Antenna Definition and 418 Threads

Does the length of an antenna feed affect the length of the antenna one should use? Intuitively I'm thinking 'NO' since in some applications the user supplies (variable length) antenna feed cables, but the antenna is still made to be resonant to the application frequency. BUT in the RF...

Hi, We're trying to build a simple antenna that's able to pick up a frequency of 457 KHz from a maximum distance of 20 metres. I'm totally new to this stuff, so I looked up the yagi antenna and some formulas used to determine the length of the antenna, but the results I got were huge...

Why is it that an antenna length must be somehow proportional to the wavelength of the frequency

I am building a resonant RLC network in which the inductor is actually a loop antenna that will pick up changes in magentic fields and represent them as a voltage. Is this configuration actually feasible where the loop antenna is both the voltage source and the inductor? Also slightly related...

I found in many sources describing microstrip antennas are 'low profile'. Well, I know several antenna parameters like radiation pattern, antenna gain, intensity, directivity etc. But what is this 'low profile'?? Can anyone tell me what sort of property of an antenna does the term 'low profile'...

Hello community Sorry if this is a repost, but I don't find what i am looking for. I am reading the book "anntenas", by Kraus and Marhefka In page 30, says the antenna impedances are complex. Z{\tau} = + R{\tau} + jX{\tau} .. Could anyone please tell me what does the complex part imply in...

If electric energy is supplied in the form of high voltage & low current & if the same energy is supplied in the form low voltage & high current will there be in difference in the photons emitted by the antenna?the frequency is same for both the cases.One electron can interact with just one atom...

I am looking for textbooks or reference material that will help my design a loop antenna to operate in the long wavelength spectrum(60Hz to 100KHz to be exact). I understand there is more to consider than just Faraday's law and am looking for a book that can help step me through the process of...

Homework Statement The solution does not take into account Gain of transmitted antenna. Why? From friis eqn, Pr(db)= Pt+Gt+Gr-Lp, but soln. omits Gt soln below

Hi, Im looking for some one who has worked on or knows the concept of near field antenna measurements. If there is anyone here I would really appreciate that you reply and answer some of my questions. I am having trouble with the sampling part for creating my plane wave spectrum.. I am...

it seems like looking at beam patterns from directional RF antennas the beamwidith is something like inversely proportional to the parabolic reflector diameter. why can you make an almost perfect strait parallel beam of light but not with RF?

Good Morning Can anyone help me understand why, apparently the physical length of a monopole end feed wire for a crystal set need to be ½ the wave length of the desired signal. The reason I ask is, that I understood that, if you have a variable coil in series with the antenna, the...

I have a antenna in my room & it runs to my tv tuner. Just curious why the reception of the signal is affected by a person moving around the room? Even swaying your arm slightly affects it. thanks.

In the case of a loop antenna with uncompensated inductance, the magnetic field generated by the current in the antenna is in antiphase to the incoming magnetic field of the EM wave. So it is believable that the current which causes cancellation of the flux through the antenna is the maximum...

i live in a hilly location where i have very difficult radio reception, so i am always futzing around with my little "active" antenna for FM radio (PBS). i notice that reception always improves as i move near the antenna (like within 3-5 feet is noticeable), and gets much better if i just touch...

Hi - the building community where I live has just installed a few Wi-Fi ("sector", I believe) antennas and one of them is at same height and facing straight into my apartment. They are probably 10-15 meters across my apartment. I have a one year old son, and concerned about any health effects...

Hi, Is it possible to direct connect an antenna working below 100MHz to an oscilloscope with coaxial cable and see the radiated signals? Thanks.

Hey guys, Last night around 12 midnight, I decided it would be a good idea to climb a nearby antenna next to my house. It is about 143 meters high, and I went all the way to the top. However, I have been googling around, and I think I might have climbed an AM tower antenna, and I am REALLY...

According to this website for building an antenna the optimal length of the rods is 7 inches. Can I take 7 inches of copper cable and wrap it around a ferrite core to make a smaller version of the antenna that is just as effective? http://uhfhdtvantenna.blogspot.com/

Suppose we have a fixed coordinatre system (x,y,z). Suppose an antenna is horizonally polarized. Is the orientation of the E field fixed as a function of (x,y,z). Or does it change?

Dear all, This question is related to the radiation of a UWB antenna. If I feed a Gaussian pulse to a UWB antenna, would a differentiated gaussian pulse radiated? It seems so as in the tutorial paper (attached) by Wiesbeck says that "any antenna differentiates any signal because antenna do...

Hi! We entered a competition, and got the following question: Modern hearing instruments use wireless communication between the two ears to optimize the performance of the sound processing. The wireless link is typically a magnetic link in the lower MHz range. With this kind of link, each...

I'm having a little trouble using the Latex thing so I've only used it for some of the equations. Homework Statement Elevation control of a tracking antenna. Equation of motion for the system J\theta^{..}+B\theta^{.} = Tc+w ... Equation 1 (those dots are meant to be above the thetas, but I...

Homework Statement Two antennas located at points A and B are broadcasting radio waves of frequency 96.0 MHz, perfectly in phase with each other. The two antennas are separated by a distance d=12.40m. An observer, P, is located on the x axis, a distance x=55.0m from antenna A, so that APB...

It is possible to use a parallel plate capacitor as an antenna to pick up the electric component of an electromagnetic signal ? Thanks .

In my electromagnetic engineering class we were talking about Hertzian dipole antennas with an oscillating current source (transmission line) driving the antenna. As part of the description of the behavior as the two ends of the antenna have opposite charges an electric field is created from...

