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. B

    Determine a cable core diameter for RF current carrying loop

    Basic Question Alert ! (I need to brush up my basics and need your help) Problem Statement: I wish to make a current carring cable loop to generate a controlled magnetic field. http://hyperphysics.phy-astr.gsu.edu/hbase/magnetic/curloo.html As I understand, the magnetic field generated depends...
  2. F

    I Exploring the Existence of RF Photons in NMR Spectroscopy: A Scientific Analysis

    Some will claim that RF energy being composed of photons can only be accepted on faith because there is no experimental evidence and there probably will be no experimental evidence due to the comparatively long wavelenghts of RF waves. But the technique of NMR (nuclear magnetic resonance)...
  3. N

    Transmit/Receive analog signals

    I'm completely new to transmitting/receiving signals, but I wanted to get a scope of what kind of components are out there that I could use to build this system. I wanted to read the voltage drop across a resistance thermometer (Vt) and send this signal wirelessly to another circuit, where I...
  4. N

    High power low frequency RF Amplifiers

    Hi all I am searching some commercially available industrial grade power amplifiers: 1.In the frequency range of 80 KHz to 140 KHz with output power of 2 KW to 50 ohm load in pulsed mode (<10% Duty Cycle 2.In the frequency range of 400 KHz to 450 KHz with output power of 5 KW to 25 ohm load...
  5. Plat

    How are RF harmonics affected by the shape of a waveform?

    How can the power/amplitude of a particular RF harmonic be calculated? I would assume it is some well-defined fraction of the amplitude of the main frequency? Do RF harmonics from a square-wave drive appear only on the even, odd, or both, multiples of the base frequency? How do high-frequency...
  6. C

    Why Do EMF Meters Measure ELF/VLF Differently?

    Why do EMF meters measure ELF and VLF in flux density units but RF in power density units? Is it because ELF/VLF have low power density and high flux density, and RF has high power density and low flux density? They are all EM waves, right? what's driving the difference in measurement units? thanks
  7. enginej

    Calculating the total power received by an antenna

    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...
  8. E

    Understanding RF Power Measurement: Average vs. Composite Power

    What is the difference between average and composite power?
  9. C

    What are the difference between electrical current and RF?

    Hi. This might be really basic. But I am really struggling to grasp the difference between electrical currents such as AC and DC and RF. For the case of AC current, it alternates currents at a certain frequency.. which makes me wonder how AC and RF are different. Also, if you could, could you...
  10. D

    Expert RF Hardware Design Tips & Resources for Full Stack Engineers

    Hey Everyone, I am starting a new job in a few weeks. I have EE background with strong academic and professional background in power electronics, digital hardware design, control systems and low frequency analog circuit design (<100 kHz). I always joke around that I am an full stack hardware...
  11. D

    Genetics double recombination counted twice in terms of RF

    When mapping out re-combinations of a crossed trihybrid you have to account for the proportion of the offspring who do not share parental genotypes. Of the 8 possible genotypes stemming from this mating, 6 will be recombinant and two will be of parental genotypes. Your idea is to Map out the...
  12. B

    RF Network for 2-Way Communication, Security, 3.5x1.5mi Community

    I need a RF network that has this : 1) two way communication. 2) Security 3) can work in a 3.5 x 1.5 mile community : with houses, trees, buildings and a park ( https://en.wikipedia.org/wiki/Box_Hill_North,_Victoria). 4) have about 1000 endpoints. 5) low power and low cost would Xbee be...
  13. E

    What is the composite power of multiple RF signals?

    I need to calculate the composite power at the input of an RF distribution system, is it just the sum of the signals in milliwatts at the input? I can measure each individual signal with an a spectrum analyser but I do not have a power meter to anable measurement of the total power.
  14. G

    How to Model a Coaxial Cable System Excited by an External Field in COMSOL?

    hi i m looking if there a method to introduce a systema into COMSOL (like coaxila cable) and this systems excited by an external field
  15. Lattitude

    How is RF in-homogeneity in NMR addressed?

