Where can people find additional information on EMFs? What are electric and magnetic fields? Electric and magnetic fields are invisible areas of energy also called radiation that are produced by electricity, which is the movement of electrons, or current, through a wire. An electric field is produced by voltage, which is the pressure used to push the electrons through the wire, much like water being pushed through a pipe.
A 20m loop — trying to squeeze every last drop of efficiency out of a loop on 20m A 6m loop — because, well, why not? A 40m loop — a truly small loop with capacitor selection cost-optimized for 40m A 10m loop — optimized for 10m, but also extendable down to 20m An 80m loop — that turned out to work really well on 40m, too The Mark-7 Magnetic field and choices an optimized 20m loop, with some alternative construction techniques The Zebra — another 80m antenna using a thin helix of copper foil Multiband Operation — How I match my loops for use on more than one band Next Steps — Some wish-list items for more research and permanent installations Conclusions — What I would do if I were to do it all over again Closing Thoughts — A discussion on why loop antennas aren't as simple as a few formulas Step 1 — Just the Essentials Starting out, I wanted to avoid investing any significant amount of money in an experimental antenna until I was convinced that the principles were sound, and that I could make them work for me.
People who use small loops often make impressive claims about their performance, but then again, even a light bulb can work the occasional DX station, right?
I wanted to prove the concept before committing a lot of resources to the project. Finding a quality tuning capacitor is the most difficult step in procuring materials, so I started with that. I had quite a bit of success using open-wire feed line for feeding and matching a dipole for QRO operation, and I knew that the voltage handling capacity of such line is quite high.
I decided on a basic and minimal small loop, 3' in diameter, using a stub made from quality window line as the tuning capacitor. Such an antenna would, in theory, readily resonate in the 20m band. This design would also allow me to simply discard the antenna if it didn't work well, without losing a lot of money.
This first loop was tuned for a single frequency, 14,kHz. I thought digital modes would be a good way to test the antenna, especially since so much digital activity is clustered tightly around a single PSK frequency on each band.
That would allow me to find the highest number of stations in close proximity to each other. In keeping with my cost-saving approach to my experimental antenna, the first mast was made from PVC plumbing pipe.
It is non-conductive, and the large-bore PVC pipe is very rigid at short lengths. I keep a surveyor's tripod handy for doing antenna experiments, so between that and the PVC, I had the materials to build the support.
This allowed a 10' overall height, that could be easily assembled and disassembled. Some things I learned about using PVC as a mast: If you cement the two together, one inside the other, the strength and rigidity of the mast increases substantially.
Most of the loops shown here use this arrangement in at least some part of the support structure. When using the threaded connectors, it is very wise to apply a small amount or not-so-small amount of dielectric silicone grease to the threads before trying to mate them.
Remember, this is plumbing pipe, and the various connectors are not meant to be disassembled repeatedly. They are meant to glue together and stay glued for decades.
The threaded connectors I used had a slight taper, which means they were also meant to thread together tightly, and stay that way.
Without some kind of lubricant to prevent this, I would eventually need some large wrenches to twist them back apart. Using a high-quality cement to join the pipe to the connectors is a must. Few things will ruin your day faster than watching your beautiful antenna creation come crashing to the ground because a joint worked loose.
Rebuilding an antenna is not. The tripod is a great way to support the antenna, but loop antennas can get very top-heavy. The tripod will easily support the bottom mast by itself.
Before threading the loop itself onto the bottom mast section, I made sure to guy the bottom mast section just above the tripod. This is absolutely mandatory. More than once, I had to catch a falling loop because the wind had caught it just right, and caused it to tip over.
The tripod wasn't enough to resist the leaning tendencies of the loops under wind load, even though the entire thing was only 10' above ground. The green guy lines in the pictures are relatively thick nylon rope. Nylon is not typically UV-resistant, so using it as a long-term guy line for a permanent installation is probably not a good idea.
There are inexpensive ropes available that are meant to be used as guy lines for permanent antenna installations, and these ropes are UV-resistant.
If you use nylon outside for long periods of time, the sun will eventually make it brittle to the point of failure.The idea of getting a machine or device like a magnetic pulser to naturally amp up your body's ability to heal itself is an exciting concept.
The amazing claims and benefits of magnetic pulsers or also called PEMF or Pulsed Magnetic Therapy run the gamut of stories from recovery from life threatening diseases to pain relief, better sleep and .
May 25, · If any human ever got close to a magnetar, they would quickly find themselves in dire straits. “Strong magnetic fields can start to do surprising things,” says Sutter.
Alnico Cow Magnets. This standard Alnico cow magnet has a magnetic pole on each end, and is perfect for a 3D demonstration of magnetic fields, .
Magnetic Screen Door 36 x 96, Mosquito Patio Screens Door Mesh 36 X 96 Fit Doors Size Up to 34”W X 95”H Max with Full Frame Hook&Loop French Back Door Curtain Keep Fly Bug Out. PSI Physics - Magnetism Multiple Choice Questions 1.
A bar magnet is divided in two pieces. Which of the following There is a magnetic repulsive force between the broken pieces. D. There is a magnetic attractive force between the broken pieces.
of a uniform magnetic field . The idea of getting a machine or device like a magnetic pulser to naturally amp up your body's ability to heal itself is an exciting concept. The amazing claims and benefits of magnetic pulsers or also called PEMF or Pulsed Magnetic Therapy run the gamut of stories from recovery from life threatening diseases to pain relief, better sleep and simply feeling more energy.