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0
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2answers
148 views

Does a simple copper wire with an AC current create EM waves?

I want to know if a household AC current flowing through a simple copper wire will radiate EM waves? If yes, up to what range and can they be called radio waves?
5
votes
0answers
69 views

Is there any antenna with a single null?

If we designate the origin (the reference point from which all displacement vectors are measured) $\vec{0}$, and If we consider a sphere $\mathbb{B}\left(\vec{0},\mathcal{R}\right)$ of radius ...
4
votes
0answers
141 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 ...
3
votes
0answers
83 views

Did Penzias and Wilson need such a large horn antenna to discover the CMB?

Penzias and Wilson discovered the 2.7K Cosmic Microwave Background (CMB) Radiation using a 6 meter horn antenna, along with a cryogenic low-noise detector measuring at 4 GHz: ...
2
votes
0answers
87 views

Signal strength drop-off from a geosynchronous satellite as a function of angular pointing error

If we have a compact antenna used to communicate with a satellite in geosynchronous orbit somewhere between the $K_u$ and $K_a$ bands of the spectrum (for high broadband applications where we can't ...
2
votes
0answers
46 views

Is the electrical signal delivered to a load by a receiving antenna always $\propto \frac {\partial}{\partial t}$ of the $\vec{E}$ or $\vec{B}$ field?

A time-varying $B(t)$ field through a loop antenna induces a voltage proportional to $\dot{B}(t)$. A Hertzian dipole along a time-varying $E(t)$ field also induces a voltage across a load--while I ...
1
vote
0answers
26 views

How is it that 62" is the best length for 72Mhz receiver?

According the this article (which was published somewhere in 2005-2008 I think, but it's still comes up first in Google) the best length for a 72Mhz receiver antenna is 62" (~157.5cm). This puzzles me ...
1
vote
0answers
81 views

Hertzian dipole in time varying electric field

Suppose we place a Hertzian dipole (short, ends loaded with capacitance) in a time varying electric field $\vec{E}\left(t\right)$, with magniture $E\left(t\right)$ and direction as shown in this ...
1
vote
0answers
50 views

Does shadow fading change if obstacles are fixed?

Given a RF sender and a receiver, suppose the obstacles between them are fixed, both their material and dielectric properties, does the path loss caused by their shadowing vary? If yes, what causes ...
1
vote
0answers
46 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 ...
1
vote
0answers
127 views

Can mu-metal reduce the negative effect of metal close to low frequency RFID antennas?

I have an 134.2 khz RFID antenna for sport events which is basically a 1x1 meter square sheet of rubber with 3 loops of antenna cable embedded. The problem is that the transponder recognition range is ...
0
votes
0answers
22 views

Difference between directional and omnidirectional transmission or reception?

It is suggested that the next generation wireless technology will be highly directional since this increases the signal gain (MIMO) and decreases interference. How will the receiver still be able to ...
0
votes
0answers
31 views

Could a 1kHz EM field be detectably disturbed by an action potential?

This might be completely off base, but I'm wondering if this would be possible. Neurons fire action potentials that can be modeled as low-intensity (~100mV) EM pulses of 1kHz frequency (up and back ...
0
votes
0answers
50 views

Diffraction between two beams of right- and left-circularly polarized light

If we have an optical / microwave two-way relay, my understanding is that one strategy to avoid destructive interference-based signal degradation is to use orthogonal linear polarizations. Here, ...
0
votes
0answers
26 views

Covariance of rayleigh channel

f=[f1 _f2_ f3]; g=[g1_g2_ g3]; f1,_f2_,f3,_g1_,g2,_g3_ are all independent identically distributed zero mean complex random variable. h= elementwise wise Schur-Hadamard product of f and g. What is ...
0
votes
0answers
270 views

explain how does Rectenna work to someone with some college level physics

I understand that rectifying antenna (rectenna) is supposed to convert electromagnetic energy to electric current however I do not understand how it's really working. I do get that it's kind of like ...