Yes I agree, after a short while spherics can get very boring. I recommend this receiver for anyone interested in getting into this hobby. The VLF-3 kit which they provide is of very good quality and easy enough for just about anyone to build in a few quiet nights in the radio shack. As a matter of fact the Schumann resonance receiver which I use, found herecan easily be modified to receive the entire VLF band. I have been interested in natural radio for a good ten years now. These types of wide band signals are characteristic of natural EMF activity from Earth as well as our solar system and beyond. Spherics show up as wide band bursts when plotted on a spectrogram. These are the most common sounds heard on the VLF band and can be heard 24 hours a day. The snap, crackle, and pop sounds from lightning activity which one can hear on a VLF receiver, or AM and short wave radio for that matter are called atmospherics or spherics for short. One of the most popular uses for a VLF receiver is for listening to lightning strikes from around the world, and the interesting effects that this activity has on our atmosphere. You might be surprised to find out that it is not very difficult to build one. So how does one go about building a VLF receiver anyway? These two points form the basis for everything which follows. Here are some sample circuits to start out with.This band has the unique characteristic of having a portion fall within the audio frequency range of our ears.
The values of these components are most important. It consists of a combination of resistors and capacitors. Looking at the block diagram, the first stage starting from left going right is the high impedence low pass filter.
Lesser degree filtering does improve gain somewhat, but invites out of band signals. More antenna area or length means additional filtering will be needed. Undesirable signals become more evident as the antenna size is increased. The front end or input of the receiver is the most susceptible section to unwanted signals. The most important factor in VLF radio design is the use of low pass filtering throughout the circuitry. The circuit samples below are designed to work together one block section will connect directly with another section, providing it is put in it's proper place. Each section of the blocks are explained in detail. The picture here is a block diagram, which is very useful in looking at the overall structure of a good receiver design.
To construe how to go about building a receiver we must first get the basics down. A small antenna produces very little signal current for reception, however, a high gain, high impedance amplifier can make up for the difference.
A typical vertical antenna for VLF reception is usually less then 60 feet long some are even less then 10 feet.Ī resonant, full wavelength antenna is much longer than 60 feet. The reason for this comes from the ratio of actual antenna length to the resonant frequency wavelength. Jbl appĮ-Field receivers must use a very high input impedance to detect signals. Electromagnetic relates to the magnetic influence of a signal. Electrostatic pertains to the charge voltage or current wave of the signal.
The first step in building a receiver is to consider these questions. These circuit examples are optimized to design a receiver specifically for Natural Radio recording and listening. Some of the more advanced VLF receivers do use frequency conversion and digital tuning as well, we are just going to keep it simple here for now. The best feature of a VLF receiver is that it is already tuned for audio frequencies. Most radio receivers require complex frequency conversion to change and then demodulate the radio signal into an audio signal which is passed on to the amplifier stage to drive the speaker or headphones. The information here is most helpful to a person with a knowledge of electronic circuitry and fundamentals.