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Questions tagged [radio]

Consider also the rf tag.

3
votes
1answer
69 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
48 views

Audio PWM over Radio [on hold]

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
55 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
62 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
56 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
112 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
28 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
76 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
94 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
50 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
votes
0answers
36 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
48 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
116 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
83 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
70 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
38 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
66 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 ...
0
votes
2answers
70 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
57 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
54 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
86 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
79 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
votes
2answers
190 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
67 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
127 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
73 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
81 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
63 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
56 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
votes
1answer
42 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
124 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 ...
0
votes
3answers
132 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 ...
0
votes
1answer
49 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 ...
0
votes
1answer
169 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 ...
0
votes
2answers
155 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 ...
0
votes
2answers
168 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 ...
0
votes
1answer
55 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://...
-2
votes
2answers
106 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)
1
vote
0answers
45 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
vote
1answer
30 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 ...
0
votes
3answers
86 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
votes
1answer
126 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 ...
0
votes
0answers
66 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 ...
0
votes
1answer
63 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 ...
0
votes
1answer
101 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
vote
1answer
38 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 ...
0
votes
0answers
24 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 ...