    IN NMR, the sample is placed in the probe and is excited by the coil using RF fields. But, errors creep in due to the inhomogeneous nature of the B1 field and also the errors in the static magnetic field(which are taken care of using shim coils). In some of the research papers I read, they just...
  16. P

    Particle accelerators and timing for particles

    So, I found this document that talks about rf cavities at lhc https://home.cern/about/engineering/radiofrequency-cavities Can you please explain me what i underlined Means? If i understood when the particles achieve the velocity the scientist want them to achieve they get into the cavity when...
  17. N

    How to measure output voltage of B200?

    Hi, I am a new student and trying to to measure the power and voltage output from B200 SDR device (https://www.ettus.com/content/files/b200-b210_spec_sheet.pdf) using oscilloscope (TDS3000 Series: https://www.atecorp.com/ATECorp/media/pdfs/data-sheets/Tektronix-TDS3000_Series_Manual.pdf)...
  18. J

    Pointer to data wanted please -- looking for a primer on phased array radar

    Fair warning: I can handle basic physics stuff, but probably nothing post-collegiate. :) Specifically, I'm looking for a primer on phased array radar that will tell me two things: 1) what are the practical physical (antenna) requirements for running a PAR system in the 800MHz/5GHz bands, and 2)...
  19. _maxim_

    A Best coil design for homogeneus NMR RF pulse on liquid discs

    Hi there, we have a NMR spectrometer equipped with a standard bore 54mm cryomagnet working at 14.1 T (600 MHz Larmor Frequency) produced by Oxford. I would implement a special probe capable of generating a RF pulse and reading a NMR answer from a sample that is not standard for such...
  20. K

    Opamp for MF/RF ranges (1.0-1.2MHz)

    Hello! I have a bit of trouble finding general op-amps that can amplify at medium frequency ranges, and with a good enough gain of 200 or 46dB. My max desired operating frequency is around 1.2MHz so I don't really care if it no longer amplifies much at frequencies higher than this. I am aware...
  21. H

    B Can You Identify This Mysterious RF Signal at Night?

    Looked at a RF spectrum that came from the IF output on a radio so it was not tuned thru the radio filters, just whatever the HF antenna was capable of. A pulse went across the entire spectrum slow enough to see it sweep across the screen. The pulses were not regularly spaced but came in...
  22. N

    Shield against induction of sounds from remote source of RF

    It has been demonstrated that it is possible to make humans hear sounds using waves. Abstract From Journal of Applied Physiology Is there a practical method for shielding? I mean using materials for simple attenuation, and/or altering characteristics of waves (frequency, phase and/or amplitude).
  23. N

    How to calculate the time delay based on a function of antenna angle?

    Hi everyone, I am a new student who is studying on collecting data from TV signal. I hope everyone can help me for ideas. I am having spectrum analyzer which can define a TV station around me, so I chose 4 stations WHUT-TV [584MHz 590MHz], WPXN-TV [590MHz 596MHz], WTTG [60 MHz 608MHz], and WNVC...
  24. WeeChumlee

    Solving Transimpedance Circuit: Find k in Terms of R1, R2, and Rf

    Homework Statement The circuit of FIGURE 2 is known as a transimpedance circuit used for the measurement of very small currents. Derive the relationship between the output voltage V and the input current I; i.e. if V = kI find k in terms of R1, R2 and Rf. Homework EquationsThe Attempt at a...
  25. V

    I What is the approximate impedance of an RF plasma "antenna"?

    I've searched high and low for data regarding this from scientific papers to books and I cannot find anything in regards to the approximate impedance to excite a vacuum vessel to plasma state. In particular I want to built a RF Plasma cleaning chamber, however, I am not sure how to design the...
  26. F

    Wireless, RF, inverse fourth power law vs inverse square law

    When, in wireless communications, does the inverse fourth power-law become relevant? My understanding is that is that what cause the average signal power to degrade to the forth power is cancellation from self reflections. So by my way of thinking, an LOS point to point system, like a...
  27. C

    Capturing an RF signal from a remote controller

    Hello! This is a question that's been on my mind about RC drones for a while now but it's not really something you can just google. Is it possible to capture a transmitted signal from a remote control (with a sensitive receiver other than the one mounted on the drone) and store it in memory...
  28. C

