Consider also the rf tag.

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1answer
73 views

Radio signals blocked by red bricks / aluminum insulation

Do red bricks home/building and aluminum insulation diminish the strength of radio signals?
-1
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0answers
50 views

How to make a good Walkie Talkie [on hold]

I am planning to build my own two-way communication mainly for bike rides in INDIA that I would fit in my and my friend's helmets. I am looking for high quality (not very high but clearly audible and ...
1
vote
0answers
17 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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votes
0answers
96 views

Would anyone explain this circuit? [duplicate]

I know that the transistor works as an amplifier but I can not understand why it is connected this way. I'm a beginner in electronics and I just want an explanation for this circuit (especially the ...
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
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2answers
61 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
46 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
49 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 ...
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votes
0answers
63 views

Interfacing MP3 player audio output to a simple FM Transmitter

I found this circuit on the Internet that I'd like to modify. Rather than a microphone as the input I'd like to take the output from an MP3 player so I can play music remotely using this circuit: ...
5
votes
2answers
64 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
50 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
95 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
80 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
108 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
76 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
377 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
111 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
58 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
96 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 ...
8
votes
7answers
1k 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
56 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
76 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
58 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
90 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
74 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
221 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 ...
3
votes
0answers
131 views

How to avoid regulatory approval regulations, when chosing a RF module?

I've been trying to implement RF capabilities into my projecto, but I don't want to pay thousands of euros to get an ETSI certification in case it gets into production. I know that if I get a complete ...
2
votes
1answer
233 views

Why does this regenerative receiver not just turn into an oscillator?

I'm trying my hand at making a radio transmitter and receiver and I'm not sure exactly how this receiver works. I understand its a continuous wave receiver which is good for on/off transmission. I'm ...
2
votes
2answers
139 views

Designing shortwave radio receiver

I was building a receiver circuit ( superhet) for shortwave radio, primarily for 20m ( 14mhz) band. The circuit uses 3N211 or 40673 mosfet for mixer. However I have only these components available at ...
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votes
1answer
66 views

Separate antenna for radio transmitter and receiver

I am building a HAM radio. Do I need a separate antenna for transmitter and receiver? I will be using 20m band and voice communication (No Morse code). My primary requirement is that I should be able ...
0
votes
2answers
96 views

What power is measured by a spectrum analyzer?

Is the signal level that is shown in a spectrum analyzer power of the signal being measured. If yes then what power is it: average power, true power or peak power? Also when using a power meter for ...
1
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2answers
174 views

Low volume from 1960's radio

I have a 1960's Philips all transistor radio which I restored recently and replaced two of the AF11x PNP germanium transistors on the mixer/oscillator and IF amp stages. After these replacements, the ...
3
votes
2answers
327 views

How do radio stations broadcast information?

I have noticed that modern FM radio stations broadcast simple text information about them. While this does not affect the analog sound, it can be decoded by most modern FM receivers, including my ...
2
votes
0answers
45 views

Is it possible to replace a CC2500 with a CC2531?

I have a working Arduino->CC2500 configuration, and I'd like to know if it's possible to replace that with a CC2531 USB dongle. Does the CC2531 have the ability to form the correct packet structure ...
0
votes
1answer
67 views

Using filters to reduce bandwidth of received signal

I am doing some radio work, and I assume you can use a bandpass filter to reduce the bandwidth of a received signal. The application is modifying schematics for a FM broadcast receiver to a 5-25 kHz ...
2
votes
2answers
125 views

Down-Conversion of RF signal

I have a basic question about down-conversion of RF-signals. The ideal scenario is described as follows. Given a RF-signal (coming from an antenna), i.e., a real-valued function x(t), and given a ...
1
vote
1answer
103 views

MCU selection for developing a baby monitor

I'm developing a project which involves a device (stationary, connected to mains) making some simple calculations and processing, and then sending an alarm (a simple message to trigger a vibration ...
4
votes
2answers
324 views

Why does my mic behave like an antenna only when I touch it?

I recently built this mic amplifier circuit (source): The output is connected to a speaker, but it's not exactly working as intended: I can only hear myself at the output if I blow hard into the ...
2
votes
3answers
282 views

Bit rate in function of radio frequency

I would like to transmit data over the ionosphere with a specific frequency (that will enable the radio waves to bounce on the ionosphere), this frequency might be about 30 MHz. I am wondering how ...
0
votes
1answer
242 views

Can a cell phone's IMEI be tracked even if it is switched off? [closed]

I'm doing some research for a project and I have a doubt. In a cell phone, along with the clock, is a part of the cell radio also on when the phone is switched off? And can a cell phone be tracked ...
1
vote
1answer
154 views

How to find out what radio frequency is being emitted?

Let's say I have something akin to a garage door clicker. How can I discover the frequency and message it sends with no other information on the device? I want to decode this to the electrical ...
-3
votes
1answer
131 views

Which modulation does radio walkie talkie work on? [closed]

On which radio band does walkie talkie work on? Is it amplitude modification, frequency modulation, or short way modulation?
1
vote
3answers
80 views

Tuning a radio wave receiver

Variable capacitors are used in tuning many circuits of radios. I read the theory of basic tuning and resonance frequency. What I understand by changing the capacitor we change the resonance frequency ...
0
votes
1answer
152 views

Streaming UHF/VHF/AM/FM over IP

I am working on a project that can stream TV and Radio signals over IP. I found a device to capture the signals and send them over IP realtek-rtl2832u but I am ...
2
votes
2answers
474 views

When powering a Nrf24L01 hooked up to an arduino by external battery does ground still go to the Arduino ground?

So as mentioned in this article, the radio chip might have power problems and an external power source is recommended: http://arduino-info.wikispaces.com/Nrf24L01-2.4GHz-HowTo My question is for the ...
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votes
1answer
263 views

How to measure distance using radio waves? [closed]

Have you seen http://www.youtube.com/watch?v=CvZ4_SIAxDY I need a similar circuit to do the same. There are two module. Module A and B. A sends to B and B returns signal to A. How to find the time ...
3
votes
2answers
188 views

How small can a radio transmitter be?

Lately, I've heard about a fascinating new technology called DNA Origami, where incredibly tiny machines are folded out of DNA. Using CAD software they are able to build all sorts of interesting ...
0
votes
0answers
77 views

Reason for choosing particular frequencies for ISM bands

There is a number of ISM bands, including the widely used 2.4 GHz. But which were the reasons for the FCC and ITU to pick those bands? I suppose, that with 2.4 GHz there's a connection with water ...
2
votes
1answer
201 views

How does a cube sat communicate with ground station with a 1w antenna

I heard that cubesat signals can be received with a hand held radio. Its confusing me that how a 1 metre antenna radiating 1watt energy can simply be received using hand held radios. I am designing a ...
4
votes
3answers
240 views

Full duplex shared frequency radio?

Normally shared frequency analogue1 radios (CB, aviation, etc.) can't receive when transmitting, because the signal being transmitted is much louder and will jam any signal from different transmitter. ...