You're welcome to try, but bear in mind anything that you radiate at those frequencies, particularly 10 MHz., will propagate for thousands of miles, and will likely get you a visit from the feds for interfering with a licensed radio service called WWV.If you build a long range wireless energy transfer device, why can't you use a lower frequency than the microwave range to transfer energy? Why does it have to be microwaves? Why not say 10 megahertz?
Yes. The wavelength in meters is 300 / frequency in MHz. So:
Look at the original WiTricity hype from smart people who must have known better. Look at the size of a single near-field 9.9 MHz RF resonator designed to minimize far-field RF radiation.
https://en.wikipedia.org/wiki/WiTricityIt was not to be, and Intel abandoned its Rezence-based attempts in 2016, and by 2017, Rezence was over in effect, drones never took off, and wireless homes were clearly well out of reach. WiTricity announced layoffs as a result, and now focuses solely on wireless charging systems for electric vehicles (EVs).
The term WiTricity was used for a project that took place at MIT, led by Marin Soljačić in 2006. The MIT researchers successfully demonstrated the ability to power a 60 watt light bulb wirelessly, using two 5-turn copper coils of 60 cm (24 in) diameter, that were 2 m (7 ft) away, at roughly 45% efficiency. The coils were designed to resonate together at 9.9 MHz (wavelength ≈ 30 m) and were oriented along the same axis. One was connected inductively to a power source, and the other one to a bulb. The setup powered the bulb on, even when the direct line of sight was blocked using a wooden panel. Researchers were able to power a 60 watt light bulb at roughly 90% efficiency at a distance of 3 feet. The research project was spun off into a private company, also called WiTricity.
NO. A single conductor fed from one end will have no directional properties to speak of. In order to change the radiation pattern in a useful way you need multiple elements of precise length and spacing. Research Yagi-Uda antennas. They are named after their inventors: Hidetsugu Yagi, and Shintaro Uda in the mid 1920's. these guys were pretty sharp.Hypothetically if I built an antenna 0.75 meter long, could I focus the radio waves into a beam? If I had a helicopter hovering 1 kilometer away and hovering 1 kilometer above the ground, could the beam deliver enough energy to power the helicopter?
That's a start, but there is very little useful design information there. There is a freeware program called EZNEC that can help you with design and simulation of various arrangements and spacing of elements. the lower limit on frequency is the 40 Meter band @ 7.0 to 7.3 Mhz. AFAIK there is no upper limit. I've seen a 35 element job for 1296 MHz. and I've seen a yagi made from paper clips for 3 GHz. Above those frequencies you are probably better off with a dish.Actually I have read the wikipedia article on yagi antenna.
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