Consider also the rf tag.

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-1
votes
3answers
284 views

Is it possible to exchange information between arduino and android phones easily using nrf24l01? [duplicate]

I need to send information from arduino to an android phone, having some app actively listening for radio communication from arduino. Using nrf24l01 is that possible? The best scenario would be ...
7
votes
2answers
1k views

Why aren't ferrite rod antennas used in WiFi?

Does it have something to do with soft ferrite's low coercivity, still not low enough at gigahertz frequencies? See, I'm putting together high gain receiver antennas and transmitter antennas. Space ...
0
votes
1answer
57 views

RF - separate transmitter and receiver antennas for half duplex

i was wondering why is it for just half duplex systems, don't we have a dedicated transceiver and a dedicated transmitter antenna. ok, just hear me out... assuming we are using grounded monopoles, ...
-2
votes
1answer
44 views

Can radios in a router communicate each other [closed]

I am research scholar working in wireless mesh network. I have learned that each mesh router can have multiple radios/interfaces and each radio in turn support multiple channels. For eg:- two radios ...
0
votes
2answers
58 views

How can the 2.4GHz ISM band have 130+ channels?

I am a relative beginner regarding wireless communications protocols and I am looking into the protocols used by toy helicopters, in particular the Hubsan X4. According to more experienced people who ...
0
votes
1answer
34 views

What is a channel tap?

In wireless communication, I am confused about what people are referring to when they use the term 'channel tap.' Can someone explain the term or provide me a definition? Any help will be ...
0
votes
1answer
56 views

How to listen to radio communications from a transmitter?

I have two devices communicating at a frequency which I don't know. I want to listen to that communication so that I can replicate one of the devices and fool the other. Basically I want to reverse ...
0
votes
3answers
103 views

Can you use your computer to make a radio transmitter? [closed]

I was wondering, is it possible to oscillate the electronic signal emitted from the audio jack on a computer ? Because I would like to somehow create a simple radio transmitter just using my computer. ...
0
votes
3answers
122 views

How to build a simple LED transmitter and receiver

I'd like the distance to be about 1/10th of a mile; less distance will be fine if that's easier to build. What tools and parts may I need for this? I have plenty of LEDs lying around and I have ...
3
votes
2answers
213 views

Car radio output voltage

I am working on an amplifier for a car radio for a friend of mine. He is away for few weeks so I can't measure the radio output. That's why I am asking here, does anyone know, what's the ...
1
vote
1answer
95 views

How to build an FM transmitter and how does it work?

I have become interested in radio transmission and would like to know how to build an FM radio transmitter. When I search for information I either get a block diagram or a video of someone putting it ...
16
votes
12answers
3k views

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 ...
1
vote
1answer
56 views

Designing radios with gnuradio

I am looking at FM radio receiver designs others have created with gnuradio. There are a couple of signals questions I have after looking at these designs. The source (e.g. rtl-sdr) samples at a ...
1
vote
1answer
39 views

How to detect several agents within a radius, what is the best and easiest way to do it?

I have a room with 30 objects which may or not be present, and I want to be able to detect which objects are in the room. My first idea was to attach a RFID tag to each one of these objects and have ...
0
votes
2answers
44 views

Which characteristics of a Radio signal are involved to be selected by radio receiver? [duplicate]

the radio antennas receives millions of signals. how our radio selects the appropriate signal as it's input? which characteristics of the signal are involved for this selection.
1
vote
2answers
39 views

Shared antenna on multiple 2.4Ghz receivers

I want to use several 2.4 Ghz transcievers (not sure which IC yet, either Atmel AT86RF*** or TI CC) in order to build a simultaneous multi-channel sniffer. The transciever output is differential. I am ...
0
votes
1answer
28 views

Using RF for relative direction finding for short ranges (sub 10m)

I'm considering building a short-distance direction finder to determine the relative position of two objects. I want to be able to determine direction through other objects, which eliminates IR or ...
0
votes
0answers
33 views

Best RF frequency for my application

I need to design a device that can transmit an RF signal about 200 meters. The data transferred is very simple. One device simply has a button, that when pressed transmits a two-digit ID to the ...
2
votes
2answers
73 views

Data Whitening Block Diagram

I would like to understand this block diagram and how it relates to the formula: g(D) = D^7 + D^4 + 1 Supposedly this helps to generate a whitening word used within bluetooth radio, the empty boxes ...
3
votes
2answers
297 views

Does this simple RF transmitter circuit actually work?

