Questions on a set of equipment used to generate and transmit electromagnetic waves carrying messages or signals, esp. those of radio or television.

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0
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1answer
32 views

How did four-course LF radio navigation ranges have their beams other than at 90° / 180° angles?

The four-course Low Frequency Radio Range system used for aircraft navigation (in the US and elsewhere) in the 1930s and 1940s used a pair of directional antenna (with figure-of-8 shaped radiation ...
0
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2answers
54 views

Transmitter and receiver problems [closed]

Hi I am a construction site manager with very little knowledge in electronics. I have recently invented a new site safety device which involves the use of multiple transmitters and receivers. I ...
0
votes
1answer
85 views

Maximum range of 27 MHz ISM band NLOS radio broadcast

What is the maximum range of a 27 MHz ISM band when transmitting at full power? I am interested in general situation for US and EU but that will go back to the power limits allowed. My country (CZ in ...
2
votes
2answers
142 views

Boost the signal of an FM transmitter using an “emitter follower” transistor [closed]

EDIT: I've seen an alert under my question: “Please clarify your specific problem or add additional details to highlight exactly what you need. “ Maybe this is due to the fact that I'm not very good ...
0
votes
1answer
35 views

FCC cert - inactive transciever

Does the product on USA market with inactive transmitter (2,24 GHz) need the FCC certification? We are going to use Tx/Rx module, but the transmitting function will be software disabled.
4
votes
3answers
321 views

How can I reproduce ambient EM fields inside a Faraday enclosure?

I am part of a research team looking at the possible effects of EM fields on psychological function. The experiment calls for participants to perform a series of tests while inside a Faraday tent that ...
3
votes
2answers
67 views

Difference between ultrasonic transmitter sensor and ultrasonic receiver sensor?

What is the difference between ultrasonic transmitter sensor and ultrasonic receiver sensor? Can an ultrasonic receiver sensor be used as an ultrasonic transmitter sensor or vice versa?
-1
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2answers
47 views

Turning LED lights on/off based through any wireless means

I've spent several hours researching this website for an answer to my question. The problem is i don't know the terminology or anything. So if you know the answer please treat me as an individual with ...
3
votes
1answer
89 views

Does thhis crystal circuit works?

I need a tiny oscillator circuit for testing an application. Now I haven't much experience in creating oscillators so I would like to use this Collpits-circuit: I only need the carrier wave so I ...
-1
votes
2answers
189 views

Building an fm transmitter broadcasting simultaneously to all fm frequencies

I would like to build an FM transmitter that transmits a signal to all fm frequencies simultaneously, so that any nearby radio tuned to any frequency can receive this signal. Is it possible to do this ...
0
votes
1answer
72 views

Switching on Power to 433MHz chip

I have this 433 MHz transmitter attached to my Arduino 5v Vcc pin. I asked this question so I could deliver 12v to the transmitter chip, effectively boosting the transmitted power output, allowing me ...
1
vote
3answers
133 views

Are the same type of antennas used for receiving and transmitting?

Short version: Is the same antenna type used for transmitting as is used for receiving if the frequency is the same? Long version: My garage door opener uses 433 MHz to receive signals from the ...
0
votes
2answers
46 views

Transceiver and RF Emissions (Unintentional)

My question is simply what is RF emissions (unintentional) and how does it relate to a device (such as a smart phone) which contains a transceiver or transmitter (baseband IC) ? Which part of a RF ...
0
votes
1answer
84 views

Hacking an RC car controller to implement a joystick (PWM)

My RC car controller (transmitter) has only 4 buttons (left wheel forward /backward, same for right) I want to implement a joystick using Arduino. The Arduino will use PWM on the transmitter ...
2
votes
1answer
48 views

Questions about FM Mic Kit Schematic

I'm currently building an FM Microphone kit and I'd like to understand its operation before physically putting it together. The documentation only provides an overview of some aspects and provides no ...
1
vote
1answer
194 views

315 MHz Reciever/Transmitter Raspberry Pi

I bought a receiver and transmitter (I can't find the link, but it says FS1000A and LR1 315.00 on it). I also have a set of remote controlled wall outlets that operate on 315MHz according to the FCC ...
0
votes
1answer
121 views

