Hacker News Reader

> Unfortunately, many of these frequencies are used by our tech.

So what? Microwave frequencies aren't entirely line-of-sight, but they aren't going to diffuse very far off-target. Unless you have houses in between elements of the receiving antenna array, the disruption of comms in the immediate area isn't going to actually affect anybody. Perhaps there's some risk to jets that choose to fly through the energy beam.

View on HN

The transmitter would be located in geostationary orbit ~35,000 km away from the receiver, so spread due to diffraction becomes significant. With 6.7 GW of transmitted power at 2.45 GHz, ~790 MW ends up in the side lobes[0]. So it is reasonable expect RF interference not only near the receiver, but thousands of kilometers away from it. Figure 55 in [0] shows a plot of incident power with distance from the receiver. As this spread is due to diffraction, the only way to lessen it using the same frequency is to build the transmitter larger. In the case considered here, the transmit aperture was already 1 km.

[0]https://ieeexplore.ieee.org/document/9318744

Yeah, but that directionality is bumping up against the vastly different levels of power: you don't just need a little attentuation between your target and the wifi, you need something like 12 orders of magnitude attenuation. That's not so easy over long distances. See the paper OP cited which does actually do the math instead of handwaving.

Reply on news.ycombinator.com