I've come across this circuit a few times while searching for simple transmitter circuits, and decided to try it. According to this site, it should be transmitting at around 90Mhz. ...
1
vote
1answer
78 views

How much RF-interference does a typical desktop computer produce? How much does a metal case without windows reduce it?

It's fairly common now to see desktop computers in cases with large windows cut in the sides. I've always been under the impression that if unshielded, computer equipment will produce a lot of radio ...
-1
votes
1answer
236 views

What is the best and simple circuit diagram for a radio receiver to receive radio waves in Citizen's Band [closed]

I am building a two way radio system using the citizen's band in India. The transmitter is using a 555 timer IC clocked at a frequency between 26.957-27.383MHz to transmit AM waves. Can you please ...
0
votes
1answer
92 views

Making my own radio transmitter

So I have recently been interested in Radio electronics, and I have been looking around to buy a HAM radio transmitter,but they tend to be very expensive (and you learn nothing by just buying it). So ...
0
votes
2answers
122 views

Is possible to build -168 dBm amplifer?

we know that GPS receiver can reach sensitivty of -168dBm, and also it is possible to make receivers with similar sensetitvity can operate at another bands/frequencies . but I just want to know if ...
-2
votes
1answer
64 views

What Heinrich Hertz did different than Faraday

Now this wiki page says Heinrich Hertz is the person who found radio waves. And here, it describes how the experiment has done. He basically made first antenna. But years ago, Faraday found law of ...
1
vote
2answers
106 views

Filter for radio receivers

I am in need of an intermediate frequency (IF filter) for somewhere around 200 Khz as intermediate frequency. However, I know just the bare minimum of filter design ( learnt all that a couple of days ...
1
vote
4answers
258 views

High precision trilateration in a small space and without ultrasound

I need my robot to be able to find its position in a room with ±10cm accuracy. For that I have decided to place two radios right at where the door is and the third radio on the robot. The room is ...
-2
votes
1answer
91 views

Radio signals blocked by red bricks / aluminum insulation

Do red bricks home/building and aluminum insulation diminish the strength of radio signals?
1
vote
1answer
107 views

Exchanging packets over an nRF24L01+

I have two nRF24L01+ chips each attached to a Bus Pirate. I'm trying to write some code to test exchanging packets between them, at first entirely on my laptop before I eventually move out to an AVR ...
0
votes
0answers
23 views

Transmission using different frequencies [duplicate]

Consider three devices and a base station. Communication is only through radio waves. The devices are equipped with a simple radio that enables them to send and receive information from base station. ...
0
votes
2answers
72 views

communication 101 [closed]

I have a couple of really basic questions. (1) When a device(Device 1) communicates to another device(Device 2), do the devices have to operate in the SAME frequency for the data transmission to take ...
1
vote
0answers
56 views

Which communication protocol to use [closed]

Consider two devices having a basic radio transceiver (and use the same frequency) and a base station which uses a different frequency radio. The data from base station should be broadcasted to both ...
2
votes
2answers
82 views

Multipath fading in mobile radio systems

Here is the problem that left me thinking: "In a mobile radio system (e.g., cell phones), there is one type of degradation that can be modeled easily with sinusoids. This is the case of multipath ...
5
votes
2answers
131 views

How Reflex Klystron works

I have a doubt on how exactly a reflex klystron works(as an RF source). In wikipedia it says that, The electrons are fired into one end of the tube by an electron gun. After passing through the ...
1
vote
1answer
111 views

Which one of these transistors is equivalent to 2N918 NPN?

