Should I set WiFi channel to auto or manual?

Most devices will select the best channel on boot up only, and generally speaking they aren't good at it.

If you are using 2.4 GHz band, I recommend you to use channels 1, 6, 11 (wide bandwidth) to avoid interference, though they aren't the very best for all cases.

For the optimal results use this WiFi Analyzer app, it will tell you the best channel to use for both bands, even if nearby WiFis are not turned on all the time you can always open the app multiple times during the day, then write down the best channels, and select the common best one.

Why Japan is the only country that supports WiFi ch.14?

Japan is notoriously forward thinking when it comes to technology applications. They may have freed up this space from legacy technology or maybe never used it at all as much of what they do has their own standards for technology.

Where as the rest of the world and the US is very slow to discontinue old services. So many bands around the world are tied up by old technology that depended on the upper echelons of the 2.4ghz frequency.

The link above comments on global military use, we may never truly know the real reason many bands are reserved other than for "Military Use".

Trust me there are many many frequency ranges reserved for government use.

How can I tell if I need a new router?

Find out what internet speed you pay for from your Internet Service Provider.

Run a website based bandwidth speed test.

Make notes of the results.

Speedof. And others are good sites to test, avoid testing provided by your ISP - it is inaccurate for your purposes.

Run the test if possible from an Ethernet connected device (a network cable connected game console, desktop/laptop, or other devices connected by Ethernet that can provide a bandwidth benchmark). A score dramatically less (more than 50% less) than ISP stated bandwidth merits consistent testing and then a complaint to your ISP.

Next run the bandwidth test from wifi, standing right next to the wireless router (a smart phone works best for this stage of testing). A much slower speed at this stage indicates an aging or weak wifi router, power off and on the wifi router, if results are similarly poor compared to your Ethernet, try a different testing device and then contemplate replacement.

Now move as far away as you can while keeping your wifi testing equipment in line-of-sight of the wifi router. Run the bandwidth test again at this time. If results are still within 80% of original results at 35m then proceed. Otherwise, change testing devices and contemplate a new router if results are consistently poor.

Now go to an area of the structure that has one wall between the testing equipment and wifi router. Run test. If results are significantly lower you may need to switch testing devices or contemplate a router replacemect, or a mesh network to assist in penetrating heavy walls (or run all Ethernet).

Also check for signal obstructions like a microwave in between you and the router, as these can impede or interrupt the wifi connection.

Why do WiFi channels have overlapping widths?

Each channel in the 2.4 GHz frequency is usually 20 Mhz wide, which is the channel width. What it means is, a device cannot project a radio signal at EXACTLY 2.412 GHz (well theoretically it could, but then you can't squeeze much data in it with such a narrow spectrum).

So in practice, Channel 1 (2.412) actually occupies frequencies from 2.402 all the way to 2.422 - 20MHz Channel

The reason for the channel width is to host more data 'sub-carriers' meaning the 20Mhz width frequency is further divided into smaller partitions (52 sub-carriers), each sending its own data in parallel. This in turn maximizes data throughput. (Note that previous WiFi technologies used Frequency Hopping, so the channel width is the channel 'within' the hops could occur, google up FHSS if you're interested)

Imagine taking the whole visible light spectrum and dividing them into 7 colours of the rainbow, each colour transmitting a different stream of bits, each colour will he considered a subcarrier, and the entire visible light spectrum the entire channel width.

Best WiFi channel for 2.4 GHZ band?

As for the 2.4 GHz band the best channel to use is the one that is not overused by your neighbors, channels 1,6,11 have wider bandwidth so they suffer less from interference, though they are NOT the best ones to choose in all cases.

For the optimal results, I recommend you to use this WiFi Analyzer app.

This app will analyze your nearby WiFi networks and will till you the best channel for your case in order to avoid interference.

Should I use 40 or 80 MHz frequency for a 5 GHz WiFi?

Choose 80 MHz definitely, wider bandwidth equals less interference.

As for the channel, 5 GHz band doesn't usually suffer from interference, though for the best results try to choose a channel that is not overused by nearby networks, I really recommend you to use any WiFi analyzer app to do so, especially this WiFi Analyzer app, it’s free and helped me figure the best channel to use for my dual band router.

Is it really possible to hack WiFi using CMD?

Interesting question. Normally I would use Kali Linux for this task. Kali has built in tools that make WiFi cracking easier. But if you are forced to use a Windows OS for this task, I would use the application Wireshark. Wireshark is built for network reconnaissance. But, that is not what the question wanted. You want to know how to hack Wifi using cmd.exe

First of all, cmd is a little outdated. For this task, I would use Powershell. If you are working on Windows 7 or later OS, you should have Powershell pre-installed. While there are some wifi network using cmd. You my find using cmd is cumbersome.

Secondly, Microsoft has already written a document describing what you want to do. Read ‘Get Wireless Network SSID and Password with PowerShell’. This document should point you in the right direction.

