Antenna Definition and 418 Threads

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

Why there is not voltage or current just for 1ms if I connect a multimeter ground to the negative terminal of a DC power supply or charged capacitor? Why electrons in measure lead and DMM device cannot sense a bulk of electrons (or lack of it)? I tried with an 5kV DC power supply too. In an...

at a point they become plain waves, how much will they be attenuated when 'received' by a spiral log periodic antenna Vs another dipole? Would an H field created by a loop antenna have less attenuation?

A microwave transmitter, bouncing the microwaves off a parabolic dish, should have a small amount of acceleration due to the reaction of the microwaves against the dish. Would an arrangement of two dipole antennas, 1/4 wave apart and phase shifted by 90 deg., creating a cardioid pattern...

The photosynthesis light harvesters are called antenna. But when did people started to call it antenna? The earliest I can find is about 1970. I believe it should be even earlier.

I want to build a tilting wireless internet structure that is 24 feet high, with a fulcrum at 6ft. The idea is when I want to work on the device (which is 24 ft in the air), I can just unlatch the mast and tilt the structure down and work on it. I would like to have the pivot (or fulcum) at six...

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 recently bought a KiwiSDR and it's my first SDR so far. I was wondering, what antennas you guys recommendation for it and whether this recommended antenna is truly good for it (it was listed on the KiwiSDR site as a recommended antenna, but it's a bit pricey for me). I'm trying to find signals...

Hello. I have a very small antenna and I was wondering if it can receive and/or transmit low frequency signals (or if it can only receive/transmit high frequencies). Likewise, do I need a very large antenna to receive/transmit low frequencies? I've read somewhere on the internet that the...

Hello, I've been reading up on this topic and have a couple of questions. This videos shows what I am referring to: 1. What makes the electromagnetic waves from a dipol antenna spread out? There would have to be some type of force that pushed them outwards, right? 2. When the electromagnetic...

Suppose the performance of an antenna is calculated. How about its complimentary antenna?

What is the connection of relative permittivity and bandwidth of an antenna? Higher relative permittivity resulted in high wider bandwidth?

I want to do nanoantenna calculation using CST. However, there are many project template One for optical filter and resonator The other for Antenna-dielectric resonator I do not know which one should I choose? Could anyone advice me? Thanks.

1. A magnetic dipole antenna is used to detect an electromagnetic wave. The antenna is a coil of 50 turns with radius 5.0 cm. The EM wave has frequency 870 kHz, electric field amplitude 0.50 V/m, and magnetic field amplitude 1.7 X 10-9 T. (b) Assuming it is aligned correctly, what is the...

Hi; Let's imagine that I have an antenna and a biological tissue. The antenna emits the frequency of 1e7 Hz and I have a temperature increase x. When the antenna emits the frequency of 3e7 and 6e7 Hz the temperature increase is the same. How can I explain?

Hello everyone, for health reason, I just need to know from you what kind of antenna is the one in the photo attached, if it is a receiver or a transmitter and if it is safe enough. I will have to move on the first floor of a house right under that building (which is a police station if it can...

I have a fundamental question about the antennas made by using dielectric materials that I have not found a satisfied answer online. According to Wikipedia, antennas are described as, "In radio, an antenna is the interface between radio waves propagating through space and electric currents...

I have this piece of instrumentation that I am trying to model that I am not entirely sure how it functions. I am certain that it is a voltage monitor. It's basically a voltage divider (v_out = .017*v_in) enclosed in a grounded box with two holes on either side for the connections to the...

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...

If Cellular network towers are supposedly divided in cells , like this image , then why do we loose connection even when outdoors and not inside or near any buildings/cars. Also why is it common to see more than 1 cell tower near each other?

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.

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?

This is the AN/APG-81 AESA Radar antenna by Northrop Grumman currently found in the F-35 (photo from wikipedia article). It seems to have a very different structure than past AESA/PESA antennas. For example the APG-68 from the F-16 looks a lot like stacked, slotted wave guides to me. So...

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 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?

hello to everybody, can some help to make a ferrit rod antenna and to explain me thnx is for am radio, trf regenerative i have a ferrit rod 90mm diameter, and i have 0.5mm wire magnetic. this is the schematic , i make also the am receiver, but i don't know the ferrit rod(is problem i try to...

I have been trying to understand some trechnical aspects of the Holmdel Horn Antenna used to first confirm CMB. My references are: (1) https://en.wikipedia.org/wiki/Antenna_gain (2) https://en.wikipedia.org/wiki/Isotropic_radiator (3)...

Is it possible (and if so how practical) to overdamp a conductor wire that is many times longer than the wavelength of the incident radiation so that it doesn't reradiate any detectable amount, turning practically all incident radiation into heat?

