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ARRL Propagation Bulletin ARLP027 (2019)
The American Radio Relay League (ARRL) is the national association for amateur radio, connecting hams around the U.S. with news, information and resources.
hamradio  propagation  Radio 
5 weeks ago by dcowhig
A New Wireless Communication Paradigm through Software-Controlled Metasurfaces - IEEE Journals & Magazine
Via Marina Petrova May 2019

Abstract:
Electromagnetic waves undergo multiple uncontrollable alterations as they propagate within a wireless environment. Free space path loss, signal absorption, as well as reflections, refractions, and diffractions caused by physical objects within the environment highly affect the performance of wireless communications. Currently, such effects are intractable to account for and are treated as probabilistic factors. This article proposes a radically different approach, enabling deterministic, programmable control over the behavior of wireless environments. The key enabler is the so-called HyperSurface tile, a novel class of planar meta-materials that can interact with impinging electromagnetic waves in a controlled manner. The HyperSurface tiles can effectively re-engineer electromagnetic waves, including steering toward any desired direction, full absorption, polarization manipulation, and more. Multiple tiles are employed to coat objects such as walls, furniture, and overall, any objects in indoor and outdoor environments. An external software service calculates and deploys the optimal interaction types per tile to best fit the needs of communicating devices. Evaluation via simulations highlights the potential of the new concept.
propagation  metamaterials  nanomaterials  wireless 
12 weeks ago by pierredv
mmWave 5G real-world deployments will require very dense networks: report | FierceWireless apr 2019
"Moore conducted his tests using the Motorola Z3 handset with the 5G Moto Mod adapter. Verizon gave him a list of nine cells, and he tested about six of them while walking around Chicago.

Moore said he received a top speed of 500 Mbps during his tests. “It’s very zippy under favorable conditions with line of sight,” he said, but added that mmWave doesn’t penetrate obstacles and it doesn’t travel far."

“Moore said he tested the signal speed through a pane of glass in a restaurant that was only about 25 yards away from a cell node. “I found that the speeds were roughly halved from what I was getting outside on the street,” he said. The initial real-world 5G network tests make clear the 5G networks that use mmWave spectrum will face a lot of challenges. “It requires a very, very dense network,” Moore said.”
FierceWireless  propagation  mmwave  5G 
april 2019 by pierredv
Arrow
Functional companion to Kotlin's Standard Library
arrowkt  monad  comprehension  docs  bindingCatch  error  propagation  multithreading  coroutine  async 
january 2019 by lgtout
Consequences of a living on a sphere
Because the World is not flat, you can’t see forever. As you look out to the horizon the planet falls away from you. This limits what you can see.
An adult person of around 6 ft tall has eyes approximately 1.8 m above the ground (yes, I'm using the Metric system). For the radius of the Earth, I'm going to use the value 6,371 Km (the mean radius). ... The solution is that the furthest an adult can see is 4.79 Km (which is just short of 3 miles).

The top observation deck of the Eiffel Tower is at 273 m.
From this altitude, the horizon will be 58.98 Km away (36.65 miles).

The top floor of the Burj Khalifa tower in Dubai is 621 m high.
This would give a viewer a theortical view over the desert of 88.96 Km (55.28 miles).

An airliner cruising at 38,000 ft is at an altitude of 11.58 Km
Plugging this into the formula reveals an answer of 384.3 Km, which is 238.8 miles.

When we were dealing with small altitudes, the difference between the straight line distance, and the ground distance along the curve of a planet was insignificant. Let's calculate the delta between these two distances for our cruising aircraft.
For a plane at high altitude, the difference between the straight line distance to the horizon and the curved distance on the Earth is about 500 m. (The difference when dealing with our first example of a man of height 1.8 m is a fraction of a millimeter).

The Golden Gate Bridge, possibly the most photographed bridge in the World, spans the opening of San Francisco Bay. Completed in 1937, it boasts two towers of height 230 m and these are 1,280 m apart. The top of the Golden Gate Bridge is almost two inches wider at the top than the base because of the curvature of the Earth!
distance  horizon  propagation  sphere  aircraft  airplane  altitude  geometry  trigonometry  Pythagoras 
december 2018 by Tonti
Global DNS Propagation Checker - What's My DNS?
Instantly check your domain names current IP address and DNS record information against multiple name servers located in different parts of the world.
network  tool  tools  DNS  propagation  check  domains  checker  web  jk-www  jk-analyst  jk-software  jk-webtools 
december 2018 by websitejk

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