Questions tagged [radio]

Consider also the rf tag.

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1answer
139 views

How to increase range of AM radio waves? [closed]

As a personal project, I made a very simple AM transmitter with an idea from an online tutorial, using a 1 MHz crystal oscillator (plus power source, antenna, breadboard, etc.). However, when using ...
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1answer
233 views

Are headphones with EMF measurement of 10,000 milligauss harmful to me?

I used a EMF detector app on my phone and measured the EMF output on my wired headphones. It measured around 10,000 milligauss on one part of both ear cups. Since wearing these headphones on my head ...
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2answers
367 views

Explain this circuit

I know this circuit is an oscillator circuit and it senses another signal of same frequency, but I don't understand the calculation behind it, and the reason for emitter inductor, 3.9k collector ...
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1answer
88 views

What kind of modulation technique and carrier frequency is used for interplanetary communication such as between the Earth and Mars? [closed]

I have just come across this wind sound coming from pressure sensor of Insight lander which is in Mars at the moment. I know basically that AM, FM, PSK, FSK ect. all have disadvantages and advantages ...
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3answers
479 views

Why does antenna tuner in crystal radio use capacitor and an inductor?

I know that antennas can be capacitive or inductive depending on the relation of antenna length to the \$\lambda\$. I know that crystal radios use both antenna and capacitor for tuning and I don't ...
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2answers
907 views

Can a speaker be driven by a DC signal?

I’ve always been under the impression that speakers require an AC signal. The reason being that positive and negative current are required for the electromagnet to properly vibrate the diaphragm. ...
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3answers
677 views

Speaker for crystal radio rather than sensitive piezoelectric speaker Crystal radio

I am a science student of grade 8 and researching and learning about radio waves. I am currently trying to make a crystal radio. The problem I am facing is the speaker I have to use for the project....
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1answer
74 views

Other than direct radiation, how can RF interference transfer between stacked PCBs?

I have VHF aviation radio consisting of 3 boards stacked upon each other: digital, receiver and transmitter, the digital is on ‘top’ with receiver in the middle, there is thick shielding between the ...
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1answer
117 views

Amateur radio practice exam question

The question is as follows: An interfering signal from a transmitter is found to have a frequency of 57 MHz (TV Channel 2 is 54 - 60 MHz). This signal could be the: And the options are as follows: ...
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0answers
82 views

Electro magnetic interference with Arduino Uno and a portable radio

I'm surprised when I'm working with Arduino Uno, by just sitting beside a portable radio, like when I was powered on both Arduino & Radio and when they are close to each other I got some noise ...
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1answer
216 views

Receiver Antenna Gain

How is gain defined for a receiver antenna? If we look at a radiating antenna, there is a Pin, and the gain in a particular direction would be the radiation intensity Ur, divided by the radiation ...
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4answers
262 views

What happens if the frequency of the receiver osc does not match (exactly) the carrier frequency?

I thinking about FM and AM. Theoretically the carrier frequency is perfectly match the demodulation frequency. But what happens if there is a mismatch? I think using AM the frequency of the base-band ...
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2answers
92 views

Antenna Design Procedures

I live in a residential area and I want to test and design an antenna in my garage. I plan on using my signal generator as the power supply and a RTL - RDS dongle connected to my computer as the ...
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3answers
335 views

Voltage gradient across an antenna (and how it drives an AM radio)

Edit: I was interested how is voltage gap maintained across an antenna. It seemed to me that an antenna might be like a wire where if there's a voltage at the top, the same voltage would be at the ...
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1answer
68 views

Radio activated on/off switch

TL;DR: I want to know if there is anything, That on which when a radio frequency falls, and it turns on an LED. Basically an on off switch but controlled when radio waves hit it. What I hope to ...
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1answer
648 views

What does a TV receiver circuit look like? [closed]

I found a few circuits for TV transmitters, but no receivers. I've looked at other simpler RF transmitters and receiver, but it's not obvious to me how to reverse the circuit that I have. I want ...
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2answers
181 views

Name of an electronic component

Can anybody kindly tell me what this electronic component in the picture is called? I've seen this component in: Mobile phone circuit WiMax modem circuit GSM Module circuit I tried but was unable ...
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2answers
198 views

Can I use more than one antenna with a radio module (say rfm69) and switch between those antennas electronically, say by a transistor

I need to know the approximate direction of the radio signal coming to my module, and I have to use very simple hardware and software for this. (Just a microcontroller and one module) What came up ...
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1answer
166 views

How does adding more coils to an AM tuner coil allow it to tune Shortwave?

