# Tag Info

35

Yes, WiFi and Bluetooth can disturb each other. But both are equipped to handle that. A standard that is not capable to handle disturbance and/or interference will simply be unusable under many circumstances. The 2.5 GHz ISM band is also used by Microwave ovens and other wireless standards like Zigbee. Wifi transceivers are able to detect when certain ...

16

Wifi uses a listen before transmit system. If the channel is busy, it holds off transmitting. Eventually it gets through. Each channel is fixed. If it tries to use a channel that is busy, from bluetooth, then it will wait. This may reduce the data speed for wifi if it has to wait too much. Bluetooth for over a decade now uses adaptive frequency hopping (...

11

The question is not exactly about the wifi, but on how does this operate in full duplex It doesn't; read the more detailed specification on the page you linked: - Operation Mode: Bi-directional, half-duplex, Auto-Switching via carrier sensing. The full detailed spec is here: - Operation Range: 2400-2500 MHz.Operation Mode: Bi-directional, half-...

9

What will be the simplest circuit that outputs 1 when it receives a predefined or pre-programmed WiFi packet? Something that "speaks" Wifi enough to detect packets on the air, synchronize to them, extract the bits from them, apply forward error correction (the likelihood of you ever receiving a full WiFi data frame without a single bit error goes strongly ...

9

Your calculations check out for the given values, but keep in mind that the dielectric constant of FR-4 is not tightly controlled, and may vary between 4.35 and 4.7 between manufacturers [1]. Since your trace length is very short, this variation will not have a big effect (you can try the values in the calculator). For more demanding applications, special ...

6

for this short of a distance (under 1/8th of a wavelength) impedance requirements get a lot looser, so on that premise its more than suitable, and lines up with my own calculator. As to the layout, I cannot particularly fault it, you're keeping good separation between it and other nearby signals, you have vias right next to the signal ground so the return ...

5

A lot of people worry about health effects of electromagnetic radiation, and you'll find a lot of scaremongering misinformation on the web, but it is generally agreed by doctors and scientists that the electromagnetic radiation from WiFi equipment is extremely unlikely to cause any remotely significant risk of cancers. The World Health Organization says: ...

5

Is it a misconception that higher frequency channels support a higher bit rate or is it true for some reason? It is not the (carrier) frequency itself that determines the supported bit rates but the available Bandwidth of the channel Suppose I have 10 MHz of bandwith available at 100 MHz, for example 100 MHz to 110 MHz or I have 10 MHz of bandwith ...

4

tl; dr: ZigBee isn’t a subset of WiFi (802.11). It is a different protocol family, just as Bluetooth is another different protocol family. ZigBee, BT and WiFi are not directly compatible with each other, but will co-exist in the same band. What Is ZigBee, And How Is It Different From 802.11, Really? ZigBee (802.15.4) is a family of protocols used for low- ...

4

To what others have said, I'll add, You probably don't want to let the ground fill in between the pads of your DC-blocking capacitor. This will probably lead to excess capacitance to ground, and degrade the return loss of your RF input. You may want to move the RF connector a bit further away, so that the blocking capacitor doesn't have to be directly ...

3

Sure, just attenuate it (50-60dB). You don't want to saturate the receiver. As for collisions, they happen on air too (at different power levels). If you have a MIMO NIC with multiple SMAs, you can even play with the phase a bit.

3

They are completely different set of modulation and MAC layer protocols. From an RF point of view, WIFI has 20, 40, 80 and 160MHz channels (depending on the specific band and flavour), with DSSS or OFDM (depending on the flavour). ZigBee uses 5MHz channels.

3

Decibel, or dB, is a measure for a relation of two parameters. $Decibel = 10 \cdot log\frac{P}{P_0}$, with $P_0$ beeing the parameter you compare your signal with. For calculating the gain of an antenna, you compare the recievable power at some point with the recievable power at that same point when a simple dipole antenna is used. When the power in ...

2

This should be enough for the purpose, the power reduction will only reduce the distance but depends on how complex you want your circuit to be. To compensate this you would need amplifiers both for transmitter (PA) and receiver (LNA) chains.

2

Bottom line is that it probably won't work very well if you need very high gain. First things first. Satellite dishes usually have a receiver in them. You can't use the receiver. It is tuned for a different band. In theory, you could replace the receiver with a wifi transceiver, and then, if you aim the dish correctly, it could work. But there is another ...

