What is Rf: Definition and 255 Discussions

Radio frequency (RF) is the oscillation rate of an alternating electric current or voltage or of a magnetic, electric or electromagnetic field or mechanical system in the frequency range from around 20 kHz to around 300 GHz. This is roughly between the upper limit of audio frequencies and the lower limit of infrared frequencies; these are the frequencies at which energy from an oscillating current can radiate off a conductor into space as radio waves. Different sources specify different upper and lower bounds for the frequency range.

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  1. D

    Why does glucose have a lower rf value than fructose?

    Even though their molecular formulas are the same? Fructose is an isomer of glucose and they are both cyclic and have 5 carbons so I was wondering why fructose was higher on the TLC plate than glucose. Thank you.
  2. B

    How can I accurately measure RF impedance on a wire with a glass coating?

    I'm trying to determine the best method of measuring impedance from a wire through it's glass coating to determine if the thickness of the coating is correct. At the moment I do not have the actual frequency, I just know it is in the RF range and that my impedance needs to be 50 ohms. I've...
  3. M

    What is Rf for Op-Amp Circuit w/ Vout=2V & Is=10mA?

    What is Rf --> Op_Amp 1. Consider the amplifier circuit shown. What value of Rf will yield vout = 2V when Is = 10 mA and Ry = 2Rx = 500Ω 2. The way I did this was by employing KCL: (Is that applicable?) The Attempt at a Solution Rx(Is) + Rf(Is) = Vout I'm actually not quite...
  4. P

    RF Signals - Radio waves or electrical signals?

    Hi all Sorry if this is quite a basic concept, but I am confused about RF signals. The way I currently understand it is that radio waves in space are an oscillating electric and magnetic field at 90 degrees to each other traveling through a medium. However, when you pass a radio wave into a...
  5. S

    What is a High Gradient RF Structure

    Can anyone tell me what a high gradient RF structure is? I think it is referring to the strength of say an electric field in a structure oscillating at radio frequency but I am not sure. I would appreciate any explanation.
  6. C

    RF fundamentals, how does bandwidth affect throughput

    I'm trying to get a basic understanding of RF DAC. If I have a DAC that does 100 MS/s with an 8 bit resolution, this translates to a 800 Mbps throughput. Or is this too simple? Now, how does the bandwith of a channel affect this? Say I have two 5 MHz channels. With two channels there...
  7. K

    Understanding RF Absorption by Metals in RFID Testing

    Hi everyone. I was wondering how badly aluminum affects RFID waves (860-960MHz)? Do they completely absorb, reflect, combination of the two? I'm having issues with my testing of RFID. I'm getting some dead zones and I think it could be because of the portal frame the antennas are mounted on...
  8. A

    Need guidance - RF engineer/DSP engineer interview

    Please guide me how to prepare for interviews for the post of RF engineer and/or DSP engineer. I finished my masters in electrical engineering and am looking for a job in these two fields. Topics and concepts that I must prepare and also the practical skills one must possesses (I have...
  9. A

    Why Voltage & Power Gain Aren't Applicable to RF Circuits

    I read that conventional (low frequency) circuit parameters - voltage gain and power gain are not applicable for RF circuits but I didn't understand why? Can anyone please explain.
  10. D

    Digital modulation and RF bandwidth

    Why isn't it possible to invent a custom digital modulation scheme that would use much less RF bandwidth than all the schemes available? What are the limiting factors that do not allow for high data rates to be coded so that the occupied bandwidth is much less than all the others like ASK, PSK...
  11. Z

    MATLAB Solving MATLAB Problems with R1, RF, R2 and w Variables

    I have such MATLAB problem: I create variables R1 RF R2 and w so: Code: syms RF R1 R2 w then I write expression: Code: 3*R1*w*(RF + 200)/((R2*w*29*i + 3)*(3*R1*w - 2*i)) which gives: Code: (3*R1*w*(RF + 200))/((3*R1*w - 2*sqrt(-1))*(R2*w*29*sqrt(-1) + 3)) why sqrt(-1) and not i...
  12. D

    Simple alternatives protoboards for RF circuit design

    I've found out very quickly that I can't use a breadboard for RF circuits, what is another choice? I know PCB's would be best but making them is very tedious for me. I'm new at this stuff so I plan on experimenting quite a bit which is another reason I want something quick and easy to replace...
  13. amylase

    Phase-Locking Proton Precession with 90° RF at Lamour Frequency

    As title. Thank you. In the context of MRI, why/how does applying 90 degree radiofrequency at Lamour frequency put proton precessions into phase? I understand 90 degree RF minimises net magnetic moment, such that there is least difference between number of protons in parallel (with...
  14. T

    Measuring distance from an RF beacon

    Greetings, PF'ers I've got a project where I'm trying to measure the distance from a stationary AM radio beacon transmitting a short coded pulse every 300ms or so to a non-stationary receiver. I'm dealing with a range of about 1 to 500 ft between points. I need to have at least 1'' accuracy...
  15. C

    RF question - Plane radio aliasing?

