Radio Definition and 691 Threads

if i decide to build two relay stations 100 miles apart, what frequency or frequencies should i use to send a radio signal across 100 miles from 1 relay station to the other relay station.

Just wondering if I understand "radio bands" correctly I am not sure I do. Lets say you have a radio band of 10 GHZ to 30 GHZ and another from 10 HERTZ to 30 HERTZ, the information or a song transmitted will sound the same in those two ranges, the only thing that matters is the amplitude or the...

I have some doubts about whether Planck's relation (E=hf) applies to radio waves. This has been bugging me because trying to apply Planck's relation to radio frequency results in some inconsistencies that I've been unable to resolve. BTW, I have no physics training, so please go easy on me...

Homework Statement: I am having difficulty understanding what exactly is happening when radio transmissions are being absorbed by oxygen at 60GHz at the atomic level. Homework Equations: Refraction/reflection, oxygen absorptions/attenuation, frequency I have tried to find the answers online...

I confess that I am unable to understand the technical presentation in this article. I am hoping that someone at PF will be able to respond with a simplified summary about what this article is describing. Quote from Abstract The Galactic Centre contains a supermassive black hole with a mass of...

Time travel teleportation can be achieved in small scale experiment in millisecond. Using a computer byte in radio signals. I look forward for comments.

So I'm trying to put together a Pi Zero mini computer to use for security-oriented applications, for example encrypting/decrypting messages, working with encryption keys, etc. It's cheap, very small and thus easy to carry around. However, I'm not entirely comfortable with the presence of the...

My question is: is the resolving power of an array of radio telescopes a quantum or a classical effect? The increase in resolving power of a single telescope, as aperture size increases, is easy to explain in terms of Heisenberg's uncertainty principle. But when we go an array of telescopes are...

...and so did the Canadian and Indonesion quakes. An Amatuer Radio (Ham) operator runs what he calls an "RF Seismograph" in Vancouver, British Columbia that noted a blackout on 10 meter and above bands and increased noise on 80 meters. Here is the ARRL article with a few more embedded links...

The answer says its 1 meter i don't understand how they arrived at this, The mark scheme suggests that the 50mm is the resolving power or Rayleigh criteria? https://downloads.umutech.net/Physics/Past_Papers/PA05/Astro/MS/physics_u5_astro_ms_jan_2003.pdf

I have found plenty of information about the radio source Hercules A. Its large radio jets are 1.5 million light years long from end to end, the supermassive black hole that produces Hercules A is 3 to 4 billion solar masses, and the black hole exists in the center of galaxy 3C 348. However, I...

I've seen this video: There it is explained that an electromagnetic (here radio) wave has a phase shift if it was radiated in horizontal polarization, but it does not experience the phase shift when it was emitted vertically polarized when it gets reflected on the ground. When reading up on...

A new kind of radio transient: ERBs arXiv:1903.12412v1 [astro-ph.HE] 29 Mar 201 Another fascinating paper by Ali Frolop et al. in yesterdays arXiv: Garth :oldwink:

I am trying to build a radio to transmit morse code. I have built A wien bridge oscillator on a breadboard. I think the wien bridge Oscillator works. How long should The antenna be?

If anybody here has any experience with building a crystal radio, I would appreciate a response. My grandson and I are doing radio projects. This involves basic crystal build using a coil, diode, and resistor. The system is grounded and uses an antenna with no external power and a high...

Hi! Just in case someone is interested in SETI, I made a video about the most promising radio signals detected so far. Here it is: https://www.youtube...h?v=4MxNEfIfQjI Hope you enjoy it! What is the most promising SETI radio signal for you guys? Do you think we will discover an intelligent...

https://www.cbc.ca/news/technology/fast-radio-bursts-1.4969863

Hi, I just finished studying Maxwell's equations. Based on my understanding, when you solve maxwell's equation, you get the wave equation and it simplies to in a charge and current-free region. I understand that these two equations are similar to an equation of a wave in space. What I am...

I didn't see where anyone else had brought this up. From the article: The telescopes are the Murchison Widefield Array (MWA) and the Australian Square Kilometre Array Pathfinder (ASKAP), and they were synchronized to observe the same patch of sky, searching that area for fast radio bursts...

So, I've been really interested in Particle Physics since 6th grade when I did a project on particle accelerators. I understand most of it, except for one thing, the radio frequency cavities which are used for acceleration. I just want to ask, how do the Superconducting Radio Frequency Cavities...

There are many electromagnetic waves. Some of them are visible while other are invisible. Can we see those invisible electromagnetic waves? How Please give with scientific reason.

I would like to be able to triangulate a sound's location based on the inputs of two robotic sensors. I know this involves trigonometry, but I am a little out of practice. I think the practice of triangulation also is useful for radio signals. I would like to create a triangulation algorithm...

Homework Statement P.S.: I'm not sure if it is allowed to ask multi-part questions. Two equally old sisters Alice and Barbara leave Earth simultaneously in opposite directions. The following velocities and distances have been measured in the Earth system. Alice travels with a speed of ##v_A =...