2

It is both. Basically it is legal issue, because it can be a technical issue. Like you guessed, an untested antenna can cause undesired radiation. FCC is a bit strict on this matter and you can't just do the required tests that prove it works and send them the report. Unless you forget about the pre cert and do all the radio tests yourself. You have to make ...

2

If you modify a pre-certified module, it then become (in my mind) a non-certified module, and you get to re-test it. That may or may not fit into your budget. Under FCC rules you cannot modify the pre-certified module. A different antenna changes the gain and radiation patterns, which could also make it non-compliant to FCC standards. The FCC is kind ...

2

If you want the antenna to transmit through the sheet, the metal will need to be removed. For almost all metals, the skin dept at 2.4GHz is less than 0.1mm, and even lower for 5GHz. The skin depth is the amount of metal it would take to attenuate the signal roughly 1/3rd. If you want to transmit through the metal, it will need a metal free zone. It might ...

2

Because of the feedback issues that you mentioned in your question, neither in-line amplifiers, nor the transceivers "feeding" them, can operate in a full duplex fashion when transmitting and receiving on the same RF channel. In the transceiver itself, there are duplex switches that switch between the outgoing and incoming amplifier chains that are ...

2

To answer your specific question, 'is there a better alternative for mass production', of course there is. That alternative is the same for any module, nothing I am about to say is specific to the ESP8266. The better alternative to using the ESP8266 module in the context of mass production is using the ESP8266 chip. The modules have the advantage of ...

2

More to the point, is my microwave dangerous to people in the house? It could be, although significant power needs to be leaking for it to be dangerous: https://en.wikipedia.org/wiki/Microwave_burn Assuming the (900 Watt Panasonic brand) microwave is to blame for the original WiFi performance issue, could it also be possible that the leaked RF energy has ...

2

I think you should make a difference between 'scanning' the buttons and sending them. Scanning I would do very fast, as you say, you cannot press them faster than 10 ms, but maybe others can so maybe you need even a faster scan. For sending (wirelessly), you can send them only when changed (as long as you know the receiver received it with some return ...

1

Do what every other controller does, and just send all the buttons in every data package. You only need one bit for each button (rounded up to a whole number of bytes). This makes it much simpler, because there is no need to make sure that the game has received a change and resend any changes that it didn't receive. Yes, it will save bandwidth if you only ...

1

Generally, if your metal enclosure is grounded and thick enough, congratulations, you might have built a faraday cage and no RF enters or leaves. In reality, the thing is probably not a perfect Faraday cage, and you're just greatly reducing the performance of your Wifi by abusing the enclosure as a very bad antenna element. So, yes, a plastic window would ...

1

There are many Wifi modules available with an SDIO interface, which enables speeds of several hundred Mbps (so you will probably be limited only by your Wifi link) and is much more straightforward to implement in an FPGA than USB or PCI-E.

1

According to https://docs.espressif.com/projects/esp-idf/en/latest/api-reference/peripherals/spi_master.html: The ESP32 has four SPI peripheral devices, called SPI0, SPI1, HSPI and VSPI. SPI0 is entirely dedicated to the flash cache the ESP32 uses to map the SPI flash device it is connected to into memory. SPI1 is connected to the same hardware lines as ...

1

Hate to say it, but I've been here and done this... if you want to knock out the router I'd just buy a shielded tent. If you get a shielded tent, like this: https://www.tequipment.net/TekBox/TBST86/49/45/1/EMI-Accessories/?v=0, it'll attenuate the 2.4GHz frequencies. (I own a larger one, and it does work quite well at 2.4GHz). In my experience, the only ...

1

Is this a common experience? Can anyone explain how this is possible? Faraday cage says what? Copper has a skin depth of 1.3um at 2.4GHz, so it doesn't take much copper to attenuate a wifi signal. To properly build a faraday cage, you cant have apertures (holes), which you have some where the cables come out, or conductors crossing the boundary. The ...

1

Before you assume your router is damaged, you should first shut it off and restart it. It probably maintains a list of wifi channels where it has seen a lot of intereference, and avoids those channels. Over time, it may have simply "black listed" all the available channels because of too much intereference. A shutdown and restart should clear the list. A ...

1

This is not exactly an electronics question, rather a networks one. To put it simply, when connected to a router (here, your phone), a device has a private - or local - address, which you use when connecting with devices also using your phone's hotspot, or network. They are usually between 192.168.0.0 and 192.168.255.255 or 10.0.0.0 and 10.255.255.255. The ...

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