Questions tagged [radio]
Consider also the rf tag.
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1answer
63 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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2answers
45 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....
1
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1answer
54 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
83 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:
...
1
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0answers
46 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
32 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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0answers
23 views
Directional HDTV antenna
I bought a cheap directional HDTV antenna, with an amplifier. It's a flat rectangle, like a sheet of paper. It's designed to work with the flat face facing the signal. It works fine. However, it ...
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4answers
103 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 ...
2
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2answers
82 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
114 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
40 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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0answers
48 views
Melted mystery part on old Telemania Jeep Radio
I'm trying to fix an old radio. It looks like a part melted on the circuit board. Any idea what is is/how to figure out what it is/where to get a schematic? The radio was manufactured in 1998.
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1answer
91 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
153 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
156 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
51 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
100 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
41 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
29 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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0answers
52 views
Locate objects within a bus using RF signals
I am designing a tracking system for transportation services (mainly buses for now). There will be a host device(s) on the bus and small tags on the objects needed to be tracked. I need to know in ...
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3answers
81 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? ...
0
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1answer
120 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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0answers
40 views
Derive required carrier to noise or signal to noise from receiver sensitivity on FM receiver
Can I extrapolate the required C/N based on reported receiver sensitivity?
I'm plotting coverage for a repeated radio system for handheld radios. The system is analog, FM narrow band. I've ...
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1answer
58 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
71 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 ...
1
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1answer
36 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
17 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 ...
4
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2answers
188 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 ...
0
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1answer
64 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 ...
0
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1answer
48 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
118 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
206 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
19 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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0answers
58 views
Crystal Radio Help
Me and my uncle have been working on making a crystal radio for the last few days and have had no success. We have used multiple designs but none of them seem to work. This is the one we've been ...
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2answers
88 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
65 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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0answers
41 views
Will 2 nearby crystal radios affect each other's strength?
I'm working on a project which involves 2 nearby crystal radios. Their cases almost touch each other. They are tuned at different frequencies. I was wondering if they would affect each other's ...
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1answer
53 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
184 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
475 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
149 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
59 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
354 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
79 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
75 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 ...
0
votes
1answer
205 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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0answers
90 views
Why do I hear static when the radio is turned off?
I've been keeping around and old radio which I use every now and then (last time was about two months ago). One day it just started making white noise. I checked if I might have left it turned on, but ...
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2answers
89 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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0answers
47 views
Discrepancies in calculating the edge impedance (resonant input impedance) of a basic Microstrip Patch Antenna
Before I jump to my problem, here is a bit of context.
I have been working on a MATLAB code that can help me calculate all the required parameters for a patch antenna. These parameters are for ...
1
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1answer
78 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 ...
