VLF Radio

The lack of summer storms and static crashes makes winter a great time for monitoring the Very Low Frequency band (VLF). These are the radio frequencies below the AM band. Some lower and mid priced shortwave receivers cover this band but the sensitivity is poor and you will hear very little. A few high end receivers cover the band with adequate sensitivity but they are well beyond my price range.

The solution was to build my own VLF receiver. I began with my homebrew 80 meter direct conversion receiver. The salvaged WW2 variable capacitor with built in reduction drive and robust construction made this a great stable base to start with. I next built a VLF converter to bring the signals to the frequency range of the receiver. A low pass filter was added at the input of the converter to reduce unwanted signals.

It works great! On one evening I picked up several low frequency beacons,WWVB out of Colorado , LF AM stations (from Europe?) unidentified burst of sound possibly of a military origin, as they use some of these frequencies. (Low frequencies propagate via ground wave and are largely immune to the problems that would be caused my a nuclear strike. Also VLF waves will penetrate beneath the surface of the water and can be used to talk to submarines).