I have seen several tutorials about how to turn an AM radio into a Shortwave radio. They add more coils to the inductor (is that the correct name for the tuning coil?). Here is one example, https://...
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2answers
119 views

Why FM has larger range than cellular network [closed]

I can receive FM signal about 50km away from the transmitting station but I lose signal from cell towers in about few km (1-3km)
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0answers
52 views

Active phased antenna array for Wi-Fi efficiency compared to a directional antenna?

I'm interested in mesh networking of poorly controllable autonomous aerial vehicles (like blimps), so i wonder whether it is viable to use a phased antenna array versus a few traditional directional ...
1
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1answer
31 views

Radio Telescope Rx/Tx resolution

Very simple question. If (say) a 65m radiotelescope obeserving at 5cm (6GHz) has a resolution of about 1mRad, if it becomes a transmitter at that frequency does it radiate a beam of the same ...
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3answers
103 views

Is a modern radio wave broadcasting station a very fast spark gap transmitter?

In a spark gap transmitter, is that a "real" radio wave that is produced? I know you can hear it on an AM radio, if you are close to the gap, but is it a radio wave the same as from a radio station? ...
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1answer
140 views

UHF transmitter Range for 50 W

Very curious to know the range of 50 W transmitter of UHF range in nautical miles? The antenna used is 1/4 wave antenna of Jaybeam company. Can someone tell the exact formulation to find out the ...
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1answer
66 views

Understanding the Practical Application of a Simple Antenna made from Coax

I am here today to gain a deeper understanding of the fundamentals of using antennas in RC applications. I am trying to understand what exactly is going on with a particular 2.4GHz receiver a picture ...
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1answer
254 views

EHF RF Transmitter and Receiver

We are working on a blood glucose meter that will measure BG readings through radio waves with a frequency between 60-70 GHz. That range is necessary to allow penetration through the tissue and we ...
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1answer
46 views

True near field distance for a short monopole antenna

Antenna properties: Height x Diameter = 3.3 inches x 1.4 inches Test Frequency: 900 MHz (Wavelength = 33 cm or 13 inches) I see some conflicting formulas to calculate the near field distance for ...
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0answers
55 views

HM-TRP radio module works at 56K data speed but only in delayed chunks

I created the following setup: I created one circuit in which the PC connects to an HM-TRP radio module via a max232 DIP IC. This circuit for the test is the master to all devices and sends a 16 byte ...
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2answers
202 views

Is a regulator necessary?

Sorry for the provocative subject line. I was looking at using one of those integrated ESP32 + SX1276 + SSD1306 boards (there are a few that have popped up) in a battery powered application. I would ...
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1answer
1k views

RF Combiner Losses

I'm having a hard time understanding what is actually achievable with an RF combiner. Let's consider this scenario, here port 1 of the RF combiner has a sinusoid at f1=100Hz and port 2 has a sinusoid ...
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1answer
92 views

How to test an RF crystal oscillator performance integrated into a Cellular radio?

I have a couple of reference designs with 2 different crystal oscillators integrated into it. These are cellular radio and can generate standard LTE QAM signals out of it. But I do not have access to ...
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3answers
2k views

Can I apply gorrila glue on to a AAA battery to attach a wire to it? [closed]

I am repairing a old CB radio I got at a yard sale and I'm powering it with 2 AAAs and a 9 volt. I have to attach a wire to all of the ports, and tape isn't very effective. I'm wondering if it it safe ...
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3answers
521 views

Radio Transmitter Circuit [closed]

I have seen previous similar answers about radio transmission, but looking at the following scheme I am not sure about the role C3 plays in the circuit. I guess it is needed to remove the DC signal ...
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1answer
56 views

Regulated power for radio module HM-TRP. Is config correct?