RS232/RS485 Converter Circuit Receiving Problem

I'm trying to make an RS232/RS485 converter circuit. I used a circuit from http://airborn.com.au/layout/232cnv/232to485.html site and i changed some components on that circuit. Then I established my ...
-2
votes
1answer
81 views

Wiring the antennas together in RF link 315Mhz RX and TX

I am using a 315Mhz Transmitter and Receiver RF link kit between two arduino. What happens if I wire the antennas of both RX and TX to both ends of a 1 meter long metal wire? Will using a conductor ...
1
vote
2answers
47 views

Common-Mode Voltage

I have an application which is using a differential transmitter to transmit a video signal(PAL).Transmitter is placed in a remote device which is connected through a long cable.The device is powered ...
0
votes
1answer
36 views

Locating the Origin of 2.4GHz RF Transmissions

Is it possible? How would it work? Consider IEEE 802.11 (aka.Wi-Fi); for instance. There's such an incredible amount of devices out there, measuring and reporting WLAN AP signal strength (RSSI, RCPI, ...
1
vote
2answers
128 views

Is there anyother way to construct an FM transmitter

I recently built an FM transmitter that uses a combination of coil and capacitor as an oscillator to generate the carrier frequency. I built this transmitter: Now my problem is that I find it ...
1
vote
2answers
142 views

Do commercial AM radio stations broadcast a carrier?

A possibly dumb question: I'd like to know if commercial AM radio stations broadcast a carrier tone along with signal sidebands. To ask my question is a different way; if I could measure (view) the ...
0
votes
1answer
54 views

Low-Frequency Magnetic Transmitter

I want to design a magnetic transmitter to detect a device which will be underground (1m to 7m) from surface, so I started to look at a solution and I find that a magnetic transmitter will work ...
0
votes
2answers
33 views

RFM only works if i touch power supply line

I have a small system with a ATtiny84 and an RFM12B module that transmits data. The thing is it only transmits when i touch both GND and +VCC.. no matter what component it is on. Do i need mere caps ...
-1
votes
1answer
47 views

Location transmitter [closed]

I want some advices about a radio transmistter,actually this radio trasmitter is more a location transmitter which transmits at about 512Hz.I want to know how could i design a transmiter and a ...
3
votes
3answers
727 views

FM transmitter design?

I stumbled across a relatively simple FM radio transmitter online. Credit: makezine.com I wanted to understand how it works (it is called "super simple" on the website), but several hours I have ...
0
votes
3answers
181 views

555 AM transmitter

I looked on instructables and I found an interesting(at least for me) AM transmitter made with a 555 timer which acts as the oscillator:http://www.instructables.com/id/555-AM-Transmitter/ Is this ...
39
votes
8answers
5k views

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 ...
0
votes
1answer
23 views

ETSI Tx Power standard for short Range Devices. I am Confused

I came across the European Telecommunication Standards Institute (ETSI) standard for non specific Short Range Devices which is documented in EN 300.200 . On page 28 under Section 7.2.3 with Heading ...
0
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1answer
79 views

How to build a transmitter using a VCO module

this question is the consequence of my previous questions, since I am learning how RF transmitters works. In past I have also built some oscillators (using little transistors and a bunch of ...
0
votes
2answers
291 views

Make an RF transmitter: classic transistor oscillator or VCO module?

This question is about pros and cons of making an RF transmitter (eg in the FM band) in the classical way (eg. with a "transistor based" oscillator circuit, like this one which is very classic and ...
-1
votes
2answers
46 views

How to solve Power Density Function?

How to solve this problem: A radio receiver needs $$ 1 \textrm{ nW/}\textrm{m}^2 $$ of power density function, how far away from a 1-watt point source will it continue to work?
2
votes
3answers
261 views

Transmit power vs. Transmission power, is there a difference?

