Underground station (-80 m.) Sil de las Perlas, Valporquero cave, León,
(Yaesu FT817ND, 0,5 w RF power, WormAnt antenna, 80 m. band)
Two surface stations:
If you want explore the soil ants performance this simple model it's for you!
Only needs a ATU1), a balum and some meters of conductor. The details in the images and a link for download the full article at the end .
A simple but effective RX antenna for 40 meters HAM band. S/N RX improvement. Click on image for full article.