Questions tagged [radio]
Consider also the rf tag.
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Low Duty Cycle (LDC) Mode Issues on RF Transceiver
I am experimenting with Low Duty Cycle Mode (periodical sleep and active state transitions to reduce average power consumption) on the SPSGRF-915 RF Transceiver, based on the SPIRIT1 RF Module, which ...
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2answers
152 views
Foxhole radio not working
I tried building a foxhole radio but it didn't work. My razor blade is blued and the antenna is long enough. I don't think my speaker is the problem because I hooked up a voltmeter to it and it showed ...
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2answers
62 views
Use opamp for demodulation and amplification
For small frequencies (20-20000Hz) the opamp has output more than -3dB
If we make a low frequency AM receiver , can we use an opamp for demodulation instead of a diode and for amplifications instead ...
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4answers
121 views
Why do we ground radios? [closed]
Why do we ground radios? As far as I know an antenna is an open circuit...
So we just need to put and filter to remove noise and we are ready. However in most schematics I see the antenna is grounded. ...
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1answer
73 views
Figuring out what this circuit does
I need to understand this circuit (at least to a basic point). I know it's supposed to be a radio but I need to break into stages in my head to get what's happening. I am going to try to describe it ...
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21 views
What will be the simple SPI sequence to transmit packet with cc1101
I'm trying to mimic behavior of my weather sensor with esphome and cc1101.
rtl_433 detects ...
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2answers
102 views
Very short range indoor RF transmitter - receiver circuits
I am learning RF electronics and I have the desire to start building real radio circuits with discrete components. So far I have just played with local oscillators (of course, without power ...
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1answer
62 views
Does satellite radio use AM or FM or both? [closed]
Somehow, I cannot find an answer anywhere... I am guessing both...
Several actual satellites had FM in their names, so perhaps that is a clue, but I want to know for sure...
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3answers
142 views
How far can radio signal be transmitted through a straight steel pipe?
We are needing to transmit data between a robot that will be traversing a pipe, and a base station located at the end of the pipe. The pipe is about 2 feet in diameter, made of steel, and is ...
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41 views
RF transformers in first, second and third IF stages, how and why are they different?
Many websites about RF transformers talk about IF transformers to be implemented in first (green slug), second and third (brown, black or orange slug) 10.7 MHz IF stages. Other than this, I don't see ...
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2answers
77 views
AM radio antenna optimization
I am an RF noob and am trying to understand if optimizing an AM crystal radio antenna (maximizing the signal transmission from the antenna to the LC tank) is practical, or even makes sense. Here is a ...
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1answer
58 views
Help recognizing components and parts of this radio telescope [closed]
I stumbled upon this video, where someone is showcasing a radio telescope that detects wifi frequencies and renders them as picture.
There are three parts, and the one above is just the 3rd part (last ...
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2answers
48 views
Radio Waves: Spark gaps vs general wireless radio antennas?
I was recently told by a friend who teaches college physics that "in reality radio waves are only generated when an electric current is made to move violently through a conductor". He went ...
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1answer
72 views
Did I buy a broken RF module? [closed]
I am having trouble with a RF relay module that I bought off eBay, which I am using to control a 30A automotive relay to turn a 12V 20A trolling motor on/off. I’ve attached my circuit diagram below. ...
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2answers
69 views
Radio Waves propagation (Intuitive Understanding of Wave propagation)
I have few similar questions regarding Radio waves communication particularly FM and AM type of Radio wave communication. Please bear with the naivety of the questions.
Questions:
Radio waves in FM ...
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2answers
175 views
Why do AM radio stations have secondary frequencies?
First thing I'm sorry if this question sounds too much beginner-ish. I don't major in electrical engineering so I may lack the basic knowledge.
I have been noticing that, while tuning my AM radio, ...
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36 views
Typical half-wave dipole antenna parameters
From my bachelors degree, I have learnt the fundamental theory behind antennas. One of the main types is the half-wave dipole antenna. We've studied its radiation pattern (isotropic) and how it varies ...