I'm trying to figure out how to make a nice power supply to the radio module HM-TRP. I heard that running certain voltage regulators with capacitors having high ESR values is a bad idea and will ...
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2answers
612 views

Question on Use of Y2 Saftey Capacitor in AA5 Style Tube Radio

In a radio I am restoring, there is a 0.1 uF capacitor between B- and chassis, designated as C12. My thought process is that if this capacitor were to fail, I would not want B- shorted to chassis as ...
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3answers
110 views

Use existing WiFi hardware as an RF receiver? [closed]

I have seen mine & many others' (Android) devices nowadays have WiFi hardware capable of connecting with 2.4Ghz & 5Ghz APs. Wanted to know if I could tweak the WiFi driver in the kernel source ...
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1answer
60 views

Low power local area radio controller chipset [closed]

I have a project where I need to remotely control up to 128 individual relay boards within a maximum 30 meter radius. I need each of these wireless relay controllers to be uniquely addressable to ...
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2answers
216 views

Are IOT wireless network protocol right for high throughput point to point communication?

I am trying to build a "professional" 2 way point to point radio system (like this) to control a RC 1/10 scale car (like this ) using UART, the challenge I am currently facing is finding the right ...
3
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2answers
721 views

Expected peak-to-peak output voltage of satellite LNB

Anyone know what the output voltage of a typical DirecTV LNB might be? I've converted an old dish to be a backyard radio telescope and I'm hoping to record output levels with a USB oscilloscope, as I ...
2
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1answer
381 views

Old Radio Colpitts Oscillator? Or not?

I am a beginner hobbyist form Brasil, posting here for the first time. I am trying to understand the schematic of an old Transglobe radio that my late grandfather gave me. It motivates me to learn ...
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2answers
81 views

Antenna Design for Omnidirectional transmission

I have been working on a custom drone for quite some time now. One thing I have found an issue with is the remote control antenna orientation in relation to the drone. In some directions I will get ...
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2answers
2k views

calculating maximum transmission distance of radio module based on dbm and open air

I own several HM-TRP TTL FSK radio modules, and every time I turn one on, it reports it as being version 2. Anyways I did read the manual and it has a setting for transmitter power as follows: <...
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1answer
95 views

What single feature will enable ultra low latencies for 5G communications? [closed]

there has been a recent buzz around 5G and its ultra low latency use cases. Additionally, some people claim that data rates around 10 Gbps are a feasible scenario if mmWaves are to be used. I was ...
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3answers
82 views

Consistent Radio wave detection timing

Bigger picture: What do I need to do? I need to send a radio signal and have another device receive that and output a voltage pulse, with the time between starting to send the signal and starting to ...
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1answer
616 views

Dip switch or rolling code garage door opener?

I'm a total noob in electronics field and want to begin. (I'm an IT engineer). I'm trying to use my remote garage door opener (868 MHz HF) to create a system with my Raspberry Pi so I can replicate ...
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2answers
179 views

Why do rubber duck antennas have this metal part, while other antennas do not?

If you open up a rubber duck antenna, it usually has a wire inside, plus a crimped on piece of metal, like this: Other antennas, like those on an RC receiver do not have this second metal part: Both ...
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1answer
206 views

Ground Plane for Antenna on Carbon

I'm working on a radio module that is made to transmit from a rocket to a ground station for a homemade project. The airframe is made of carbon, therefore I cannot place the antenna(s) inside the ...
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1answer
93 views

In heterodyn receiver circuits, why is the LO not chosen to match the target frequency?

I'm trying to design a device that detects motion using sonar. I'm basing it on a common superheterodyne receiver like this: Now from what I've read, in radio audio receivers the local oscillator is ...
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0answers
56 views

Why is it difficult to localize shortwave transmissions?

I have read that it is difficult to localize shortwave transmissions, but I don't understand why that is. I know that localizing the bounced transmission is obviously difficult, but when the antenna ...
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1answer
99 views

Radio frequency detection without digital clock [closed]

Is it possible to have a circuit that does something (fires a pulse, turns on a voltage, whatever) when it detects a radio signal at a specific frequency? One crucial point is that it should do this ...

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