4
votes
0answers
88 views

How is extremely low frequency (ELF) radiation collected by a submarine antenna?

The U.S. Navy Project ELF managed to generate extremely low frequency (ELF) radiation at down to $\approx 76$ Hz (implying a wavelength of $\approx 3,945$ km!). I was curious, what kind of receiving ...
1
vote
4answers
422 views

Radio antenna producing waves in the visible spectrum

If a radio could produce waves in the visible light spectrum, what would the result be? This is a thought experiment that I've pondered for a few years now. I realize there are a few/many real-world ...
5
votes
3answers
1k views

Radio antennas that are much shorter than the wavelength

From my limited experience with ham radio when I was a kid, I expect transmitting and receiving antennas to have lengths that are on the same order of magnitude as the wavelength, and in fact I recall ...
1
vote
0answers
44 views

Is the inducing signal weakened to the extent it induces a signal in the receiving antenna?

Silly question ... An antenna is necessary to receive a transmitted signal from atmosphere, or otherwise. The transmitted signal weakens as it travels through the atmosphere. When the signal ...
0
votes
1answer
1k views

How do EM waves get detached from an antenna?

How does an electro-magnetic waves get detached from an antenna and spread to the space? While an antenna receives an EM wave, which quantity of the EM wave (electric or magnetic) is used for ...
1
vote
1answer
100 views

Getting a given wavelength radio signal given an antenna with real-world constraints

Supposing you are given a transmitting antenna of whatever type of metal is most commonly used these days, and supposing that you are applying an AC current with the intent of transmitting a 1 m ...
4
votes
2answers
398 views

Radio communication and antennas

I'm trying to understand how an antenna is able to understand, but have a few quesions: I understand that for an antenna to distinguish between 2 (or more) signals, they have to be in different ...
1
vote
2answers
265 views

Quantum Mechanics- Antenna emitting electromagnetic radiation

Radio signals are being transmitted in a frequency of $ 8.4 \times 10^9 s^{-1} $ and being received by an antenne that is capable of receiveing power of $ 4 \times 10^{-21} watt $ ($ 1 watt = 1 J ...
6
votes
1answer
3k views

Adverse Health Effects of Strong Radio Waves

A while ago, I was hiking near the Hollywood Sign in Los Angeles. When I got to the sign, I found out it was fenced off; with several signs and a security camera promising prompt enforcement. As I was ...
7
votes
3answers
1k views

How do radio telescopes work?

If I search online for how radio telescopes work, the found articles talk about how RF is on the spectrum, etc, how the parabolic collector is the aperture which contributes to the sensitivity and ...