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1answer
60 views
Not getting expected band pass filter response
I am trying to make a LTE signal repeater and trying to filter all other signals except the band 3 (869 - 894 MHz)
This is what I am getting:
This is the circuit:
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2answers
107 views
Why do baseband processors remain on, and communicating with the tower, when the phone is shut down?
I've believed this since 1994 - that if you really want to turn off a cell phone, you need to take the battery out.
But why? What is a good technical reason to keep spending battery charge and ...
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4answers
134 views
How can i make a frequency dependent switch?
Is it possible to make a circuit/switch that turns a relay ON whenever there is a certain RF frequency applied and keeps it OFF for all other frequencies.
The RF signal should not carry any ...
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2answers
73 views
Increasing range of FM transmitter
What things impact to range of FM signal? If I increse length of antenna would signal range increase?
I would like to increase the signal range of this project. Is that possible? Do I need more power ...
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3answers
94 views
How does the LM386 work?
I am not an electrical engineer, but I am curious enough and my mind tells me to make a radio circuit.
Now I am into it, so to make one, I need some components, but before that so that I can be a ...
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1answer
73 views
Which wire is best for solenoids [closed]
I am not an engineer but I want to make a small radio circuit. Which wire would be good for its coil.
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Why does radio reception consume so much energy?
On low-power radios, the current consumption for reception is similar to the consumption for transmission. For example, the Texas Instruments CC2652 System-on-Chip datasheet claims these values:
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2answers
109 views
Why don’t radio waves interfere with each other like other waves? [closed]
I know this question has been asked before, but I still don’t completely understand. I understand that different stations are given different frequencies, but waves are able to interfere with each ...
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1answer
90 views
Can I replace a 101 ceramic capacitor with a close value one?
I'm kind of new to electronics and sorry if this is a bad question.
I am trying to repair my father's old radio transmitter and I noticed that the PTT won't pick up your voice. I opened it up and ...
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2answers
74 views
How to preserve signal power in a splitter?
I have a double Yagi antenna setup that I used successfully in the past, with both antenna connected directly to a 4G mobile broadband WiFi router, achieving 50-80 Mbps. The antenna have different ...
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2answers
90 views
If antennae work best at full, half or quarter wavelengths, why don't received signals at 1, 1/2 and 1/4 wavelengths interfere with each other?
How does a simple radio receiver-antenna differentiate between incoming wavelengths that are the same wavelength as the antenna, one-half and one-quarter?
Or would I just hear static unless I have a ...
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2answers
104 views
How, exactly, does the 'input signal' wave(s) modify the carrier-wave of a radio signal? [closed]
I cannot find a simple (or really, not-so-simple) explanation of how mixing the high-frequency carrier wave with the lower-frequency input signal works...
Is it entirely due to constructive and ...
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2answers
65 views
Calculating capacitor capacitance between collector and emitter in radio circuits
In many radio transmitters and receivers there is a capacitor between emitter and collector. As shown in this answer this capacitor gives positive feedback to prevent decay. My question is that, how ...
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8answers
6k views
Why don't we use lenses for RF?
Radio waves are a class of electromagnetic waves.
Light also is a class of electromagnetic waves.
By shaping a material in which the speed of light changes, we can bend the propagation direction of ...
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2answers
72 views
Dipole antenna circuit diagram
I have this circuit :
simulate this circuit – Schematic created using CircuitLab
I am trying to build a radio and I need to build a band pass filter . How do I do that?
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2answers
135 views
Does it looks like a bandpass matching network?
I am trying to understand this receiver and figure out what does this L-C network is.
I read about matching networks and found this example, I am curious if it is the same thing. is it?
In the ...
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1answer
59 views
Characersitics of a traveling wave on a half wave dipole antenna
For a center fed dipole antenna when operated at resonance, the AC electric potential applied at the feed point results in traveling waves of AC current which emanate from the feed point out towards ...
