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Questions tagged [radio]

Consider also the rf tag.

0
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3answers
93 views

Why do carrier waves sound silent on radios?

I was recently reading about and building low-power AM radio transmitters, and read/noticed that when the carrier wave is not yet modulated, the radio receiver goes silent. For example, let's say my ...
-1
votes
1answer
46 views

Long Distance High Speed Wireless Data Transfer

What kind of device can I use to transmit data at a rate of 1MB/min up to a distance of 100 miles? If that's not possible, what's the farthest distance to which I can transmit the data.
1
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2answers
41 views

Determining whether signal meets the 12 dB SINAD voltage

The specification for the sensitivity of a certain radio receiver says: Typically 12dB SINAD NBFM for 0.15uV at 145MHz. If I understand correctly, this means that the received radio wave should have a ...
1
vote
1answer
117 views

Why would a tube radio leave the 6.3V heater tap on the transformer disconnected?

I'm attempting to repair a Clarion C104 tube radio. I started the repair years ago, put it away, and now I'm giving it another attempt. When I started the repair, the transformer (Clarion part no. C80-...
0
votes
1answer
61 views

How frequency is modulated in FM transmitter circuit [duplicate]

I am new to looking at FM transmitter and have a few questions regarding the FM Transmitter circuit below. Please break down your answers as simple as possible as I am not as well versed in circuits ...
0
votes
1answer
47 views

Can we install product above FCC test power level declared in certification report

we have a product which has radio of 1W maximum output power , we have sent product for FCC through party lab, and they certified the product with 18 dbm only. So we get the certificate with only 18 ...
5
votes
6answers
851 views

555 timer FM transmitter

So online, I found this 555 timer FM modulator circuit. But To make this a working FM transmitter, is all I have to do is attach an antenna to the output modulated signal? Or do I have to also have a ...
1
vote
2answers
39 views

RF Design - Antenna Feed-line Parameters

I am implementing a BLE device with a chip antenna. The device has already been impedance matched to 50Ω and is ready to be connected to the feedline and antenna. The antenna datasheet has a ...
3
votes
1answer
149 views

Why can't we divide the electromagnetic spectrum into arbitrarily many radio frequency bands?

I understand there is concern over the limited amount of wireless spectrum available for allocation but am somewhat confused as to why. Couldn't we just divide the electromagnetic spectrum into as ...
0
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0answers
45 views

Single-frequency AM Receiver?

Previously today, I tried to make an extremely simple AM receiver without a tuner. It didn't really work (I'm still trying to work on it), but I also tried to make an AM receiver that is tuned to one ...
0
votes
3answers
155 views

Simple AM receiver schematic?

I've been trying to make an extremely simple AM receiver (without even a tuner), however, it doesn't seem to be working. As shown in my schematic, what I did was connect the antenna wire to the base ...
0
votes
1answer
87 views

Triode Regenerative Receiver Circuit - room for improvement and possible errors

I've designed this radio circuit, it's made to work on the 80m and maybe 40m band. Regen is controlled using a pot in the tickler coil. Tube is ECF82, coil is air cored on a 30mm former. Will it be ...
0
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0answers
70 views

How does this double-tuned antenna work?

I am trying to understand how the attached circuit works, for tuning a transmission/receiver antenna (L1) for double frequency (HF, 500 MHz on the left output and 202 MHz LF right), to be used in ...
5
votes
3answers
1k views

Diode in opposite direction?

Its really bothering me that the diode is shown in the opposite direction here and i don't understand why its been put like that? the input voltage will come from the left side of the circuit then why ...
0
votes
1answer
36 views

Not full-wave signal transmission?

Is it possible to transmit half-wave signals repetitively, like repetitive "north" magnetic fields like going from 0-1 Gauss "north" and repeat however many times per second without going 0-north-0-...
0
votes
0answers
30 views

Why is the length of a cable-type radio-antenna usually determined by c/f regardless of the preceeding pcb trace length?

especially when dealing with low power IoT-devices or these arduino-style radio-modules that don't come with fixed rod-like antennas but rather those cable-type antenna-tails, the length of the ...
5
votes
1answer
110 views

BJT Clapp Oscilator for 3-6MHz

I designed a Clapp VFO to aid in my Ham Radio projects (Non-superhet SSB and CW recievers for 80M and hopefuly 40M). I chose the clapp topology for it's frequency stability. I want it to tune at least ...
2
votes
0answers
55 views

Audio PWM over Radio [closed]

I'm working on a project in which I must send audio over RF such that remote speakers can pick up the signal around a house/apartment. The goal is to broadcast music from a single device somewhere in ...
0
votes
1answer
58 views

Measure voltage of the panel light bulb inside a vintage radio

I'm new to Electronics. I have recently received a vintage radio Pioneer TR-305. I am trying to replace the panel light bulb inside this radio. I opened the radio panel and found the bulb soldered ...
0
votes
0answers
83 views

How does this transmitter work/how to tune it?

