There are many interesting phenomenas on the area of free - energy devices and with the devices that produces antigravity effects.
After researcing this kind of systems, i found that there is one common thing that exsists behind with almost every this kind of devices,for exsample bifilar coil type devices( Mark device etc. ),Grays device, Testatika Machine,Searl generator, only to mention of few.
This common thing is ability to produce source free magnetic structures ( SFMS ).This kind of magnetic structures, SFMS ,differs of conventional magnetic fields,because they are not closed systems, but open systems,it is one kind of dipolar magnetic, long and straight line.
The needed technology to produce this kind of magnetic structures is based on to method, how to cut the magnetic energy from the EM- half wave.
This can be possible,if we cancel the magnetic field by sharp DC-pulses, for exsample with a Caduceus coil structure,that is one kind of bifilar coil.
This piece of the wave is a open system,that has a property to pump energy from the distance, but only in to one direction,the system is like request to have energy,and we can have energy back as an answer.This process happens by phase conjugation, when reguesting singnal and answer signal are are with excactly same line and phase.
Another property is that SFMS can go through all the matter, without a much attenuation or reflection.
Detection of SFMS with a conventional EM-instruments is not easy,because most of the instruments are designed to detect EM-waves.Anyway, there are created instruments also to detect SFMS lines.
If you are interested about the subject,there is available some theoretical files,by Bibhas R.DE
http://www.journaloftheoretics.com/Links/Papers/BibhasDe.pdf#search=%22magnetostatic%20wave%20source%22
Regards,
Esa