I was reading a scientific paper, and the authors sometimes use the term "transmit power" and sometimes "transmission power". Is there a difference in terms of correct English usage? Examples: ...
0
votes
1answer
197 views

Multichannel RF transmitter design for 315MHz and 433MHz

first time designing RF, so pardon my ignorance. I want to design a ASK/OOK transmitter board operating on both 315Mhz and 433MHz ISM band frequencies. I have a MCU onboard that generates the data to ...
0
votes
1answer
61 views

Changing the port values inside the loop (8051)

I am using RX/TX module an ht12d/e for my project. I will make it short, in my program i am making a packet of data and sending it and the receiver is receiving it synchronously. The receiver is set ...
1
vote
1answer
204 views

Merging right & left signals to mono with aop?

Sorry for my english i'm a young french. I want to design an audio transmitter to connect my pc to my Hi-Fi without Jack cables. For now i just want to send a mono signal because sending a stereo ...
2
votes
3answers
202 views

What are the basics I need to know to power LEDs with RF at a range of 30 feet?

I would like to light up a path in the woods with hundreds of LEDs using RF. The idea is that I would carry a RF transmitter powerful enough to light LEDs. As I approach the LEDs would get brighter, ...
0
votes
2answers
163 views

How do I implement TDMA with basic 433 MHz transmitter receiver pairs?

Is it possible to use TDMA or some kind of time synchronization / pseudo random coding for a number of transmitters so that they can be interfaced with a single master receiver without jamming?
1
vote
1answer
155 views

Can I transmit in the ISM band without a ham radio license?

I recently purchased a HackRf SDR, which has transmit and recieve capability. I'm debugging a 2.4ghz wireless module, and being able to transmit to it using the hackrf would be very helpful. Since ...
3
votes
1answer
142 views

Best communication option for multiple arduinos?

my father and I want to develop a cow pedometer to measure cows activity. The idea is that if you can measure a cow´s activity you can detect when she enters heat. Detecting heat with sensors will ...
0
votes
1answer
65 views

How much power does a phone consume each time it ping its SIM's ID to the nearest cell tower? [closed]

I am trying to build a device than can be tracked through the cellular network. Like a phone, for every few second the device will ping its identity to near by cell tower, which will inform the Mobile ...
-2
votes
1answer
551 views

Using HT12E/D with RX/TX 433Mhz modules

i have ht12d and ht12e ic's and rx tx 433Mhz modules. i arranged the ht12e to the output port of Microcontroller and connected the ht12e to transmitter and similarly to the recieving side. is it now ...
0
votes
2answers
81 views

How to transmit a signal to a reciever over 50 meters?

I'm studying at a technical college in Denmark, and I'm doing an exam project involving emergency calls for elders. I'm currently trying to build a solution, but it involves a transmitter which can ...
0
votes
2answers
238 views

Arduino along with radio tx/rx

I'm thinking about a project similar to the home-automation systems etc... Few problems came in the way, The cost of the Arduino radio receivers/transmitters is huge, especially if I need few of ...
-1
votes
1answer
73 views

How do cell phones modulate transmission data

Is it digital, as in the the phone transmitter is turned on and off corresponding to the bits, or is it FM or AM? at what frequency? and how is it that they can transmit what appears to be over large ...
0
votes
1answer
85 views

Use 555 Timer Voltage Doubler to Increase Range of Transmission

I have seen a number of 555 timer voltage doubler circuits. I am building a fm radio transmitter like this one: I understand that the higher voltage the farther the transmission range. Would this ...
0
votes
1answer
567 views

Use Potentiometer to change frequency in FM Radio Transmitter

I know that in most circuits you use a tank circuit consisting of an inductor and variable capacitor in parallel to generate different frequencies like this one. However since most cheap trimmer caps ...
0
votes
1answer
279 views

Use Preformed inductor instead of coil for FM Transmitter

I want to build this transmitter: The inductor in the schematic says 0.1uh so I figured I could get some of these and use them instead of making my own like it describes in the picture. I would be ...
0
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1answer
458 views

2n3904 vs. Pn2222A for FM Radio Transmitters

My question is which is better for transmitting an audio signal on the common 88 - 108 fm band: the common 2n3904 NPN transistor or the PN2222A NPN or are they interchangeable. I have seen a lot of ...
0
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1answer
469 views

555 timer as FM transmitter vs. Tank Circuit

This site seems to suggest the use of the 555 timer in astable mode to generate frequency modulation from a source. The typical transmitter uses a tank circuit with an inductor and trimmer capacitor ...