Questions tagged [radio]

Consider also the rf tag.

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How to convert piezo electric signals into transmitted radio signals? [closed]

I want to create a device that transmits impacts measured with piezo elements into radio waves or another type of signal that can be received from close proximity (40 meters.) I have zero experience, ...
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Design a simple x-band radar receiver [closed]

I need to detect X-band radar signals in the range of 9.3-9.5 GHz and make a map of the signals. Do you know of some simple circuits to detect this kind of signals? Thanks
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What is the appropriate name for a parabolic antenna with a "center mounted feed"?

How would a parabolic antenna with a "center mounted feed" be called? Below are some images which illustrate the type of parabolic antenna I'm referring to. According to wikipedia these are ...
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Longwave Radio Receiver, Non-SDR Version

It is my understanding that radio receiver designs change drastically once you get into the sub-MHz range (superhet doesn't seem to make a whole lot of sense at this point). I seem to be leaning into ...
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4 votes
3 answers
481 views

DVB reception: Why do I need to add a coaxial cable to my installation to improve SNR of the signal?

I have the following installation: Dipole antenna <------> Coaxial cable (3 m) <-----> DVB receiver If I connect my dipole antenna directly to the DVB receiver, removing the coaxial cable (...
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1 answer
68 views

Noise factor in homemade software-defined GPS receiver

I'm building a homemade software-defined GPS receiver. I'm currently at a point where I can acquire and track strong signals but struggle to even detect weak signals. I've ruled out problems with my ...
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2 answers
65 views

Can a LC circuit generate frequencies in the Gigahertz range or higher?

For instance, if you took a bunch of off the shelf capacitors and arranged them in series and a bunch of inductors and arranged them in parallel, could you make the resonant frequency of the LC ...
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Mechanical buzzer heard on AM radio

If I connect this little mechanical buzzer to a 3V supply, then hold my AM radio close to it with the radio tuned so I can't hear any stations, I can hear the buzzer on the radio. If I turn up the ...
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1 vote
2 answers
64 views

Super Low Frequency (SLF) compact receiver

I am looking at options for receiving the 50Hz (UK) mains hum from a nearby substation. The goal is to filter some measurements, so I need to produce pulses in time with the zero crossing (or peak). ...
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Field cancellation of small antennas nearby

For example, two loop antennas in the same plane, but current in them is in anti phase. So that when viewed from afar field cancels out. How can I calculate effect of this cancellation? I expect it to ...
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1 vote
3 answers
125 views

Why is my best placement of a directional antenna so weird?

I moved to an offgrid house with a 3G/4G repeater, with a short, enclosed directional antenna. It was wobbling and poorly mounted on an unstable wood plank at the base of a window, so I decided to ...
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1 answer
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Ideas for charging 12v battery

I’m a 17 year old in high school, and for my class project I’m making a cooler with a car radio, and car speakers built in which is being ran off a 12 V battery. It works just fine but I have people ...
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1 vote
1 answer
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Is there any electrical system simple enough to make yourself which has some kind of useful property like radio communication or basic computation? [closed]

I would like to make some kind of primitive system in the direction of a computer, from scratch. Someone showed me you can use ferromagnets to do some elementary computation; the “states” are the ...
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1 answer
172 views

What exactly is this piece of electronics?

I've come across a component which I have not been able to find on Google. My guess is that it could be a sort of radio controller, since I recognise an antenna and a 27M oscillator. I have included ...
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Buying a variable inductor

I need a variable inductor of about 70 nH. I found one at Mouser. As you can see, it says that its inductance is 70 nH, but when I open the datasheet it says that inductance is from 9 to over 280 nH. ...
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What is this device? (from historical photo)

Anybody know what this might be? It's from an old photo with my grandfather as a teenager who went on to work on radar during the war and later for "His Masters Voice" repairing televisions. ...
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1 answer
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Why does short band (high frequency) radio travel longer than low frequency?

In physics, we are taught that longer wavelength (lower frequency) have a lower attenuation in air, and thus is able to travel longer distances. However, when talking about radio channels, short wave (...
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2 votes
1 answer
86 views

nRF24L01+ Doesn't Receive Packets

I am trying to send data from one MSP430 to another MSP430 using Nordic Semiconductor nRF24L01+ radios, but I am unable to receive transmitted packets. I am able to read from and write to the radio ...
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Best antenna design with the following requirements?

