It is a network of ham stations using CW Skimmer to automatically pick you call and measure its strength in dB compared to the noise level. For example, tonight I called CQs and had a few QSOs on the 20m band with 100W and my quite new delta loop antenna. These reverse beacon stations heard me:
|I had a QSO session on 20m at 9pm and these "robots" heard me.|
So, this hint is only for CW operators. Digimode operators have other options, like pskreporter.info and JT65 HF RB(=Reverse Beacon). SSB operators have miscellaneus net stream services for listening to their own voices...this is something I haven't tried yet.