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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11
votes
7answers
1k 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
16 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
votes
1answer
31 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
45 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 ...
0
votes
0answers
40 views

433MHz transmitter and receiver pair doesnt work [migrated]

I have a pair of 433 MHz transmitter and receiver: Transmitter is connected to Arduino pro mino, receiver to Arduino uno r3. Output of receiver on serial looks like that(it doest change much): ...
-1
votes
2answers
27 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?
0
votes
0answers
21 views

Mimicking the signal from rx to tx for efm32

As stated in the title, am looking for a smart way to do the stated, i.e, I want to send back the signal I'm receiving, and read it while it passes through my buffers and process with that info... in ...
2
votes
3answers
187 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
0answers
37 views

wireless on/off switch for LED using RF transmitter reciever

i wanted to switch on an LED using an RF transmitter receiver like we can see in this video (https://www.youtube.com/watch?v=jeRtyOgf0mI), although i do not want the morse code application, i just ...
0
votes
1answer
40 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
34 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
50 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
124 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
67 views

How to implement TDMA with basic 433MHz transmitter receiver pairs ?

Is it possible to use TDMA or some kind of time synchronization / psuedo random coding for a number of transmitters so that they can be interfaced with a single master receiver without jamming?
0
votes
1answer
88 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 ...
0
votes
0answers
44 views

Ultrasonic sensor pair operation

I have had success with using SR04 to measure distance from the SR04 location to nearest obstacle. Now I want to be able to measure distance of two mobile location one mounted with ultrasonic ...
3
votes
1answer
127 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
52 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
228 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 ...
1
vote
2answers
65 views

Intercom Malfunction [closed]

I'm an electrical engineer, but I didn't pay close enough attention in my Comms Systems class apparently because this baffles me. Hoping someone else has a better guess about what is going on and/or ...
0
votes
2answers
70 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
112 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
58 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
57 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
146 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
60 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
votes
1answer
179 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
votes
1answer
151 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 ...
1
vote
1answer
97 views

Transmit electrical signal across human body [closed]

Is it possible to transmit and receive an electrical signal SAFELY using the human body as a medium? For example, I would have a transmitter of some sorts in my left hand, and a receiver in my right. ...
0
votes
1answer
66 views

Timed Infrared or Infrared PWM Signals

We are trying to have a moving IR receiver pickup a specific IR-led for a range of IR-LEDs. The options we're looking at : Send and unique pwm signal from each different led, the moving object ...
0
votes
2answers
388 views

How to remove the static sound in an fm transmitter

Hi I have a school project and I used the schematics from this website for our FM transmitter. Its actually working but its hard to recognize the music being played because of the static, also does ...
0
votes
0answers
58 views

Transmitting data over Long range ,using a Low Power Circuit

I Have Been Designing a BOT That Would Travel Along the Pipeline And Detect Leakage Using Ultrasound Efficiently,And Locate The Position of Leakage Using A GPS MODULE using the Arduino,I have make it ...
1
vote
1answer
175 views

Boost a weak AM transmitter

I've made this simple AM transmitter: http://makerf.com/posts/fun_with_crystal_oscillators_part_3 The author of this circuit, claims that would be possible to extend the range of this transmitter ...
0
votes
2answers
200 views

Is wireless power transfer by induction at 60Hz possible, or does the frequency need to be changed?

I want to build a wireless power transmitter that works over a very short distance. Can I use my line voltage(120V at 60Hz) through the primary coil to induce voltage into a secondary coil about 1/4" ...
0
votes
1answer
36 views

Looking for a LED transmitter/receiver package(or group of components)

I am trying to design a system that utilizes 355nm and 370nm LEDs. I want to keep their intensity stabilized at a certain value, so I want to create a feedback loop. I am using these LEDs as ...
1
vote
0answers
78 views

How to convert laptop to charge wireless

I am wanting to charge my laptop using Qi wireless charging transmitters and receivers. Setup: The laptop battery is a Li-ion belonging to a Sony Vaio Flip 15A (output: 15v 3.17 Amp, input: 19.5v ...
0
votes
0answers
23 views

T/R switch for single element material thickness testing (-200V pulses)

Our non destructing ultrasonic inspection design now has two crystals, one for transmitting and one for receiving. We would like to have only one crystal for transmitting and receiving. This is common ...
1
vote
1answer
62 views

How to adjust or obtain different IR Transmitter's distances?

I would like to recreate a infrared concept used by in the vacuum cleaning robot's charging station. I would like to use 3 infrared transmitters all in same wave length and transmit a synchronized ...
1
vote
2answers
277 views

Understanding a simple crystal oscillator transmitter circuit

I've recently built this circuit: http://makerf.com/posts/mighty_simple_shortwave_transmitter It works on the desired frequency as you can see from this video : ...
0
votes
0answers
47 views

One Transmitter for multiple recievers

I need to track case pans at work, I would like to do so by using cheap 433Mhz receivers. My problem is we have up to six hundred case pans in the building at any given time. Will I be able to use one ...
0
votes
2answers
513 views

What technique can I use to focus a Bluetooth 4 transmission (or at least shield it)?

I'm actually trying to focus an iBeacon that uses Bluetooth 4.0 LE. These transmit in the ISM band from 2.4 to 2.485 GHz. Normally these things radiate in a spherical, or half spherical pattern, but ...
-1
votes
1answer
186 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, ...
0
votes
4answers
389 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 ...
1
vote
2answers
51 views

What are the trade-offs of transmission bands?

If I were designing an RF circuit how do I determine what band the circuit should operate on? What are the trade offs? and why is the higher the frequency the lower range? It is quite un-intuitive for ...
-1
votes
2answers
179 views

Questions about FM receivers and transmitters?

I have a test tommorrow on phase lock loops, AM/FM receivers along with several other topics. I need to understand this topic clearly before I take the exam to advance to the next schooling in the ...
10
votes
2answers
646 views

How does the plastic-tube inductor in this wireless transmitter work?

This single layer PCB (solder side shown here) is from an old fan remote: The inductor in the plastic tube is not connected physically to any components; however, the two loops of wire surrounding ...
0
votes
2answers
85 views

Peak-to-peak voltage of WRL-10534?

I'm experimenting with the 434 MHz RF Link transmitter (WRL-10534) from SparkFun. I'd like to determine the peak-to-peak voltage of the RF output, but I don't have access to an oscilloscope that can ...
1
vote
1answer
82 views

Wireless transmission power for multiple receivers

I have just started learning about wireless systems and for some reason I'm hung up on what I feel is a fundamental idea. Consider some transmitter-receiver pair with isotropic antennas. The receiver ...
0
votes
1answer
41 views

Replace LED by a Trasmitter

I need a wireless switch with capability to report current state, so I would like to modify a wireless switche like this, by replacing a current state LED by a trasmitter to get the state of current ...
1
vote
2answers
344 views

square wave carrier signal

I am having some trouble to put things together into one picture. Can a modulated carrier wave be a square wave? If yes then How? Because at resonant frequency at the transmitter, the current ...