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72 views
Short range FM transmitter
I made this FM transmitter from this video (https://youtu.be/joFourugXvs) but it has a very short range (30 cm). Where's my mistake?
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47 views
How does current flow in unbalanced antennas?
I have been researching and learning more about antennas recently however I am a bit stuck on understanding how balanced and unbalanced lines / antennas function.
My understanding is that a balanced ...
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27 views
Filtering Options for an RTL-SDR (DSP and Analog routes)
I have several related questions regarding filtering for an RTL-SDR radio. It's readily swamped by the very, very strong AM and FM radio stations local to me. So much so that your basic passive RC ...
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41 views
Design spec for faraday cage
I need to build a faraday cage to shield from the following source: 8 Watt, 14 MHz. The signal is AM modulated
I want to build an metal box enclosing the source. I want it to shield the signal so that ...
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2answers
73 views
Sensor data transmission without using a microcontroller?
What is the most traditional approach to getting sensor data onto a radio from an embedded device pcb that doesn’t utilize a microcontroller?
Up until now, we’ve been utilizing a convenient firmware ...
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Labeling requirements for equipment using off-the-shelf 900 MHz ISM radio
Can anyone tell me or point me to an authoritative reference as to what external labeling is required for an industrial product that uses an off-the-shelf 900 MHz ISM band radio?
I understand that ...
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1answer
51 views
Strange result when simulating RF low pass filter with Pspice
I'm trying to simulate a RF low pass filter in Pspice. The result don't match with my calculations and a filter simulator I found online.
Does anyone know what I'm doing wrong in Pspice?
My ...
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How to correctly document wireless network choice for a project?
Disclaimer: I have limited wireless knowledge at the moment, I'm currently following the Certified Wireless Network Administrator study guide.
I'm working on an RC car and have the following network ...
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1answer
20 views
Can I replace the 433mhz modules on my homemade remote controller with a nrf24 transreciever
I built a simple 4 channel 433mhz transmitter and reciever because I can't afford a remote controller, the range is limited to 3 feet and nrf24 transreciever have longer range, so my question is can I ...
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2answers
29 views
A question about antenna gain and signal property
I have an antenna with a somewhat constant gain "X dBi (theta, phi)" in the frequency range of interest.
With this antenna we receive a radio signal with an amplitude of "Y Volt (t)".
The signal is ...
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47 views
How many periods of an electromagnetic signal are required to be detectable?
Lets say you want a receiver circuit to light up an LED when it receives a radio wave pulse.
How many periods must the emitted pulse last to generate enough electric current to be detectable and ...
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1answer
71 views
Low cost swarm positioning
I'm looking for a way to make a swarm of sensors know their position using low cost, low power system (ie ESP32.)
Requirement:
low cost per device
low power use on devices
1m accuracy is enough
2D ...
0
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1answer
45 views
How to do via fencing of an RF trace with a 5V front copper plane and a GND back copper plane?
Background
I am a building a board to send RTTY via a Radiometrix NTX2B as part of my final year High Altitude Balloon (HAB) project. I have just created a PCB which I uploaded to JLCPCB for ...
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1answer
67 views
Collpits FM Receiver
I saw this simple schematic for an FM receiver:
https://www.mikroe.com/ebooks/radio-receivers-from-crystal-set-to-stereo/the-simplest-fm-receiver
Moreover, I saw some videos online where people have ...
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3answers
123 views
How to demonstrate mathematically the conditions of reflection in transmission line?
We are all taught about transmission lines and its associates -- characteristic impedance, reflection, standing wave, etc. It is well known what happens when a transmission line is terminated with ...
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How would I calculate the frequency range of this FM radio?
https://abra-electronics.com/index.php?dispatch=attachments.getfile&attachment_id=599
Here are more clear images of the circuit and it’s diagram
Any contribution to how this radio works ...
