Consider also the rf tag.

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2
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1answer
26 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
votes
0answers
58 views

Modifying AM radio to receive CB/CW/HF 27Mhz signal [on hold]

I'm working on a project that calls for pre-used radios to be modified to detect an AM CB radio broadcast. I've never done any work with radios before, and have been trying to hunt down any sort of ...
1
vote
2answers
40 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
201 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
89 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
201 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
96 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 ...
-1
votes
1answer
48 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
84 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
vote
1answer
114 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
325 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
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0answers
36 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
58 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
111 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
100 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
310 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
251 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
137 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
119 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
108 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
67 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
104 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
287 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 ...
-1
votes
1answer
142 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
157 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
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0answers
74 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
150 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
230 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. ...
3
votes
1answer
56 views

Radio Transceiver bulkhead connection and Ground

I have a problem regarding mounting of RF transceiver. The main board inside metal cabinet is floating and when I check the antenna SMA bulk connector its outer case has a connection to circuit ...
0
votes
1answer
100 views

Making an AM radio with a silicon diode

I've been working a few days on this and have still come up with nothing. I am trying to make an AM radio using a silicon diode, but all of my attempts have failed. I believe my latest attempt most ...
0
votes
0answers
50 views

No radio signals with antenna

I have an antenna I made with about 2 feet of insulated copper wire, stripped at one end. The antenna is connected to the positive side of a 1000uF capacitor, using this circuit. I am using a 741 ...
2
votes
1answer
112 views

How is signal strength calculated?

How is the signal strength calculated in case of cell phones ? How will the signal strength be calculated in case of WiFi networks ? I am not certain if the question I am asking is the same as QoS ...
11
votes
1answer
260 views

Why does the 802.11 wifi spec allow for 11 channels?

The general wisdom is that it is better to only ever use channels 1, 6, and 11 as they are the only three non-overlapping channels for 2.4ghz wifi (in the US), and two adjacent networks on the same ...
0
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1answer
35 views

Know the transmission speed between PICAXEs with Radio module

I was wondering if I could know the transmission speed between 2 PICAXEs using an Radio Module. At the moment I tried to send data between 2 PICAXE 40x2 only with the 433MHz Radio Transmitter. The ...
1
vote
1answer
75 views

Radios and Power [closed]

RF newbie here. Lately I've been experimenting with RF. I built some simple oscillators, managing to get a tank circuit working as well as buffering the 1 megahertz output of a tin can oscillator. ...
7
votes
1answer
232 views

Radio Transmitter using Crystal Oscilliator

I am on the mission to control my RC car using arduino. The simplest way I thought of doing this is to add arduino outputs into the transmitter. Long story short I wanted to learn more about how these ...
0
votes
1answer
95 views

sending data with cc2510

Hy, I'm trying to send simple 1 Byte package with cc2510dk-mini. The idea is to press button on on device and the led on the other lights up. I'm stuck with the problem, when I try to send data, radio ...
1
vote
2answers
282 views

NRF24L01+ Power Amplifier -dBm options to milliWatt

From the datasheet for these module I have the folowing power settings available (listed form highest to lowest), I need to know what they equate to in milliwatt, as in Australia maximum 2.4ghz ...
4
votes
1answer
202 views

Properties of a WWVB Receiver

In this article the author dissects a radio-controlled clock that syncs with the NIST transmitter, WWVB, in Colorado. The radio receiver seems to be a single integrated unit: Of special note is ...
1
vote
1answer
184 views

Smoothing and decoupling power source input

I am transforming an old battery-only radio so I can connect it through a DC input. I found an earlier model diagram that includes the DC input (picture attached). I have connected a 18 V DC source ...
2
votes
3answers
106 views

What's the best shape and material for my Wi-Fi range booster dish?

I want my wireless LAN to be available in an apartment that is 459 feet (140 m) across. I'm thinking about putting a router (bridge) that has an omnidirectional antenna on the roof of my apartment, ...
2
votes
2answers
140 views

Intercept SPI of RC helicopter controller

I've got this radio communication with an RC helicopter. I found that the RX on the heli is using an AVR MCU and a CYRF6989 2.4Ghz chip to communicate with the controller of the heli and translates it ...
1
vote
1answer
123 views

Loudspeaker transducer FCC certification?

Is FCC certification necessary for speaker transducers that are sold as assembled units in their housings? I found information on active speakers needing fcc certification, but what about passive ...
0
votes
1answer
247 views

How do “Wire Wound Chip Inductors” work [closed]

I have a police scanner that has a couple of modules in it. One of these modules is marked 390G (Data Sheet) I can't see the other modules number but it looks identical. I know they are NOT the ...
0
votes
2answers
93 views

How to show field strength varies as 1/r

This is a question, from a radio amateur, that should have a straightforward answer: but I cannot find one on the Web. Is there a robust but simple explanation, not needing advanced maths, as to why ...
6
votes
1answer
213 views

How can this FM transmitter modulate?

simulate this circuit – Schematic created using CircuitLab This is a minimalist FM transmitter I've found from http://www.talkingelectronics.com/projects/Spy%20Circuits/SpyCircuits-1.html ...
3
votes
1answer
84 views

How does pseudo-random noise increase DCF77 accuracy

A few years ago the Germans added a pseudo-random noise signal (from a LFSR) to their time reference DCF77. I heard this should allow you to get a more accurate signal at the receiver side. But the ...
0
votes
1answer
54 views

Screen of a mobile phone inside something [closed]

As an image for a speech I want to be able to shield of the coverage of a mobile phone. I thought of putting it in something. So I grabbed the stewing pan made of cast iron from the kitchen. ...
2
votes
1answer
136 views

What RF protocol do wireless mouses and keyboards use to communicate?

I'm designing a device which uses Bluetooth 4.0 (Low Energy) and I noticed how hard it is to achieve decent battery life, but the average mouse or keyboard lasts months/years on two AA batteries. I ...
3
votes
2answers
119 views

How is mobile communication(between pilot and ATC ) made possible from airplanes?

I have heard that communication using mobile phones begins to degrade when used on a vehicle moving at speeds above 200 km/hr due to doppler effect as described here (p-22). How is this limitation ...