Welcome to SID-GRB@home! This web page records my attempts to build a simple VLF receiver that can detect Sudden Ionospheric Disturbances (SID) and that are caused by x-rays from the sun (solar flares) and by x-rays from Gamma Ray Bursts (GRB) from the edges of the universe. See for latest page updates.
When I built my first SID receiver antenna to Casper Hossfield's April 2002 specifications (24 turns, #14 wire, 1.5m diameter), I found that it took about 0.024 ufd to tune it to 24 khz, and not the 0.0176 ufd specified in the April 2002 SID supplement. I asked Cap about this and he said not to worry, if it works, then fine. I was using 2% capacitors and hoped to avoid some of the problems with tuning the loop, but not so.
I think I have found a free program that accurately computes antenna specifications. RJELOOP3.EXE computes the parameters of receiving, multi-turn, square, loop antennas, ELF to HF. This DOS program can be downloaded here There are 5 inputs, and here are my calculations that you should double check.
RJELOOP3.EXE Program Inputs:
We need to compute the side (L) of a square antenna that has the same area (A) as our hexagonal antenna with 1.5 meter maximum diagonal (d). From high school trig I compute as follows (better check me on this!):
d = 1.5 meters = 1500 mm
A = 6*SQR(3)*d*d/16 = 6*SQR(3)*1500*1500/16 = 1461417.9 mm2
L = SQR(A) = 1208.9 mm
You can find standard wire diameters from this online Wire Gauge Conversion Chart
#14 AWG is 0.0641 inches in diameter
D = 25.4 mm/inch * 0.0641 inch = 1.63 mm
My antenna is 2.8 inches wide for 24 turns. or 0.1167 inches/turn or 2.963 mm/turn.
R = width of 1 pitch/width of wire =(25.4 mm/in*2.8 in/24)/(1.63 mm) = 1.82
(I think this is how the RJELOOP3 parameter R is defined.)
I assumed here that the receiver is to be tuned to the 24 kHz Cutler, Maine transmitter.
L Length of one side of square frame, mm .... 1208 N Number of turns of wire on the frame ...... 24 D Diameter of wire, milli-metres ............ 1.6 R Ratio of (winding pitch)/(wire diameter) .. 1.82 F Frequency, kilo-hertz ..................... 24 Inductance ................. 1864.2 micro-henrys Inductive reactance ........ 281 ohms HF loss resistance of wire . 1.84 ohms Radiation loss resistance .. 0.00 milli-ohms Self-resonant frequency .... 1.1 mega-hertz, approximately Total capacitance required . 23590 pico-farads for resonance deduct stray capacitance 10 .. .. Setting of tuning capacitor. 23579 .. .. .. .. Approximate coil Q ......... 153 Receiving sensitivity ...... 91 decibels below 1/4-wave vertical Width of winding ........... 69.9 milli-metres Total length of wire ....... 115.97 metres Impedance seen across loop . 42.9 K-ohms, when tuned to resonance Impedance seen by Receiver . 0.1 K-ohms, via 1-turn coupling loop
Note that the calculation of 23590 pico-farads for resonance (same as 23.59 nfd or 0.02359 ufd) is very close to what my loop required for tuning.
Unless I have made some stupid math mistakes, this program should be very useful for building SID receivers. For instance, I have about 150 ft of #14 wire left from my 500 ft standard spool. Why not use all the wire and make an even more sensitive antenna? It would only be about 1 inch wider than the 24 turn design. RJELOOP3 makes it easy to compare different antenna shapes, sizes, frequencies, wire diameters, etc.
Two SID VLF system designs are in common use: 1) the Stokes design uses a tuned (narrowband) receiver and an untuned (wideband) antenna, and 2) the Hossfield design uses a tuned antenna and an untuned receiver.
You will need to get an accurate time reference to Universal Time (UTC) (Greenwich England time without daylight saving time) since you want to know the arrival time of SID-GRB within a second of UT. Some folks hook their electronics to GPS or WWV radio systems but I am too cheap for that. I looked for some way to make my PC clock accurate to within a fraction of a second per week instead of its usual several seconds per hour of error. Here is what I came up with:
I found when I started my seismometer project in 2000 that most of the existing seismic data logging software was programmed to accept data from a few PC a/d boards, and most of the programs did not accept the ASCII data records that microprocessors can easily output. However I found one program that the author was willing to modify to accept simple ASCII records: the freeware program Amaseis. Here is all of the seismic software that I am have heard of that might be of use for SID-GRB data logging. Please send me links to all the software I have missed.
I started on some Visual Basic software for data logging, but I have not had much time to work on it. Perhaps we need an open software project to develop SID-GRB software. Please if you have some interest in this type of project.
hits since April 3, 2010.
This page was created by , and last updated on October 25, 2011.