For many VLF enthusiast the ability to have a capable receiver that tunes down below 500 KHz with proper sensitivity has become more difficult.
The Icom R70, R71 and R75 series had excellent specs as well as the higher priced 9500 and were the rigs of choice.
Many modern HF transceivers for ham usage have the ability to tune this segment but the sensitivity is atrocious…more like 20 uV when we want to have 1uV if not better. The traditional in band spec for ham is 0.25uV. This is the same for the MW band where we do not want 50 Kw power stations overloading our ham receiver.
Dallas Lankford had great success modifying the Icom 703 for VLF use but it requires a steady hand and abikity to work with SMD components.
The Heathkit VLF convertor solves the problem by taking the received signal and placing it into the 80 m band where we can make better use of the receiver to recover the signals.
This was a simple test with 30 feet of wire and normally amplified or loop antennas are used but receiving the ZKF beacon in the late afternoon showed promise. Nighttime is the better time to listen and when signals noise and static is low. Remember these beacons use about 25 watts of power and are not intended to be heard more than several miles away from the airport or marine structure.
ZKF 335 KHz