    RF question -- Plane radio aliasing? I hope this is the right place to post it. My buddy and I were working on a jet earlier and turned on the HF communication system to perform an operational check out of the system. We tuned the radio to 2.5 MHz and picked up a local AM radio station. The...
  16. B

    Understanding RF Power: A Beginner's Guide

    I have been reading about RF power and equipment. Can someone explain to me, in very simple language, how it works. I know that RF is a frequency range, and the amplifier obviously amplifies the power. Can you explain the coupling network, and how RF power is generated. Baisically the process of...
  17. P

    Difference between RF and Signal Processing Filters?

    I've designed both types of filters for years and can't really explain the difference in clear simple terms. I'm hoping somebody here can help me out with that. First, some working terminology: RF filter - a filter with a controlled input and output impedance, usually 50 ohms, to match the...
  18. ¡

    RF Distance Measurement Techniques (ToF+Interferometry)

    I am trying to design a system to measure the distance between two RF transceivers with as small of a resolution as possible. Time-of-flight measurement is nice and easy to do, but it has a poor resolution with low frequency timers. I am thinking of using a low-cost mcu that will probably have a...
  19. P

    Insertion Loss / VSWR of RF Lines

    Hello all, I'm not sure if any of you have ever used a device that measures RF transmission line loss and presents it as a graph of Insertion Loss (dB) vs. Frequency (GHz), but that is exactly what I'm trying to calculate. I've been looking through equations for days, and I just don't...
  20. W

    MSEE Electromagnetics, RF and Microwaves + ?

    The program I am looking at has an emphasis on Electromagnetics, RF and Microwaves. If I am looking at the telecommunications industry, what other exposure might be valuable? Would some course work in Signal processing or embedded systems be beneficial?
  21. Y

    RF Engineer from China Give Advice

    Hello. Yangman here. I come here write an advice. Do not study digital field in EE. Every day I meet some digital circuit chump who call himself engineer because he understand AND NOR NAND NOR and verilog. Just because you can make LED blink on Arduino do not make you real engineer. I give...
  22. W

    Quick question re. 1dB compression of an RF mixer

    I am quite inexperienced with actually using mixers, so when I was bombarded with specifications by a data sheet I was a bit intimidated at first. I think I have learned what most of the metrics mean thanks to a great deal of resources available online. I just have one question. The data sheet...
  23. S

    How to rate RF power handling of a part

    I made a DIY RF trasformer, and I want to know how much RF power can it handle, I want it to work from 500K hz to 3Ghz, have DC resistance 0.1ohm, L primary=5nH. There would be no DC current through this part. How would I know how much RF power my part handles? Do I send a voltage through the...
  24. W

    MS Electrical Engineering (Electromagnetics, RF and Microwaves)

    I was looking at the MS (non-thesis) in EE with a focus in Electromagnetics, RF and Microwaves. I realize jobs in military and commercial sector for communications, radar, etc. What else is out there? What kind of security would this degree offer me?
  25. dink

    RF Design: Guidelines for Driving 125MHz Square Wave w/o Ground Plane

    My take on RF in electronic design has always been, if the wavelength of the frequency you are working with is less than 10 times the length of the board/device(s), you should be using impedance matched networks for traces and cabling. Currently I have a problem where the wavelength is the...
  26. J

    RF manufactring companies in Australia

    Hi Australian citizens/ expats living in Australia What are some companies in Australia (including international companies that have Australian offices) that manufacture and produce Radio Frequency equipment ? I have a degree in RF engineering, but getting a f/t job in the area is...
  27. P

    Electrical Engineering Senior RF Project

    Hi Folks, I didn't know exactly where to put this post, so if it's in the wrong section, I apologize. On to it then. I'm in my final year in EE, and I want to work on a project that let's me become comfortable with RF/Communications concepts commonly run into in industry. I was...
  28. N

    What is the role of the feedback resistor in an op-amp circuit?

    I just started learning about Op-Amps. Working through basic equations seems straightforward, however I was curious about the function of the feedback resistor. As the name implies, one might infer the current/voltage potential "feeds back" from the output back into the input (I know there are...
  29. J

    What could be causing my RF transmitter and receiver to not work?

    Hey all! I have just constructed a RF circuit to try out. I made use of the T5-434-5V and the R5-434-5-128 transmitter and receiver pair and also the HT12E and HT12D as the encoder and decoder for the transmitter and receiver respectively. The schemetic I used can be found on page 6 of this...
  30. T

    How do I increase the range of this RF transmitter?

