Consider also the rf tag.
Questions tagged [radio]
939 questions
82
votes
11 answers
What's the cheapest way to link a few microcontrollers wirelessly at low speeds over short distances
What's the cheapest way to link a few microcontrollers wirelessly at low speeds over short distances.
I'm looking to keep it ultra-cheap, use common discrete parts and keep it physically small. I don't care about bands and licensing so long as it…
Toby Jaffey
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53
votes
11 answers
Can a radio transmitter somehow detect the number of receivers in its area?
During conversation, a colleague proposed that over-the-air television and radio broadcasters can determine the number of viewers or listeners based on the "load" on their signal. This seems to me like total bupkis, but he's piqued my curiosity and…
ghaberek
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41
votes
3 answers
Why do IR remotes influence AM radios?
When I put my IR remote near any AM radio and push any button on the remote, I can hear a sound from the radio speaker (like beeping). This phenomenon is very weird for me because the radio has no IR receiver inside.
On the other hand, the frequency…
M.A.K
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37
votes
9 answers
What is the basic difference between AM and FM radio?
I want to know the basic/fundamental difference between AM and FM radio. Why nowadays FM radio has replaced AM and has become more popular?
user11832
36
votes
4 answers
Why do characteristic impedances matter only when traces are longer than half a wavelength?
Why are characteristic impedances of traces not considered when the traces are shorter than half a wavelength? I've had the same issue with light diffraction, which happens when pinholes are smaller than half a wavelength - it sort of makes sense…
user42875
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34
votes
2 answers
How did 455 kHz end up being a commonly used IF (intermediate frequency)?
Of all possible IF frequencies, why did so many consumer radio and amateur HF radio manufacturers (and filter component vendors, etc.) end up converging on 455 kHz as the IF frequency, from the vacuum tube era, and onward? Is there something…
hotpaw2
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33
votes
3 answers
Why don't interfering radio stations both play at the same time?
Since radio-waves are additive, I would expect that overlapping stations (eg. two different signals broadcasting on 95.7 within range) to both play over my radio at the same time.
But that's not what happens. Instead, I hear only one station at a…
BlueRaja - Danny Pflughoeft
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32
votes
8 answers
Why don't we use lenses for RF?
Radio waves are a class of electromagnetic waves.
Light also is a class of electromagnetic waves.
By shaping a material in which the speed of light changes, we can bend the propagation direction of light, we call this a lens, and we call the speed…
valerio_new
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31
votes
5 answers
Stealing energy from radio towers or power lines
From this answer: How much energy can be harvested from nearby radio towers or power lines? What circuits would you use? How much would you have to absorb for it to be noticeable by the producers or by other consumers?
I see a lot of stories,…
endolith
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26
votes
5 answers
What does dBm mean?
When working with radios, I've seen the term "dBm". What does this mean?
The wikipedia page gives a table showing the equivalent power in Watts. Is the dBm output just the power level of a transmitter?
How does this differ from signal strength…
Toby Jaffey
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26
votes
4 answers
Why does radio reception consume so much energy?
On low-power radios, the current consumption for reception is similar to the consumption for transmission. For example, the Texas Instruments CC2652 System-on-Chip datasheet claims these values:
Active-Mode RX: 6.9 mA
Active-Mode TX 0 dBm: 7.3…
kfx
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23
votes
3 answers
What went wrong with my DIY project?
I have been teaching my son the basics of electronics by taking apart his old toys. We got to the level where we can fix things and put them back together. Last weekend we spent several hours putting the circuitboard of RC car #1 into RC car #2,…
Wapiti
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23
votes
14 answers
Do we know what a radio wave looks like?
In precalculus class, we are learning about sin/cos/tan/cot/sec/csc and their amplitude, periods and phases shifts. I've studied electronics on and off for about a year. I would like to know if we actually know what waves look like. Do they actually…
Foo Fighter
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22
votes
3 answers
Microcontroller with both ethernet and radio onboard?
Does anyone know of any (reasonably low-cost) SoC which combines all of:
Microcontroller (any architecture, at least 4KB RAM/8KB flash)
Radio transceiver (433MHz - 915MHz or 2.4GHz)
Ethernet MAC + PHY
(For a wireless sensor application -…
Toby Jaffey
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22
votes
3 answers
Dual-SIM phone, do they use 2 GSM modules ? Anyone has high level schematic?
As an slight extension of my project, I am trying to see if I can improve connectivity resilence by using a dual-SIM approach. Dual-SIM phones (or Tri-SIM, quad-SIM phones) are quite popular in many developing countries, and AFAIK, most are based on…
bdutta74
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