Back when dinosaurs roamed the Earth, every car had a push-button radio like this: You pushed a button and the dial would zoom to the preset location. To set a location, you would manually dial to the right location, then pull the button out, then push it in. I had set my sights on figuring...

The radio would work sometimes if it didn't pushing on the tuning buttons hard or hitting the dash underneath would make it work if it didn't work, this has been that way for 30 years, now it does not come on at all. I always thought it must be broken connection some where. I had applied voltage...

What are the methods to record and Playback Radio programs tuned to FM frequencies ? Is there a way to interface the radio receiver with DVD player or Flash drive or any other media for recording and Playback ? Thanks & Regards, Prashant S Akerkar

Why do radio waves pass through walls while visible light can't? I guess this has something to do wit the wavelength. What I know is that higher wavelength means higher ability of penetration. So why radio waves penetrate obstacles?

So I recently picked up 40 of 10.525 GHz Microwave RADAR transmitters: I opened up one out of curiosity and had something like this (image attached) . I noticed some parts of the PCB aren't even connected to anything. How do the different shapes and sizes of the PCB interact with each-other...

I understand that a radio telescope can be tuned to receive radio waves generated by neutral hydrogen atoms present in galactic gas, for example, within the spirals of the milky way. I think I understand that the incoming radio waves will be a mixture of red- and blue-shifted photons depending...

Hello, i build the radio like they say in the book, and i did everything with VOM(testing with only multimeter), everything was like in book , but when i finish, i switch to am or fm, i just hear high noise :doh:

How do I stop multiple radio frequencies ...Micro, Infra and combined frequencies used in a sweep rotation(?? guessing here) ...from any space. Thank you for any advice you can give. Been traveling. For the record I thought...wearing magnets ?? I have some minimal back ground in RF but am a...

Hi, I was wondering if any of you fine people can help me understand a few things about Howard Armstrong and Harry Houke's superhet radio receiver built in 1924. My fist question is that they used a second harmonic and I don't understand why. Where was the second harmonic used and how did it...

I noticed HF radio waves travel farther and easier when the sun is out rather then during the night. Why?

Does the spark frequency = the interruptor frequency = radio signal frequency. From the sources I have found these frequencies don't seem to match. We use a 9V DC one at school. Many Thanks

I had an idea of building an FM receiver that is powered from the electromagnetic fields generated by power-lines. My question is , how can I make the electromagnetic field receiving antenna? Will a simple copper coil work? If so, can the same coil be used as the RF antenna or will that have to...

Why do GPS need a cesium clock accurate to 10ns? Is this strictly for time keeping or is there some synchronization between satellites?

How exactly do the elements "connect" to each other to make an antenna directional? I see some Yagi's have a reflector but most do not.

For an optical telescope, light pollution is a problem and that's why put ground-based telescopes in remote places where there isn't much light. However, aren't we bombarded by radio waves from satellites for our phones and TVs? How do radio telescopes remove those?

Homework Statement A radio transmitter is located 17.5 km away. The broadcast signals travel at the speed of light (c = 3.00 x 108 m.s-1) through the air towards a radio receiver. Calculate the time it takes the radio signal to travel from the transmitter to the receiver. Homework Equations...

So I printed this antenna with some conductive filament , however the microwaves seems to be going between the layers of the plastic. I surrounded it with Aluminum and still leaking, what can I do to fix it? Can conductive silver paint work?

Reading: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3597338/ However I don't understand what a useful application for this is? can someone explain?

Working on some microwave stuff, read about this but can't understand the explanations online.

What I understand about harmonics, is when something is transmitted at high power, the antenna resonates on other frequencies besides the desired one. But Why?

I was studyng my exam of astrophysics laboratory, while treathing the optical aberration I've wondered: does radio telescope have aberration? Is a paraboloid antenna in a single dish affected by coma? and the radio telescope made by arrays of resonant structures? Maybe those are silly...

1 - Is a carrier wave always made by some kind of oscillating/oscillator circuit? 2 - Does modulation "modify" or better "modulates" the carrier wave to change the audio signal to amplitude or frequency modulated? 3 - What is the difference between a "radio mixer" and "modulator" do they have...

I get how analog ones with knobs tune by physically changing length of elements to match the frequency, but what about the ones that just have a screen and you type in what frequency you want?

Hi everyone! This is my first thread :) I've been working a bit with AC and radio, and would like to make a simple(-ish) circuit in which a 1-volt peak audio signal is stepped up to around 5 volts with a transformer, and is fed into a crystal oscillator to make a crude-but-effective AM...

Is it possible to design an unpowered antenna, (possibly some kind of RLC circuit) which will receive a radio wave at a particular frequency and then re-emit it at a lower frequency?

Hello, I have assembled the following AM radio reciever circuit: Purpose of the circuit: To receive AM radio signals and provide the output audio of these signals ( demodulated ). Circuit elements: L ~ 1.5mH , C ~ 300pF , Amplifier IC: LM324N , Diode: 1N4004 ...

A reasonably read and educated laymen, would response to a claim that science and technology still have no means to detect a big asteroid collision with earth, by saying that according to what he read and saw in communication channels reliable enough, an object of that size on course to hit...