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34 views

Superheterodyne receiver with voltage controlled oscillator

I'm new in electronics and I want to create a FM receiver that performs a product of the received RF signal and a local signal (the local signal is also frequency modulated with a Voltage Controlled ...
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3answers
264 views
+100

Radio wave interference

While studying radio electronics I stumbled across a small article about wave interference on the same frequency. The article was very simple explaining that if there a stronger emitter on the ...
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2answers
42 views

How dBuV value changes with distance?

I've got an emissions source that's designed to generate a peak at a certain frequency that when measured by an antenna 3m away gives a value of X dBuV. If the emissions source if moved closer to ...
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2answers
52 views

what is the maximum range of citizens band radio computation

i have been computing the maximum distance for a citizen's band radio. i don't know if my computation is correct because the answer is so large, appx. 280000km. what do you think is wrong with my ...
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0answers
23 views

Problem with damanged radio transceiver

I'm developing a 2.4Ghz mesh and I've a problem with MRF24J40MC transceivers being damaged. The exact issue is that the transceiver can't receive incoming data unless the transmitter is very close, ...
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1answer
64 views

channel seperated communication in RF

In RF communication the carriers such as 950MHz, 133MHz are available under 1 GHz. If there are 50 devices using the for example 433MHz carrier, then how could large number of devices talk to each ...
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33 views

Several RF transmitter and receiver circuits work without interference

I need help or giving me any approach to make transmitter/receiver circuits which they will be in the same range, but every pair (Tx, Rx) works on a precision frequency spacing without any ...
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1answer
59 views

Should I use a passive or an active filter?

simulate this circuit – Schematic created using CircuitLab I need to design an am receiver as a project. On the front end I have three modules; BPF1 the "roofing filter" or the ...
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0answers
47 views

Amplitude modulation using mixer SA602AN

-----------EDIT-------------- I solved the problem using a coupled inductor at the output. Now i got a nice am wave. Thanks for your contribution. -----------EDIT END---------- i've got quite ...
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2answers
101 views

What RF attentuator would be used for the HackRF?

Background info: The HackRF is an SDR Radio capable of receiving and transmitting frequencies from 10MHz to 6GHz. Michael Mossmann, the creator of the HackRF, states in his wiki that: The ...
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0answers
32 views

Connect CB Microphone to Smartphone

I'm planning to use an Android smartphone as a realtime voice effects processor with my CB radio. I did a little internet research about the way Android devices detect a connected headset and found ...
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2answers
96 views

I can not receive radio waves using LM386?

I've made two different circuits to receive RF using LM386 but they doesn't work. I've changed the values of C2 and L1 to change the frequency. I've also changed the gain but nothing happens. The ...
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0answers
80 views

Is it possible to make a device that will transmit a sound\suppress my neighbour speakers?

Let's say, I've a highly inadequate, impudent neighbor who is listening to music very loudly. I've seen on the Internet that's there's a possibility to transmit your own audio to a neighbor speakers ...
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3answers
355 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 ...
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2answers
2k 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 ...
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1answer
85 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, ...
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2answers
74 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 ...
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1answer
41 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 ...
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1answer
59 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 ...
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3answers
115 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. ...
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3answers
151 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
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2answers
239 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 ...
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1answer
171 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 ...
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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 ...
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1answer
58 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 ...
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1answer
42 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 ...
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2answers
49 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.
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2answers
43 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 ...
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1answer
31 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 ...
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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 ...
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2answers
82 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 ...
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4answers
399 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. ...
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1answer
91 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 ...
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1answer
304 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 ...
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1answer
105 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 ...
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2answers
125 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 ...
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1answer
66 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 ...
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2answers
118 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 ...
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4answers
267 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 ...
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1answer
93 views

Radio signals blocked by red bricks / aluminum insulation

Do red bricks home/building and aluminum insulation diminish the strength of radio signals?
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1answer
125 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 ...
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0answers
24 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
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2answers
74 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 ...
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0answers
58 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
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2answers
97 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
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2answers
150 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 ...
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1answer
131 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 ...
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1answer
107 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 ...
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1answer
121 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
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1answer
133 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 ...