Questions tagged [radio]

Consider also the rf tag.

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38
votes
3answers
5k views

Why do IR remotes influence AM radios?

When I put my IR remote near any AM radio and push any button on the remote, I can hear a sound from the radio speaker (like beeping). This phenomenon is very weird for me because the radio has no IR ...
6
votes
1answer
920 views

Discrete component FM radio receiver circuit - explanation needed

I have built an FM radio receiver from a kit. I'm very happy with the results! It is the Sinclair Micro FM. My goal is to learn about discrete electronics (NO IC's.) The radio works great, but I ...
-1
votes
1answer
75 views

Tech help with story: Will my radio signal be blocked by a mountain? [closed]

Hoping I can get some help with a technology question for my novel. My protagonist is being pursued, and they have put a tracker in his arm he cannot remove, lest it blow up and kill him. Pretty ...
0
votes
0answers
88 views

What RF frequency can I freely use without a government's permission legally?

So I want to create a transmitter that sends digital signals that have 30 kilometres of range but in my country. Radio transmission without authorisation is only allowed upto 50 metres. I researched ...
2
votes
1answer
160 views

What modulation is this? [closed]

I'm currently learning about signal modulation and fail to figure out the modulation of this signal - maybe someone can help me with it? The software is GNURadio and the device capturing the signal ...
1
vote
1answer
34 views

Would multiple radio repeaters experience feedback or interference from eachother?

I'm creating some sensors that repeat each others' audio feeds over radio in a point-to-point fashion in order to listen much like a distributed baby monitor. Each sensor has a circuit for a repeater ...
2
votes
1answer
182 views

Gain of a Dual Gate MOSFET

simulate this circuit – Schematic created using CircuitLab This is the schematic of the circuit but tried to find the gain of this circuit, assuming 50 % of the Duty Cycle for the LO, and M2 ...
3
votes
1answer
1k views

Can someone explain how this Ratio detector circuit works?

I understand how a Foster Seeley discriminator works, but in this Ratio detector, which is a modified version of the former, I don't understand the purpose of having three transformer windings, or ...
0
votes
0answers
64 views

How to measure noise on an antenna in system

I am working on an antenna based RF receiver (AM/FM radio) that appears to be picking up interference from other parts of the circuit. I want to view the noise spectrum, but the receiver chip doesn't ...
0
votes
0answers
46 views

FCC EIRP test results different than other countries

We have an issue with regulatory testing where our lab reported EIRP varies significantly between separate labs who have tested for FCC and another country. The test methods are quite different. The ...
0
votes
2answers
183 views

Is a coil FM transmitter frequency affected by my body static?

I've built this coil FM transmitter following these guides which are essentially the same: https://maker.pro/custom/tutorial/how-to-make-an-fm-transmitter https://www.instructables.com/id/The-...
0
votes
3answers
143 views

How does a crystal radio headset act as a lowpass filter to remove the carrier wave.?

I saw a similar question " How can a diode act as a detector in a crystal receiver" but one of the comments said "after the diode splits the wave form to the top half ...the carrier must still be ...
1
vote
4answers
339 views

How can I record RF?

For audio I can use just sound card, plus OS api to record any signal from 20 hz (below that's blocked via capacitor) to 96khz(that's half of max samplerate). But what if I just want to go higher? As ...
6
votes
2answers
528 views

What does the wifi amplifier exactly amplify?

The question is not exactly about the wifi, but on how does this operate in full duplex, in principle? As an practical example, lets take some commercial amplifier. As we can see from the picture, it ...
2
votes
2answers
463 views

AM radio wave LED indicator

I recently learned about simple AM transmitters and receivers. Now, I'm trying to apply this and expand my understanding by trying to create an AM radio wave powered LED. I'm a very beginner ...
0
votes
3answers
233 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
302 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
vote
2answers
72 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
227 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
95 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
50 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
4k 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
71 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
167 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
votes
0answers
65 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
403 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
406 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 ...
5
votes
3answers
2k 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
39 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
36 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
256 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 ...
3
votes
0answers
156 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
123 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
494 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
1k 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 ...
3
votes
1answer
1k 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
2answers
95 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
135 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
155 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
105 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
947 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
372 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
133 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
151 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
31 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
119 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
352 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 ...
3
votes
0answers
83 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
138 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
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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