Radar, Very low Frequency, and Microwaves - are they useful for MARIACHI?
From MariachiWiki
To Be Considered
1. What man made sources of low-frequency waves exist?
2. What types of devices exist that detect low-frequency waves and how?
3. The range of low-frequency waves.
4. Affect on life.
5. Natural Sources.
6. Relation to cosmic rays.
7. What obstructs the path of the rays.
Definitions
Microwaves- These are electromagnetic waves with wavelengths longer than those of terahertz (THz) frequencies, but relatively short for radio waves.
Very Low Frequency- This refers to radio frequencies ranging from 3 to 30 kHz. There is little bandwidth in this band of radio spectrum. Therefore, only the simplest signals are used. An example of this is radionavigation.
Lightning strikes and pulsars emit very low frequency EM waves. Television systems (in most countries) relay the video using AM or amplitude-modulation and FM or frequency-modulation. Unwanted sources of these waves may interfere with MARIACHI. However, sources, such as lightning, may help in this project.
1. What man made sources of low-frequency waves exist? Radios and television sets recieve man-made low-frequency waves. Thse may obstruct the MARIACHI project and present us with a difficult challenge.
2. What types of devices exist that detect low-frequency waves and how?
One of the cheapest types is the Octoloop. The octoloop is a length of 25 pair telephone wire inside an octagonal loop shield of 3/4 hard copper pipe. It is about 7 ft dia and wired for 50 turns, and gimballed for noise rejection. The pipe shield is a very effective electrostatic shield at MF, and also reduces VLF/ULF microphonics, which for obvious reasons plague most loops. The self resonant freq has not yet been measured, but is probably near 12 kHz.
The octoloop is easy to make for about $20. You need some 3/4 in hard copper pipe, eight 45 deg elbows, and two male threaded adapters. You also need a 3/4 inch sealed conduit body tee, a 3/4 CPVC coupling, enough 25 pair cable to go around the loop, and your favorite connector.
Cut eight pieces of pipe to length "L" to make your loop the desired size. The finished diameter will be 2.41*L and the circumference will be 8*L. I used 36" for L, giving a finished size which barely passes thru a basement door. Now cut two pieces in half. Sweat two of the L/2 pieces into the male adapters, thread them tightly into the conduit body, and trim off both ends to reduce the total length back down to L.
At this point you should have eight pieces of length L, with one cut in half, and one with the conduit body inserted into it. Sweat the ends of the pieces and the elbows with solder. Lay out the octagon on a flat surface with the L/2 pieces opposite the conduit tee. Sweat together. Allow to cool, then clean.
Now to pull the cable through. Tie a thread to a small cloth rat and blow it through one half of the loop using a shop vac or hair dryer. Next, pull a strong cord through. Use wire pulling lube or liquid soap to help pull the wire through one half of the loop, starting in the conduit body. Doing each half separately makes a hard pull easier. Clamp the work in a vise or conscript a friend or family member if necessary.
IMPORTANT NOTE: slip the 3/4 inch CPVC coupling over the wire before pulling into the second half! Continue in the same manner to complete the loop. When the wire pulls tight, it should pull the two L/2 pieces snugly into the CPVC coupling. This insulator is important to prevent the shield from becoming a shorted turn.
If you used 25 pair cable, you have 50 turns to splice together. Use solder and shrink tubing to splice together ten 5 turn windings which can be put in parallel for 5 turns or in series for 50 turns. Splicing took less than two hours. Mount your favorite balanced connector in the third port of the conduit tee, or use a bushing to pass a balanced cable. Use XLR microphone connectors and mic cable for balanced loops. A small preamp may be put inside the conduit body. Octoloop is mounted via cable clamps on a 2x4 with a gimbal in the center.
3. The range of low-frequency waves.
The range is 30–300 kHz.
4. Affect on life.
Further epidemiological studies and research into biological effects of em radiation and magnetic field (including chemical reaction in the body) is needed to fully understand and determine all health effects resulting from exposure cases. Cases involving exposure to em radiation should be considered on a case by case basis taking into consideration the circumstances surrounding it. It is premature to enforce specific guidelines for exposure to ELF radiation. However, a program which addresses ELF hazards identification and training is encouraged.
5. Natural Sources.
- Pulsars
- Lightning
- Aurora
- Earth's magnetic field
6. Relation to cosmic rays.
7. What obstructs the path of the rays. Ionized atmosphere (possibly caused by meteors and cosmic ray showers.)
The previous information was obtained through various sources on the web.
