Can a Tiny Antenna Transmit Long Wavelength EM Waves?

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Discussion Overview

The discussion revolves around the feasibility of transmitting electromagnetic (EM) waves using antennas that are significantly smaller than the wavelength of the signals, particularly in the context of very low frequency (ELF) waves. Participants explore theoretical and practical implications, including power limitations, antenna design, and the potential for using small antennas in various applications.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested
  • Conceptual clarification

Main Points Raised

  • Some participants suggest that it is possible to transmit EM waves with antennas smaller than their wavelengths, but the power transmitted would be extremely low.
  • There is a discussion on the necessity of matching the impedance of the antenna to the transmitter for effective transmission.
  • One participant proposes using small antennas to couple with surrounding objects to enhance the effective radiating size.
  • Concerns are raised about the efficiency of antennas smaller than a quarter wavelength at the frequency of interest, with some stating that such antennas would be "horrifically inefficient."
  • Participants discuss the implications of using higher frequencies, noting that smaller antennas could be more effective at these frequencies.
  • There is a hypothetical exploration of what would happen if an antenna were reduced to the Planck scale, with implications for the frequency and potential harm of gamma rays being discussed.
  • Some participants question the feasibility of using ionizing radiation (like gamma rays) for communication, noting the challenges in encoding information at such high frequencies.

Areas of Agreement / Disagreement

Participants generally agree that transmitting with small antennas is possible but acknowledge significant limitations regarding power and efficiency. There are multiple competing views on the practicality of using such antennas for effective communication, particularly at different frequency ranges.

Contextual Notes

Discussions include assumptions about antenna size, frequency ranges, and the nature of electromagnetic radiation. The conversation also touches on the limitations of current technology in relation to theoretical models.

Who May Find This Useful

This discussion may be of interest to those studying antenna design, electromagnetic theory, or anyone curious about the practical applications of transmitting EM waves with small antennas.

  • #31
lucas_ said:
So this is the reason why visible light can't be emitted by antenna?
no exception?

View attachment 246298How about chest x-ray machine. How do they direct the x-ray? nuclear decay since antenna not possible?

Visible light can be received by fairly conventional antennas at the nano-scale so if we can't emit visible light from an antenna it's not because of a physics limitation on EM antenna dipole radiation at that wavelength.
https://www.me.gatech.edu/featured_colarectenna
 
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  • #32
davenn said:
NO, it's dangerous
And expensive.
 
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  • #33
davenn said:
A little matching will do the trick
And a massive amount of copper in the ground mat, of course. That would count as the antenna, I suppose.
The VLF transmitting station at Rugby is another example of a notionally 'small' antenna in terms of wavelength. It has a long history of different installations, from as low frequency as 16kHz. One of the arrays transmitted on 60kHz (5km wavelength) and the antenna consisted of a number of 260m masts. That MSF signal did go a long way! The actual size of the array would be open to interpretation but it certainly was hard work going lower than a quarter wave.
But these small arrays did actually work and provide(d) usable services.
 
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