Design of VLF Receiver to Detect Solar Flares and Gamma Ray Bursts

Here is an updated version of the simple VLF receiver first described in the April SID Supplement of the Solar Bulletin. The design is based on the principle known to all amateur radio operators that the most important part of a transmitting or receiving system is a good antenna and a well matched transmission line.

We met the first requirements by building a hexagonal loop antenna that measures around 1meter (59 inches) across the diagonals and winding it with 24 turns of # 14 stranded copper wire & the second requirement by eliminating the transmission line altogether. The receiver is built right on the loop antenna so there is no need for a transmission line between the antenna and the receiver. After the signal is amplified 900 times it is sent over a transmission line consisting of ordinary 4-wire telephone wire to a recorder driver. There is no need to match this transmission line to the recorder driver because the signal has already been amplified 900 X. There is plenty of signal to make up for any lost on the transmission line. We call this a “Loop Antenna Receiver” because the loop is the receiver. It is the LC resonant circuit for the receiver and owes its success to being a large high-Q loop with much greater aperture than small

loop antennas usually used with Sudden Ionospheric Disturbance (SID) receivers. The low resistance of the #14 wire gives the loop a high Q, about 400 compared to about 20 for small loop antennas wound with #26 wire that are used by most SID observers. The receiver has a pass band of less than 500 Hz which compares favorably with other SES (Sudden Enhancement Signal) receivers in use today.

This loop antenna receiver is meant to be located outdoors so it can be placed as far as possible from electrical wiring which is the source of most if not all of the interference that plagues SES receivers. Below the chart is a simplified diagram of how to hook the parts of the receiver together. It is not necessary to put the receiver in a weatherproof box.


Fig. Fundamental Circuit Diagram of VLF Receiver to Detect Solar Flares and Gamma Ray Bursts



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