Finally, know that what you are attempting to you is most likely illegal in your area. You want to be well versed in your country’s laws. In my area, passively monitoring a wifi network is usually legal, attempting to access that network is illegal. Do not send deauth attacks. Do not attempt to log onto a network that you do not have formal access to. Seriously, do not do it.

Have fun and be safe!

What is the difference between wifi router and wifi modem?

Router and Modem are two different technologies, but often come in one equipment. 

A MODEM is MOdulator DEModulator. Your Internet or network on TCP/IP protocols with Ethernet cabling & standards. If your ISP is using a different connectivity type e.g. Coaxial Cable (Internet and Cable TV together) or its on a telephone line (Internet + Phone) you will have to use a MODEM for converting your PC to Internet traffic digital signalling to ADSL etc... and back. 

Routers function is to connect different networks (Layer 3 of OSI Network Model) together. When you take a internet connection from ISP, you get only single IP. So to use multiple devices like phone etc, you can put a Wireless Router. Your devices will connect to the router and you can enjoy internet on all devices. If you have a modem based internet, then router uplink can be connected to this modem.

Is Wi-Fi harmful to the human body?

No. Wi-Fi and Bluetooth radiation is much too low energy to cause any damage. And by "too low energy", I mean the photons are low frequency so that the quanta of energy is too small to interact in any meaningful ways with any biomolecules. It's referred to as "non-ionizing radiation". In contrast, UV radiation (e.g. from the sun), is a form of "ionizing radiation" and can (and does) actually directly damage DNA, which is why too much tanning can lead to skin cancer. So, the sun is much more dangerous, because there is a lot more high-energy photons than Bluetooth.

Who is the inventor of WiFi?

First, let's take a look at the history of the 802.11 standards (radio frequency) used for broadcasting a WiFi signal. Secondly, we have to look at the electronic equipment involved in sending and receiving a WiFi signal. Not surprisingly, there are many patents connected with WiFi technology, though one important patent stands out.

Vic Hayes has been called the "father of Wi-Fi" because he chaired the IEEE committee that created the 802.11 standards in 1997. Before the public even heard of WiFi, Hayes established the standards that would make WiFi feasible. The 802.11 standard was established in 1997. Subsequently, improvements to the network bandwidth were added to the 802.11 standards. These include 802.11a, 802.11b, 802.11g, 802.11n and more. That's what the appended letters represent. As a consumer, the most important thing you should know is that the latest version is the best version in terms of performance and is the version you would want all your new equipment to be compatible with.

Who Owns the WLAN Patent?

One key patent for WiFi technology that has won patent litigation lawsuits and does deserve recognition belongs to the Commonwealth Scientific and Industrial Research Organisation (CSIRO) of Australia.

CSIRO invented a chip that greatly improved the signal quality of WiFi.

According to the tech news site PHYSORG, "The invention came out of CSIRO's pioneering work (during the 1990s) in radio astronomy, with a team of its scientists (led by Dr. John O'Sullivan) cracking the problem of radio waves bouncing off surfaces indoors, causing an echo that distorts the signal. They overcame it by building a fast chip that could transmit a signal while reducing the echo, beating many of the major communications companies around the world that were trying to solve the same issue."

CSIRO credits the following inventors for creating this technology: Dr. John O’Sullivan, Dr. Terry Percival, Mr. Diet Ostry, Mr. Graham Daniels and Mr. John Deane.

Could my neighbor be jamming my Wi-Fi?

Yes, in fact i once did it by mistake.

I supplied higher voltage to an ESP8266 chip than the rated one by mistake, and it jammed most of the nearby WiFi networks.

Your neighbor might be doing it by mistake, maybe you both have a strong WiFi signal on the same channel.

Any WiFi scanner app will help you detect that, this WiFi Analyzer app will even tell the distance between you and the neighbor’s WiFi network, If signal quality of your neighbor’s WiFi network is larger than (-20 dBm) he is most definitely using a WiFi jammer.

Why does a Wi-Fi router slow down over time?

Many things can cause your WiFi router to slow down overtime, the challenge is to find the true reason that is causing this slow down.

Below are the main three reasons that can cause you WiFi router connection to slow down:

1. Router Placement

Most people underestimate the importance of picking a good spot for a WiFi router, Make sure you’ve placed your router in the right position, away from any electric devices, away from metal objects and concrete.

2. Interference

Make sure your router is away from radio emitting devices, like microwaves, surveillance cameras, and so on.

Also your neighbor’s WiFi routers might be interfering with yours, try to choose a channel that is not overused by nearby networks, I really recommend you to use any WiFi analyzer app to do so, especially this WiFi Analyzer app, it’s free and helped me figure the best channel to use for my router.

3. Bad Quality Router

Some router manufactures produce low quality units that have short lifetime.

When you buy a router make sure it has long warranty, good thermal design, and finally from a good reputable vendor.