Most of the energy radiated by such VLF/LF transmitters is trapped between the ground and the lower ionosphere, forming the Earth-ionosphere waveguide. To radiate electromagnetic waves efficiently, one needs an antenna with dimensions on the order of a wavelength of the radiation, which suggests that VLF/LF transmitter antennas are very large, typically many hundreds of meters high. The use of VLF/LF subionospheric propagation as new methodologyР”Р„ number of nations currently operate large VLF/LF transmitters primarily for navigation and communication with military submarines. As the result of research during the last ten years, it has been a consensus that the ionosphere is unexpectedly extremely sensitive to the seismic effect (e.g., Hayakawa and Molchanov, 2002), which is the topic of this review.Р”Сћ.1. The electromagnetic method for earthquake prediction can principally be classified into two categories: The first is the detection of radio emissions from the hypocenter, and the second is to detect an indirect effect of earthquakes taking place in the atmosphere and ionosphere by means of the preexisting radio transmitter signals (we call it РІР‚Сљradio soundingРІР‚Сњ). While the mechanical effect provides us with the 0th-order (or macroscopic) information on the lithosphere, the higher-order (microscopic) information can only be tackled by electromagnetic effects. Then, we have had a new wave of the measurements by means of electromagnetic effects, and we have accumulated a lot of evidence that electromagnetic phenomena take place in a wide frequency range prior to an earthquake (e.g., Hayakawa, 1999 Hayakawa and Molchanov, 2002). The conventional earthquake prediction has been based on the measurement of crustal movement, but this kind of mechanical measurement has been concluded to be not so useful in the short-term earthquake prediction. The situation for the short-term earthquake prediction seems to have drastically changed during the last ten years since the Kobe earthquake in 1995. However, in sprite of the essential importance of (3) short-term (of the order of a few months to a few days) earthquake prediction, it has been far from realization. Due to the enormous advance in seismogology, seismic geology and geodesy, we notice significant achievement in (1) long-term (of the order of a few hundred years) and (2) medium-term (of the order of hundreds to a few years) prediction. Generally speaking, the earthquake prediction can be classified into three, depending on the time scale we are concerned with. In order to mitigate the earthquake disaster, the earthquake prediction is of primary importance. have indicated how large the earthquake hazard is. In this review we deal only with earthquakes, and the media news for the latest, huge earthquakes such as Japanese Niigata earthquake, Indonesia Sumatra earthquake etc. There have been a wide variety of natural disasters including abnormal meteorological effects (abnormal climate changes), earthquakes, volcano eruption, etc. The converter is working quite well with the Belka-DX at opening up a new part of the radio spectrum.1.РІР‚С“Introduction to Seismo Electromagnetics The new 630m (472-479 kHz) band is also covered. The intended frequency range of the converter is that of non-directional beacons, operated near airports around the country. At the time, I wasn't interested inР”Р„M BCB DXing, but now, even though I can easily receive strong local AM stations, I wonder what weak stations I might be able to hear that I can't with the components in place. I added the filter components to my converter but I may remove them. So to my knowledge, the Jackson Harbor, if not the only such converter, is almost certainly the least expensive. K1EL started to offer a converter kit but it never got off the ground. I never heard any submarines with it but, years later, I would hear them very clearly - no radio needed. Their ads enticed me with the ability to 'hear submarine communications'. Years ago Palomar Engineers sold a VLF-to-80m converter and I had one as a teen in the late 70's. No case is included - I bought mine at Fry's.remember them? RIP.

The converter is only $14 ($17 with filter components designed to reduce AM broadcast QRM). So a 200 kHz signal becomes 10.200 MHz, receivable on any 30m receiver. This LO signal is mixed with the incoming LF signal from an antenna and their sum is the output. The heart of the converter is a 10 MHz (or 4 MHz - both crystals are included) oscillator. With the Belka-DX only covering the upper 200 kHz of the AM broadcast band I decided to see what the outcome might be if I paired it with one of the first kits I ever built - a VLF converter from Jackson Harbor Press.

Vlf receiver review