I have used a few 433MHz ASK transmitters. They're cheap, readily available, and work reasonably well. Based on this application note from Murata I tried to build my own. I replaced the NE68030 ...
0
votes
2answers
93 views

How does this simple FM slope detector work?

I understand what happens from the diode onwards, it's a rectifying amp and a low pass filter that filters any unwanted frequencies from the carrier, but what is going on in terms of voltage between ...
2
votes
1answer
188 views

How to measure radio signal strength

I am building several types of radio antennas, and I would like to test which is the most effective. I am wondering: What is the best way to measure the strength of the received signal? It is at ~...
0
votes
0answers
32 views

Interference on car bluetooth system

I just did some work on my car audio system and am having some problems with interference. I added a bluetooth receiver and wired it directly to my stereo cd player input. The receiver is powered from ...
0
votes
2answers
79 views

Why don't we use analog remote mics?

All remote microphones sends digital samples over the ether. Why no analog remote microphones? I know that digital signals are less sensitive to noises, but there are several advantages of analog ...
2
votes
2answers
97 views

Why is my radio circuit not functioning correctly?

Ive built this circuit and it hasnt functioned correctly it picks up a humming which im pretty sure it is my power supply Can someone explain why this isnt operating as a radio? and maybe assist me ...
0
votes
0answers
51 views

iPhone headphone out as a signal source for AM modulation circuit

EDIT: I wonder what is the appropriate model for an iPhone/MP3 player audio out? I imagined it as a voltage source that would support whatever current the resistance it’s connected to necessitates. Is ...
0
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0answers
44 views

Antenna selection for CC1101-433 MHz rf

I intend to use these TI CC1101 433 MHz RF modules in one of my project: Wavelength of 433 MHz will be 69 cm. Half wavelength will be 34.5 cm. Vendor is selling two antenna options with the product. ...
0
votes
1answer
50 views

Wiring a bluetooth module into car radio, issue with switching between radio and bluetooth [closed]

I have an old Blaupunkt Radio in my 91 VW golf. I have purchased a Bluetooth module from eBay and I have wired the line out from this into the Left and Right inputs to the amplifier that would ...
0
votes
3answers
132 views

Use 5v Linear Regulator and LDO 3.3V

I am designing a PCB with a STM32 microcontroller, a GPS, DataLogger and X-Bee module. The power supply is a 12V Battery. So in my project I need 5V and 3.3V, at the same time. I don't know if it is ...
0
votes
2answers
106 views

3.5 MHz 2W AM vaccum tube transmitter [closed]

What do you think of my 80m band radio transmitter I designed? Originally I though about using an Armstrong oscillator, due to its simplicity and sine wavyness, but I heard that crystals are better, ...
0
votes
2answers
72 views

Is my radio pulling more current than it should? [closed]

I have an FT-747GX radio that I am using as a RF generator for a plasma cleaning machine. In the operating manual on page 3 it states: I have a power supply connected to this radio which outputs ...
0
votes
1answer
39 views

run ac device on battery [closed]

I recently purchased a radio which unfortunately doesn't have battery option. Its spec is AC 230V - 50/60 Hz and 14 W Is there any way to use my Ni-Mh rechargeable cell battery with this device. ...
0
votes
0answers
26 views

Unwanted buzzing and reduced volume in a basic speaker set

I have the following device, which basically contains 18 songs. we can play the next song by switching the switch on and off. It also has a volume control. Recently it started to buzz a lot and the ...
0
votes
1answer
71 views

EN 300 328 CE radio certification with power limit

We have developed product for Malesia country, where we need local SIRIM certificate. RF module we used in our product is 2.4Ghz wifi mesh, with max 30dbm (1 watt) output power capacity. To get ...
-1
votes
2answers
105 views

op-amp amplifier for small loop antenna

I’m trying to make myself a ferrite core loopstick antenna for a crystal radio project so I’ve pulled the ferrite rod out of an old radio. The rod is about 1.5 inches and I’ve wound my own coil around ...
0
votes
0answers
61 views

High data rate (~1-5 Mpbs) Point to Point Radio

I'm working on a rocket project at my University, and am trying to find a point to point / point to multipoint radio capable of a hopefully 1-5 Mbps data rate between a ground station a directional ...
2
votes
0answers
58 views

2.4GHz RF design losing signal

First time poster here, please excuse holes in the plot. I have a simple wireless design made of an MCU (atmega328p) and an NRF24L01 module, powered through a 3.3V regulator, talking to a similar ...
0
votes
1answer
93 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 ...
-4
votes
1answer
96 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 ...
0
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2answers
212 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 ...
4
votes
1answer
73 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 ...
0
votes
3answers
180 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 ...
0
votes
1answer
83 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. ...
0
votes
2answers
113 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
vote
1answer
64 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 ...
2
votes
1answer
112 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
vote
0answers
61 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 ...
0
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1answer
45 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 ...
1
vote
4answers
139 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
votes
2answers
90 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 ...