Hi, I come across these 2 questions on a website: 1. Why are the antenna on TV and Radios about the same length 2. Why is the antenna on the cellphone (i.e. the older versions) smaller than the Radio antenna? My answers to these 2 questions are: Firstly, the waves that the cellphone...

A very basic question: the signal reception requires that the receiver be at the communication region of the sender? Or what is important is the intersection of the comm. range of both sender and receiver? A practical example: Assume that both sender and receiver have the same hardware, antenna...

Hey guys, I understand remote control cars and such use their little antennas and shoot radio waves to the car and control it... My question is can I make some kind of device such that I can remove the antenna on the car and instead hook up to the reciever a digital input processor which will...

greetings all, I am trying to start some undersampling RF to ADC hobby stuff. I am looking at this development board: http://www.digikey.com/scripts/dksearch/dksus.dll?KeywordSearch?Keywords=ADC11C170HFEB&vendor=14 I am having a little trouble understanding how to connect the receiver...

If Light is EM wave, and antenna can emit EM wave, then can an antenna emit light? Is this a matter of designing the antenna correctly or is there something fundamentally wrong about this reasoning?

This looks to be a much more active forum than another I tried to get some feedback on recently...same question, hoping someone here can weigh-in on this before I potentially make a mistake. I'm installing a mini PCI WLAN card (802.11n/g) and antenna inside of a small form-factor PC. The...

32m away from my house there is a 5m tall cellular antenna. to prevent from electromagnetic waves from it, i have placed a metal net 1.5mm/1.5mm a man came to my house to measure the radiation and it said that there is radiation in the house... i have 3 questions; 1)does the metal net...

Hi All, I understand that if you have a lossless transmission line and a lossless antenna and there is a mismatch at the antenna/transmission line junction, no energy is lost. If the transmitter is delivering 100 watts into the line, 100 watts will be radiated from the antenna. I'm...

Hi All, I'm currently wrestling with trying to understand the theory behind radiation from a dipole antenna. Little by little I'm putting the pieces together but I need verification regarding a conclusion that I have drawn although I have not read it. An antenna has a near field and a far...

Antenna Gain?? :confused:Hi all, I am really confused by the subject of antenna gain. I have no problem with the idea of the idea that an antennas performance should be related to how welll it focusses radiation relative to an isotropic emitter. Bus as this gives a figure greater than...

I made the mistake of buying a cheap Chinese phone on Ebay (don't buy phones from Shaosan Li) The reception was useless and in only worked in direct line of sight of a phone tower less than 50 m away. With nothing to lose I pulled the back off the phone and located the internal antenna...

hi all, what exactly is the gain of an antenna, and what is the difference between the gain and the directivity? also, what is the EIRP, is it the same as the radiated power? and how can the radiated power be greater than the transmitted power? (EIRP= transmitted power+gain-losses in dB)...

Let's say we have a dipole antenna that we are using to radiate a signal. The dipole antenna (think rabbit ears) has two ends that appear to me to be open circuits. Maybe my problem is that I have too much circuit background and not enough EM, but how does current flow through these rabbit...

Hi - I live full time in an RV that is surrounded by aluminum - essentially a faraday cage, except for a few rather small windows. I'd like to mount a WiFi antenna on the roof and run a cable in a window or thru a small hole. Basic issue - how to get a good signal from a campground WiFi...

please anyone tell me the relation betweeen wave length of em wave and antenna dimention

Hi I have this question for sometime, and until i found a recent post here on this forum (wavelength and aperture) i thought i was the only person who just plain didn't get it. My questions arises firstly when i consider antennae and as roughly quote from the many texts i have read "to...

Modulation is the process of impressing an information bearing signal to a carrier for effective transmission over a long distance. example Am and FM used in radio transmission Analogue baseband signals of 0-4000Hz are shifted to 60-64Khz range. Communication systems often do not carry...

hi everyone, a friend of mine bought a multi-sim iphone clone from china. i was so amazed at this. as a hobbyist, i want to create my own pc-based multi-sim gsm terminal. so i want to use 4 gsm modules(sim300). one for each gsm-provider here in my country. but my problem is i want to use only...

Help! I would appreciate thoughts on TV antenna’s and antenna principles. After the digital change over I’ve lost several channels. A couple of channels come in sometimes pretty good, but with continuous minor annoying breakups. I would like to understand a few principles before I attack in...

I searched around this forum and google but couldn't come up with anything definitive. Now, I know that the radio in your car needs an external antenna because your car acts as a Faraday cage, and most radio waves don't make it through. But I'm having some reception issues. I own a 1986...

Hi, I read the following on seti.org: "Our earliest TV broadcasts have reached several thousand nearby stars, although any alien viewers would have to build a very large antenna (thousands of acres in size) to detect them." I guess that signals have got very weak...( does it mean...

If you could get a circuit to oscillate quickly enough, could visible light be produced using a simple metallic antenna?

I have been looking everywhere for a simple, easy-to-understand explanation of antenna dimensions/properties. I am referring to omni-directional that are basically just a piece of wire that stands perpendicular to the ground, like Wi-Fi antennas. I've read that the length of the antenna has...

I am transmitting an electromagnetic field from a loop antenna of 0.28 radius to one with 0.216 radius. I know the antenna factor of the receiving antenna but when I add it to the measured field strength, it does not equal my calculated transmit field strength. Should the shorter antenna be...