes assembled and programmed, ready to operate.

A suitable box for it can be 3D printed and Kevin has published files for it, check out his YouTube channel for more info.


It has a 3.5mm jack for a CW Key, a BNC antenna connector and a SMA output to connect to your receiver.

When not transmitting the antenna is connected to the receiver.

To operate it you will tun to the frequency or CW station you want to operate and use the tune button on the CW flea until you can hear the side tone appear in the receiver, once they match you are ready to start keying.

When you key the receiver output is connected to ground and the CW flea will use the antenna for transmission.


Due to being open source you can adopt it to to other stuff if you want like a CW, QRSS, Field Hell, WSPR or other digital mode beacon.


The built in low pass filters give more than 50dB suppression of overtones so it will compliant world wide.

The oscillator is an si5351 with a stable 1.5ppm TXCO so you will always be on and stay on frequency.

The power output is 350mW+ on the 40m and 30m band and 250mW on the 20m band - hence the name :-)


It comes with the male DC plug to be soldered In to a suitable cable and power source.



The connection to the receiver is from a female SMA connector, there are short cables in the store if you want to convert to different connector. I recomend the Male SMA to Male BNC pigtail cable with SKU number 1039


Documentation page here:

    bottom of page