I'm looking for the best antenna design with the following requirements Small Discrete Wideband (LTE and WiFi) Directional High gain (20-25dBi with relatively high transmission power) Could anyone ...
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8 votes
2 answers
2k views

Is AM radio louder the closer you are to the transmitter?

Following on from this question, does the volume of the receiver increase the closer it is to the transmitter because it's receiving more of the radio signal? This question specifically is for a ...
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3 answers
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Problem in the book "Radio Antennas and Propagation"

I came across a problem in an electronics textbook by William Gosling, Radio Antennas and Propagation. I am an undergraduate and I sent this to my lecturer to help solve but unfortunately, her answer ...
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4 votes
1 answer
343 views

What does this capacitor do?

Preface: I am not an EE and just a hobbyist. I designed this FM radio circuit and it works as shown. My Question: When C4 was originally, 1nF, there was no output on C2. Once I experimentally picked a ...
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2 votes
2 answers
56 views

Splitting CB Radio Mic Inputs?

I just purchased my first CB radio and I am looking to split the microphone's output such that it can go to two outputs (the radio itself and custom electronics I plan to design). I'm using the Uniden ...
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2 votes
1 answer
77 views

VHF Amplifier Design

I am an RF enthusiast that wants to learn how to think like an engineer. I am trying to build a FM receiver that consists of a wideband FM amplifier and a slope detector. I have so far created an ...
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0 votes
3 answers
75 views

Can an RC receiver antenna work for an ESP8266?

I will be building a project that uses an ESP8285 based ESP01F board (kind of ESP8266) and I need an antenna for this module. The antenna I need should be very light and thin so I thought of using an ...
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2 answers
67 views

Do RF amplifiers increase range bidirectionally?

I read an article where they set up a incredibly high power, high gain WiFi antenna (https://hackaday.com/2016/10/15/a-lot-of-wifi-power-a-yagi-and-a-snipers-scope/). He uses an RF amplifier in order ...
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1 vote
1 answer
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RF direction finding

Is it possible to build a system of antennas to find the rough direction of a radio frequency emitter such as a WiFi router, a Bluetouth tag, or, a 5G cell tower? I cannot use distant antennas to use ...
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33 votes
1 answer
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How did 455 kHz end up being a commonly used IF (intermediate frequency)?

Of all possible IF frequencies, why did so many consumer radio and amateur HF radio manufacturers (and filter component vendors, etc.) end up converging on 455 kHz as the IF frequency, from the vacuum ...
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9 votes
8 answers
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How can the same radio signal be received by 100s of receivers without any loss in it?

In power supply, each house connected to the grid consumes a certain amount of power which leaves less power to be consumed for the rest of the houses. Similar to that, when a radio station broadcasts ...
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RFM69HCW Digital IO connection setup

I'm working to setup an RFM69HCW transceiver with an ARM microcontroller. I've read over the datasheet for the RFM69HCW and I see that DIO0 is the interrupt signal, so I've broken that one out, but ...
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2 votes
0 answers
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Esp32 rf design review

Preamble: this is the first time I'm working in rf circuit design, I went simple and I hope I didn't make any silly mistakes, but I still have some doubts. I am currently designing a garden programmer ...
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0 votes
2 answers
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Why can't WiFi hardware be used to receive radio stations?

Special hardware is needed to receive radio waves in different frequencies i.e a RTL-SDR. My question is why can't the WiFi hardware get also used to pick up radio ...
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1 vote
2 answers
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Does the antenna design equate to the range?

There are a ton of different antennas out there, here specifically I'm talking about directional antennas. Options include Yagi-Udas, parabolic, LDAP, etc. antennas. All of these have somewhat of a ...
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2 answers
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Does DC voltage affect the frequency?

Does DC voltage supplied to the tank circuit impact its frequency? Imagine that varactor is just a normal fixed capacitor, but for some reason there's voltage supplied between the capacitors. Ignore ...
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Estimating the range of an antenna and determining what the best option is?

