My very low power transmissions on longwave

Last night I made successful radio test transmissions on 137.7KHz, 2190m band, using only 3.5W transmitter power. My signal was received, ( screen capture below ), at a distance of 17Km. The signal strength suggests that 2-way communication at this power level would be possible over a much longer distance. The vertical streaks are probably static crashes as a thunder storm was active in the vicinity.

My setup was my own-design PIC controlled DDS and the TDA2030 AF amplifier featured on 22 February. 

It is unfortunate that amateur radio activity on the 2190m band is so low, as it is possible to enjoy communicating on this band with a minimal setup, as I have just shown.