Questions tagged [radio]

Consider also the rf tag.

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0answers
12 views

How do i find the FNBW of a main lobe using a diagram?

Looking at the graph below, i can see that HPBW of the main lobe is around 45 degrees, but when it comes to identifying the FNBW i have trouble understanding it. Reading various articles online i've ...
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1answer
66 views

Watt output of radio station

I was wondering how many watts an AM radio station outputs, and if I can calculate the watts on a tuned antenna by this equation: Where Win = the watts input for the antenna, Wout = the watts output ...
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2answers
106 views

What makes it hard to build a powerful RF transmitter?

I was looking for a powerful RF transmitter lately but I didn't find many. They are low power (< 0.5W) or expensive. I have a little understanding of a regular 433MHz transmitter's schematics. It ...
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4answers
64 views

Negative resistance in a regenerative radio receiver?

Why is an amplifier with a tuned circuit and positive feedback, such as a regenerative radio receiver, said to exhibit or have negative resistance?
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2answers
2k views

Where is the antenna in this remote control board?

This is a PCB of a (radio?) remote control.
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1answer
75 views

Is this a demodulated signal?

1st attempt I have a problem. I built the FM demodulator circuit, but i am not sure if this signal is demodulated. This was my first attempt which following an answer, resulted in a 2nd attempt ...
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1answer
67 views

How does my 802.11 a/b/g/n wireless card determine the modulation to use?

I was thinking yesterday about how the 802.11 a/b/g/n standards all use different modulation schemes, but my wireless card manages to detect frames from networks that may use any of those modulations. ...
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0answers
117 views

Ratio detector FM demodulator

The aim of the exercise is to design a ratio detector FM demodulator circuit. UPDATE: I changed the circuit: This is my transient analysis in output: I found the information about AC analysis and ...
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2answers
38 views

What is the irregular signal at the bottom of this “spectrogram”?

I am reading research papers about LoRa, and I have come across the below figure in this one. The horizontal axis is clearly labeled frequency, but the vertical one isn't. I recognize the chirps in ...
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57 views

How does one choose a resistance for an AM radio antenna receiver tuner?

[![enter image description here][2]][2] I am using some pretty rough, brute force and novice calculations, so if anyone knows a nicer method I am happy to learn. I want to build an AM radio receiver ...
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42 views

TTE low frequency radio transceiver

I'm interested in developing a bespoke through-the-earth (TTE) radio transceiver for a measurement instrument in a limestone cave system. The issue I have is that conventional RF signals cannot ...
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0answers
71 views

'P.V.' marking on 1940's electrolytic capacitors

I am replacing the paper and wax capacitors in a tube radio of 1949 vintage. Puzzled by the initials P.V. where I'd expect to read VAC or VDC. Can anyone explain this puzzling jargon? For some reason ...
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1answer
68 views

Is it true that FPGAs and DSPs are widely used for modulation and demodulation of signals? [closed]

I have to write a thesis about digital communications, and I don't want to write something stupid in it. I also wrote that "most of the digital modulations and signal processing nowadays are done ...
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1answer
45 views

Formula to calculate the isotropic range of a signal

I am wondering, is there a formula to calculate the range of a signal with a given frequency and output power? For example, how do i find the range of a 580khz AM signal on entirely flat terrain with ...
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1answer
28 views

Modern substitute for BF494 or 2n3707 transistors

This question has been asked before, here: https://electronics.stackexchange.com/a/263366/199668 But since it's been almost 5 years since that post, does anyone know any substitutes for the mentioned ...
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0answers
13 views

Split loop cavity or Loop gap cavity

I want to make a code for the power vs wavelength for the split loop cavity resonator. Can someone help me with the python code for the same?
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3answers
102 views

Noisy AES audio signal in studio installation

This is a question about digital audio cables. I know this isn't an audio engineering forum but the question's specific to the physical connections and there's limited info online which I can find ...
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3answers
1k views

Hearing only noise and ticking sound with simple AM radio - The art of electronics

I've tried to build the simple AM radio that is proposed at page 56-The Art of Electronics (3rd). The idea is to tune my radio on a frequency of 657 kHz (I'm sure there's a station at that frequency)....
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1answer
100 views

Do AM radio broadcasters pick frequencies that are picked up as interference on purpose? [closed]

This is not meant to be a political question, rather a historical one, USA based. Every place I have lived, if I have an amplifier with a long enough input wire, I will start picking up AM radio if I ...
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1answer
106 views

Vintage Pocket Radio Transistor Replacement is Oscillating

I have an old pocket radio which uses silicon NPN transistors for the mixer and IF stages. I replaced 2 of the IF transistors and the unit functions, but the new transistors are faster than the old ...
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1answer
85 views

What is the benefit of dual polarization in radio communication?

Why are some PtP antennas and radio units connected by two feed lines -- one for horizontal polarization and one for vertical polarization? I know the difference is in the orientation of the electric ...
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2answers
97 views

FM receiver not picking up any stations

I am trying to make an FM receiver. I have a radio transmitter and it's able to pick up and demodulate the signal from that when the transmitter is beside it, but the problem is when I try and pick up ...
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0answers
29 views

LoRa RSSI value is not accurate

I want to use LoRa (SX1280) to locate devices by RSSI and TDOA. I put two LoRa devices on the table (within one meter,) one for TX one for Rx, and the RSSI values change a lot. Then I power off the TX ...
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34 views

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
170 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
63 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
133 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
75 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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32 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
112 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
87 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
158 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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0answers
45 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
91 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
60 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
51 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
73 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
75 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
178 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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0answers
42 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
62 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
132 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
144 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
169 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
132 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
76 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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4answers
4k views

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
167 views

With so much radio signalling occurring simultaneously (TV, Cellphone, Radio, etc.), how does our atmosphere keep them separated and avoid disruption? [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
130 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
75 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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