I'm very new to radio communication so I apologize for the lack of knowledge about this subject. That being said, I'm looking for a directional antenna imagine a situation as follows, I'm in a rural ...
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1 vote
1 answer
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Part identification / replacement: RF PA

Story I recently aquired (second-hand) a Yaesu FT-252 handheld in unknown condition. It turned out to mostly work, but was found very weak. Investigating it in the HAM club we found that the PA IC is ...
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0 votes
1 answer
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Can someone please explain the antenna and gang capacitor of this AM superheterodyne receiver?

This is about an Elenco AM/FM superheterodyne radio receiver. I have noticed a similar post (Can somebody please explain the antenna and mixer stage of this AM superheterodyne receiver?), but still ...
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6 votes
1 answer
1k views

2.4GHz sender cause 433MHz receiver jammed, vice versa

I have a 433MHz receiver placed near a 2.4GHz sender, and they have about a 20cm gap. When 2.4G is actively sending, the 433M receiver can't hear anything from the 433M sender (433M receiver been ...
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0 votes
1 answer
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Is this radio receiver/transmitter plausible?

Previously I have created a simple radio receiver using the schematic below (based off a crystal radio), and I was wondering if the modified circuit which is also below would work for a simple morse-...
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1 vote
2 answers
152 views

Advantages of I and Q receiver over "real" signals receivers

I wanted to know better which are the main advantages of using an I and Q receiver like that: rather than a simple demodulator whose output is a real signal like that: Here some advangages are ...
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-2 votes
1 answer
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Audio over radio in neighbourhood, possible and legal? [closed]

In my neighbourhood there are three five-year-old friends (including my kid) that live within a radius of 450m of each other. I had an idea that it would be fun if they could have some kind of push-to-...
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0 votes
1 answer
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A simple DIY example of how bit sequence is converted into corresponding radio wave sequence, and vice versa

I'm a beginner in electronics, have during a 1/4th semester introductory course in electronics the past 2 months covered quite a lot, and everything was presented from simplest "DIY" ...
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0 answers
57 views

When multiple cognitive radios transmit simultaneously

Cognitive radio nodes sense the spectrum and start their transmission opportunistically when the spectrum is found to be vacant. The question arises what if two or more nodes find the spectrum to be ...
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1 answer
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Adding a DC Power Adapter Socket to Sony AM/FM Radio

A friend has asked me to do a mod on their basic Sony AM/FM Radio (Model ICF306). It's 3V based but only accepts batteries. I thought about opening it up and soldering a 5.5mm Socket across the +/- ...
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0 votes
1 answer
92 views

Radio receiver for car keys

I'm not sure if this question is ok to ask here but I'm hopeless in finding sufficient hardware for it to be done. I have two pairs of keys to the car and one of them stopped working so I want to ...
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0 votes
2 answers
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How to find the output power of antenna including distance?

I have a PCB and antenna (1) attached to it at the output. Now I would like to measure the output power of the antenna (1) using antenna (2) which is at a distance of D. I have the readings of the ...
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-1 votes
1 answer
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How do these LC circuits work?

The Very Short Version A.K.A tl;dr; A transistor is needed to make tank circuits continually run. How does the transistor make tank circuit do this? Is it adding to the electric field of the capacitor ...
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1 vote
1 answer
91 views

Simple analog AM radio generating noise throughout circuit [closed]

I'm building a simple AM radio circuit for one of my classes. It works insofar as that anywhere from 400 Hz - 4 kHz we get a nice AM radioey tone. But when the outputs are connected to an oscilloscope,...
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1 answer
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5 V radio on 12 V battery [duplicate]

I am working on a powerbox project (12 V): charging a cell phone, lights, banana plugs and a small radio. 12 V is somewhat straightforward for me. The radio (https://rb.gy/e6ngmo) works with 3 V to 5 ...
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1 answer
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My AM radio receiver using TA7642 IC is not working

A very simple question I’m sure but I’m struggling with making an AM radio using the TA7642 AM radio IC. I’ve looped maybe 200 coils of 0.25mm enamelled copper wire around a 1cm ferrite rod and made ...
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