All Questions
24 questions
0
votes
1
answer
116
views
Communicating 1/4 miles without Wi-Fi. (I want to design a driveway alarm.) [closed]
We live in a very rural area of Ohio. Our driveway is 0.25 miles (400 m) long. I would like to design an alarm that will alert us when someone turns into our driveway.
The easy part is the optical ...
- 101
8
votes
4
answers
4k
views
Do cell-phone base station antennas emit the same power as cell phones?
Do cell-phone base station antennas emit the same power of waves as from a cell phone?
I would assume so because both waves need to travel the same distance, right?
- 925
-1
votes
1
answer
261
views
How or why are powerful but low-frequency radio waves, such as from a radio station or cell tower, potentially dangerous? [closed]
Cell towers / base stations and such are limited in the power they are allowed use, even if the wavelengths of radiation used do not adversely affect people or animals.
I have heard (and read) that it ...
- 233
1
vote
0
answers
96
views
Height or antenna gain for a ship mast cell antenna
I'm optimizing my ship's WAN using cellular modems and looking to improve distance connectivity over speed in an either or option challenge.
Our ship's mast has two cell antennas which are currently ...
- 11
0
votes
1
answer
193
views
What components would I need to receive SMS-CB messages? [closed]
I could simply use a LTE modem for this (with a SIM Card). But since SMS-CB is an FTA (Free-To-Air) signal, having to buy a SIM card for this (I know, it's not expensive) would be overkill.
I am ...
- 103
2
votes
3
answers
3k
views
Pinging a dead cellphone
Can a dead phone still be pinged? I was watching a news clip recently of someone lost in the woods with a dead phone that still managed to be pinged. How it this possible? I'd imagine it's some sort ...
- 21
4
votes
2
answers
874
views
What kind of oscillator circuit technology is used for 5G technology?
In particular, are 5G oscillators found in cellphones using some kind of SMT/fabricated Gunn diode or Impatt diode(on a chip)? The frequency bands(K band) are beyond the range of crystal oscillators. ...
- 734
0
votes
2
answers
215
views
4G LTE: Is it possible to make a high gain antenna that resonates well for two frequencies, where one isn't a close harmonic of the other?
I want a high gain antenna for Verizon LTE data to my JetPack 7730L but don't really see one as high as say this MIMO parabolic antenna that's probably design for 2.4 GHz WiFi. From all I know it's ...
- 105
0
votes
3
answers
751
views
Can I use a 2.4 GHz rated parabolic MIMO antenna for 700 MHz Verizon 4G LTE data?
Can I use a 2.4 GHz rated parabolic MIMO antenna for 700 MHz Verizon 4G LTE data?
It seems 700 MHz are a long ways from the range of a 2.4 GHz antenna, but I have seen people marketing similar ...
- 105
0
votes
2
answers
131
views
How does two way communication between a baseband modem (on a phone) and a mobile phone mast work?
I've been thinking absent-mindedly about how mobile phone communication works when I wondered how something as power efficient as a mobile phone can have such a powerful radio. I am guessing that most ...
- 155
0
votes
2
answers
105
views
Is there any physical limitation to cell carries sharing the same frequency?
Currently in the U.S. certain companies are granted leases on certain frequencies for cell phone communication. I was discussing with a friend how this allows a company with a lower frequency to get a ...
- 101
3
votes
1
answer
224
views
Why can't we divide the electromagnetic spectrum into arbitrarily many radio frequency bands?
I understand there is concern over the limited amount of wireless spectrum available for allocation but am somewhat confused as to why. Couldn't we just divide the electromagnetic spectrum into as ...
- 141
1
vote
1
answer
224
views
How can a phone transmit the signal back to tower? [closed]
If cellphones have such a low power transmitter (around 200mW for LTE) and also doesn't have directionality then how can they talk back to the tower even though they are so powerful and built ...
0
votes
3
answers
121
views
Velocity limit of UMTS and (or) CDMA2000
If the client is moving relative to the base station, the Doppler shift would compress or extend the packet. If the effect is strong enough, the PN generator in the receiver will eventually get out of ...
- 141
14
votes
2
answers
9k
views
Why do only high-end phones support a lot of LTE bands?
Most lower and middle end phone only support 3/4 LTE bands. High end phones, like the iPhone, or flagships from Samsung and LG also support a lot of bands.
iPhone 7: 1, 2, 3, 4, 5, 7, 8, 12, 13, 17, ...
- 259
0
votes
1
answer
129
views
Best way to estimate number of 'active' cell phones nearby
I work in a place where we're very interested in ways to measure occupancy, one way being to extrapolate this data from an estimate of the number of cell phones near to a fixed point.
How does one ...
- 103
1
vote
3
answers
2k
views
Is there a metal that will not interfere with smartphone reception as a case?
I want to design an iPhone case that will include a metal plate on the back of it. Is there any kind of metal that will not interfere with the phone's reception?
- 159
0
votes
2
answers
649
views
EMF transmission from cell phone's battery
According to Cell Phones & Wi-Fi―Are Children, Fetuses and Fertility at Risk?
While one can put the phone in ‘airplane mode,’ which disconnects it from Wi-Fi and the Internet, the cell phone ...
- 105
3
votes
2
answers
2k
views
Headphone cable as antenna
How can headphone cables act as Antennas for built-in radios in smartphones ? Is it possible because of different frequency channels or what is the theory/mathematics behind this?
On a side note, ...
- 185
0
votes
2
answers
142
views
Is it possible to detect cellphone IDs in an enclosed area
I'm working on a project where I need to be able to identify different cellphones in an area.
Ideally I need a way to identify when specific cellphones enter and exit a range - this could be IMEI or ...
- 109
0
votes
1
answer
128
views
RF: what are some sources that are transmitting few hundred of watts signal power?
I am looking for some source (TV broadcasting station, or cellular tower,etc) that transmit a few hundred watts of power. (Just typically please).
Please give me some idea to get me started so I can ...
- 205
4
votes
1
answer
2k
views
how does a cell phone transmitter work?
I came across a question that is really puzzeling me. I did some basic calculation for a cell phone transmitter. I based on 900Mhz band and assumed a 20Km distance to a cell tower. On top of that I ...
- 305
18
votes
2
answers
20k
views
Why do my speakers make a noise when my cell phone gets a call? [duplicate]
It's a very common sound but I've never thought to question why it happens.
- 343
3
votes
2
answers
323
views
Any idea on any device which track multiple mobile phones
I'm currently ask to work on a project which I have never worked before.
And I have no freaking idea or its not even in my area of expertice.
Ususally I Google as everyone does. But what is the use ...
- 131