This is an FM radio receiver. Q1 is 2N918 NPN transistor but it is not available for me. Which one of the following transistors is more equivalent to Q1 ? BC547 TL431 s8550 s9014 2n5401 ...
1
vote
1answer
104 views

Help with a RF reciever circuit

Recently I have been working on a basic RF receiver, but my efforts so far have proved fruitless. I designed the following circuit based of of previous research into the topic. According to what I ...
1
vote
1answer
113 views

Crystal radio (AM receiver)?

I've made this circuit on a breadboard. It doesn't work properly. I hear the sound of an oscillator (similar to the sound of 555 timer). I changed C6 and L1 to change the frequency but I hear the ...
2
votes
1answer
128 views

A question about resonance and crystal radio?

This is a circuit of crystal radio transmitter. I've tested it, and it works properly. but I can't understand everything in this circuit... L1 and C5 make resonance frequency, Would you tell me if ...
0
votes
4answers
101 views

How to detect Resonance?

I've made many RC circuits and RLC circuits ( series and parallel resonance). I want to make sure that these circuits work and make resonance, but I don't have CRO device. Is there any way to detect ...
1
vote
1answer
390 views

Identifying a 3-Terminal Component (probably some sort of magnetic device?)

I am trying to identify this component from a circa 70s AM/FM radio. It was attached to a flip clock, which makes me think that it is a magnetic device responsible for the "flipping" action of the ...
1
vote
1answer
162 views

Basic FM circuit

I have been messing around with a basic FM transmitter circuit, and I want to have a better explanation on how it works. I have searched around and found nothing. Can someone please explain how the LC ...
1
vote
1answer
119 views

Determine the working frequency band of unknown RFID chip

I have a passive RFID chip from which I would like to scan the ID. I have a standard USB RFID Reader, but this doesnt print out anything. This reader scans the 120–150 kHz range, so the chip must ...
1
vote
2answers
160 views

How can I turn pulsating DC (square wave) from a 555 IC timer into an ac square wave?

I am trying to create build a morse code transmitter. I know that morse code is sent at 500 KHZ so I set my 555 to spit out pulsating DC in a square wave with 9 volt peaks. But I am unsure wether ...
9
votes
7answers
2k views

Schematics for a simple radio transmitter that can be built only with passive components?

Fantasized in some of the survivalist, post-catastrophic novels, movies or docudramas is the radio built only with handcrafted or scraped components. Beyond the popular appeal of this stories, I ...
0
votes
2answers
74 views

Tuning the radio receiver

I am trying to understand how exactly to tune the Superhet receiver. In my simulations, I have attached to the initial frequency mixer---> A local oscillator and an AC signal source to model the ...
0
votes
1answer
163 views

How to tune a radio receiver using a crystal oscillator?

I'm building my first radio receiver (a simple Ramsey HR-40 kit). The "Alignment" section of the instructions requires that I have some other device which I tune my receiver to. Since I have no such ...
0
votes
1answer
78 views

Radio Receiver IC

I am a Junior EE student that is interested in putting together a small radio receiver project for fun and to get some general practice with design. I have found these receiver chips from Silicon Labs ...
3
votes
2answers
131 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, ...
1
vote
2answers
171 views

Custom push-to-talk button on a handheld two-way radio

I want to make my own PTT for this two-way radio. How can I determine how it is realized? I've figured out that the two "potential rings" with the biggest diameter on the 3.5mm and 2.5mm plug are ...
3
votes
2answers
252 views

AM and FM reception with the same antenna

I'm designing a radio with the Si4735 chip to use in a car, and I want to use the existing FM antenna for both FM and AM reception. I'm not sure how to go about this, exactly. How would I go about ...