    What is the easiest, cheapest what to increase the range of this RF transmitter? Right now it outputs 8mW which gives it about a 500 foot range. I need it to be increased to about 40 miles line-of-sight. http://www.sparkfun.com/products/8946
  31. D

    RF Design Help: Re-Learn and Combine 2 Networks

    I'm having to re-learn RF design after years of not doing it. Can someone lead me in the right direction? If I have two RF networks, say two simple LC filters and I need to feed them both in parallel with the same source simultaneously, what are the steps? To make it easy, say each filter is...
  32. M

    Refractive index of materials at rf frequencies to make a smaller wire antenna

    I would like to ask a few questions. Does a table of refractive indices of materials at rf frequencies (say for TV) exists? Is there a way for me to estimate it for some materials? Are the refractive indices of these materials higher? Will those materials have low absorption losses at these...
  33. C

    Is it possible to power a small LED an RF signal

    I believe its possbile but wanted to ask if its possible to light a single LED light by and RF signal if its strong enough. I know there are LED's that are as low as 3 milliwatt that could work. Thanks in advance.
  34. R

    Finding the Right RF VHF Diode for GSM Signal Amplification

    Dear Experts, I am looking for some rf vhf diodes. could you recommend a particular model for me? I am quite new to this diode. Are these synonymously called microwave diode / MOSFET / rectifiers / field effect transistor? I am confused what should be the right diode to amplify gsm...
  35. T

    Engineering Exploring the Future of Engineering: Automatic vs RF and the Evolving Job Market

    Question is simple: Automatic vs RF engineering in future? And if you can tell some of precise jobs about any option. For example, I heard that, if you want to work in oil industry (on rigs etc.), automattics are way better option... Specific advantages about RF still not sure... (I know it's...
  36. H

    Basic T parameter table for RF design

    Can anyone tell me where I can find a basic T parameter table for RF design. One with the T parameters for shunt impedence in coaxial, series capacitance in coaxial, coaxial of length l etc...
  37. N

    RF radiation living near TV/radio tower

    Hi there, I noticed another thread about a guy who was considering living near a cell phone tower. People pointed out that he shouldn't worry because the amount of watts was low compared to tv towers etc. This makes me worry because I'm going to be moving into a property about 200 metres away...
  38. S

    Rf Plasma Simulation for material processing

    Hi to every one I want to simulate Rf lab plasma and DC glow discharge plasma But let me make clear one thing Consider me as a starter to both plasma physics and simulation So is there anyone who can help me in this respect to guide me from zero Regards
  39. T

    Engineering Finding a Job in RF Engineering

    Hi, I'm interested about situation in radio frequency engineering. Is there difficult to find a job in this profssion and what jobs exactly RF engineers do? Thanks.
  40. C

    Calculating RF Power: dBm-Volt-Watt Conversion

    Hello I have a basic question about the decibel -voltage - watt conversion. I am calculating pulsed RF power on the scope. The setup involved an RF transmitter connected to one end of an attenuator. The other end is connected to the scope. Sure I used 100 dB attenuator first and decreased...
  41. E

    Project: RF Transmitter in a metal box

    I have a question on my Junior Design project: My project will be going into a metal enclosure, but contains an RF transmitter with PCB antenna to allow it to be controlled from a USB port on a laptop. Our current plan is to make a 1"x1" glass opening to allow the signal to get out (2.4GHz, so...
  42. A

    Designing an Auto Match Unit for RF supply

    I've picked up a 13.56 MHz RF generator from eBay which I plan to use for an ICP plasma project (this is what it was designed for). I need to construct an RF coil and parallel capacitor with a resonant frequency of 13.56 MHz but I also need to construct an AMU as, as I understand it, as soon...
  43. M

    Help finding a specific RF chip

    The basic premises of what I am trying to do, is build a transmitter receiver circuit that has a signal strength identifier so I can calculate the distance between the transmitter and receiver. For example, if the chip is receiving 100% of signal strength (2mW) the distance equals 40 feet, and...
  44. M

    RF Detector: Understanding Video Bandwidth

    what is the meaning of Video bandwidh for rf detector?
  45. D

    LED comparator for RF circuits

    I have a question about making an LED light up when sensing audio. Right now, I'm using Super-Regenerative receivers and testing various components of them. Using a signal generator, my audio speaker squeals, as it should, when on the right frequency. When it's not on the right frequency, I hear...
  46. C

    RF beam width and antenna diameter?

    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?
  47. R

    Usefulness of an RF Circuit Design Class

    I'm considering taking an RF circuit design class that would focus heavily on transmission lines and microwave circuits. It's supposed to be a tough class but I think I would enjoy it because I really like E&M. The problem is that if I take this class I won't be able to take a photonics class...
  48. S

    2.45GHz RF microstrip Transmission Line design

    Hello all, I'm now working on the 2.45GHz frequency transmission line layout on the PCB. I would like to know whether there is a design guideline for the 1) minimum length of the transmission line. how do I know or calculate? I can calculate the width of the TL to get the 50ohm impedance...
  49. L

    Reducing RF power of video transmitter

    Hi, I have a tiny (.6"x.6"x.125") 2.4ghz video transmitter that puts out about 1mw or rf power. I want to severely reduce the output power in order to reduce the range of this transmitter. instead of a few hundred feet line of sight range I would prefer no more than 10ft, and as little as 2...
  50. S

    How to power an RF Linear Accelerator?

    I want to build a small linear accelerator with an energy level around 2-2.5 MeV and as much beam current as I can get without getting too exotic (but I'll be happy with whatever I can get initially). I will need a means of generating microwave RF with the power requirements, I'm guessing, to...
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