Where can I find strict mathematical proof of the relation between antenna aperture and gain which is applicable to any type of antenna ? Aeff = Gain * (lambda^2) / (4*Pi) Aeff - Antenna Effective Aperture Gain - Antenna Gain lamdda - wavelength Pi - 3.14159 Many textbooks just show the...

I can't understand how a ferrite rod antenna works. Someone can explain it to me?

Is there a (dielectric) antenna of this shape ---o---o---o---o--- | | | | ---o---o---o---o--- i.e. a ladder? What is the good for such antennas?

Homework Statement A radio transmitting station operating at a frequency f=100 MHz has two identical antennas that radiate in phase (in other words, coherent with respect to each other). Antenna B is 10 m to the right of antenna A. Consider the point P between the antennas, and along the line...

please can somebody help, how to find in electronics shop online those components and to buy, is here juse one to make for all, i need juse one, which i can use for all projetcs L1 antenna coil: 470uH with 1 turn wrapped = 2 L2 antenna coil: 470uH...

Someone asked if it was possible to conduct electricity through a wire with a plasma. I ran across a article about a inventor who wanted to turn a antenna on and off very quickly. He said it was possible to do this by using a florescent light bulb as a element in the antenna. When a...

As part of my final project in my EE studies I was thinking if it is possible to read 125KHz RFID tags with a smartphone. I know it is possible with NFC (13.56MHz) and I was thinking about implementing a 125KHz reader. Is there any antenna in a regular smartphone that can deal with these low...

So the quality of my over-the-air digital TV reception has been getting worse over the past few months. Probably the digital TV antenna that I'm using is getting old and starting to degrade. Last night I resorted to trying different reflector combinations to try to boost the signal for the...

A radar antenna transmits 50kW at 10 GHz. Assume transmission is in a narrow beam, 1m^2 in area, and that within the beam, waves are plane waves. The wave is reflected from an aircraft but only 1% of the power propagates i the direction of the antenna. If the airplane is at a distance of 100km...

Do receivers only receive signals or they emit emf?

Hello, I'm looking for some insightfull answers for the following topic: I have a (slotted) waveguide where multiple (50) antennas (for sending and receiving) are located in a slot that runs along the waveguide (200 meters long). On both ends of the waveguide are probes located for the wireless...

Hello all, I have a problem with a typical style of problem I seem to always struggle with. Just to clear this up, I am studying for my comprehensive exams later this summer. So I am going through past problems to bone up on the last two years of grad school. At which point I came across this...

I am contemplating about pursuing EE bachelor. My goal is to deal with antennas, signal processing, electronic communication, etc. But all the curricula that I have examined (USA), universities don't seem to offer any courses on antennas. Sig proc - yes, and so are circuit analysis present there...

What i need are the ff: basic guidelines on how to create an outdoor antenna (you can send links :)) the most suitable type of antenna that can receive 70 MHz tv station frequency. The antenna will be mounted less that 3 m from the ground. computations that i need to know (you can also send...

I am studying to about maxwell's equations on the electric and magnetic field. First of all, just do the example and exercise: https://www.princeton.edu/ssp/josep...ide-to-maxwells-equations-D.-FleischLEISC.pdf I have this dipole antenna...

Let's say we have a path Length AC. Point A transmits a signal at Ptransmit. From Friis' Path Loss formula: (assumming Gain for receiver and transmitter antennae are 1.) ##P_{received} = P_{transmit} (\frac{λ}{4π* LengthAC})^2## ,when point C contains the receiver. What if I divided this into...

First time poster long time reader. If i have a half wave dipole antenna with a certain length and I am using a VCO to drive that antenna at lower driving frequency do i get EM at the length of twice the length of the antenna but just at a slower emission rate? example, if i have a half wave...

Hi, I am learning about different antennas like for radio and internet wifi bandwiths and I came to the Yagi antenna. From what I understand, the people use this antenna both for receiving and emitting signal. For example, for pentesting (handshakes and all that) and for radio emitting (also...

Is there any particular reason to choose a square shape antenna like http://www.globalspec.com/reference/70592/203279/2-5-4-by-4-wavelength-rectangular-microstrip-antenna instead of a circular shape?

Hi , what happen if a half dipole linear antenna is placed inside an electric conducting resonant cavity? The cavity itself is the conductive ground of the half dipole antenna. How can I solve such problem in which the cavity works as resonant cavity and it is part of the antenna itself? Cheers...

Hi the difference between a loop antenna and a magnetic probe (B-Probe) is only that the loop antenna works in far field and B-Probe works in near field? The standard features of magnetic antenna (antenna factor, impedance matching, radiation patterns, efficiency, ecc) have the same definition...