    Understanding an RF remote control

    Hello! This question may be a little too specific but if there are any drone enthusiasts out there they might be able to help me out! I'm trying to understand the transmitted signals from a remote control to an air drone. When the user of a remote control, let's say, pushes up on the joystick...
  29. spearme

    A Silver RF magnetron sputtering targets

    Hi, I'm hoping someone out there can help me. I've vented my system to clean her out this week and as I was checking my targets I noticed that the whole sputtering surface of my silver target was white. I've been able to clean the white layer off but have no idea what it is or how it happened...
  30. berkeman

    RF absorbing sheet materials? (5GHz)

    Has anybody used thin RF absorbing sheets or tiles to attenuate RF radiation off of PCB assemblies? I've seen it used many years ago, and I have a 5GHz application that I'd like to try an absorbing sheet on. The PCBA is a few cm on a side, and the sheet or sheets would be applied directly on...
  31. A

    RF Module Communication for Hobby Project: Using TTL or Encoders/Decoders?

    For a hobby project I got a couple of RF modules, a QAM rx2 433 receiver and a DSQAM tx1 transmitter. I understand they need some kind of TTL to work, would just using some NAND gates hooked up to the transmitter and receiver be enough or do I need something more fancy like encoders and decoders?
  32. B

    Correcting Misconceptions about the Frequency of RF Pulses in MRI

    The magnetic moment of protons precesses at a frequency ω0=γB0 about the static magnetic field. In order to move the magnetisation vector into the transverse plane the RF pulse must be applied at a frequency ω0. However, as B1 (the field strength of the RF pulse) is << B1 how is this possible...
  33. Y

    Radiation emitted by wired keyboard

    Hi, I heard before that wired keyboards emits radiation when a key is clicked. My goal is to build a keylogger based on this phenomenon (for fun, of course). I've already seen some variations of this idea, but they were all using wireless keyboard, where it is much more simple to detect and...
  34. F

    Testing RF Waveguides: Using VNA for Freq, Power & Avg

    Hi there i am trying to test RF Waveguides and testing them. Something does not look right to me. i am using Freq range, data points, power and avg option is there anything special we use on VNA for testing Waveguides. Regards, Faheem
  35. H

    Amplifying AD9850 DDS for 5Watt output. OPamp or RF FIT?

    Hello. I am looking to amplify a sinusoidal signal generated from an AD9850 DDS. It appears the output is 1Vpp @ 27.12MHz when connected through a 50ohm cable to an oscilloscope. I need the total power output to be 5watts after amplification with a very clean sinusoid. The output will be...
  36. Joel Shearon

    RF Energy Harvesting Batteries

    Hey Physics Forum! So I will try to give as much detail as possible and needed without dragging on. We have an RF source at 5.8 GHz producing -17dBm and we eventually amplify it close to 27dBm (so we get as close to 30dBm out of source antenna as possible). We are using 5.8 GHz slot antennas...
  37. Ryan Reed

    B How would you calculate RF cavity dimensions?

    In a linear accelerator that use cavities and microwaves or radio waves to accelerate particles, how would one find dimensions such as cavity openings, cavity size, length between cavities, etc.
  38. GhostLoveScore

    Why Doesn't a Transmission Line Radiate All Its Power Away?

    This question is about transmission line that I use between my Ham radio and the antenna. We a transmission line that is made of two parallel conductors close together. The current in one conductor is exactly the same as the current in the other conductor, but flowing in opposite direction...
  39. D

    Protect Your Amplifier Modules with RF Pre-Amp Protection

    I have these great Mini-Circuits amplifier modules (ZFL-1000LN+) I use all the time that keep getting blown by a nearby HAM radio operator. Can I protect the input to this module by soldering two anti-parallel fast switching diodes from the input connection to ground?
  40. U

    Questioning RF Frequency & Filters

    My question is about RF frequency... The RFs are electromegnetics waves...That means they are one type of Light waves... right?? The other question is about perticular frequency of RF signals...When we want to transmit or receive some perticular frequency... we tune our radio at that perticular...
  41. uzi kiko

    Impedance matching and tuning of RF coil

    Hi everybody. I am trying to understand the concept of impedance matching and tuning of RF coil. As far as I understand there are 2 stages: At the first stage I should match the coil to the source (Let's say with L network method) and the second stage is to tune coil to the desirable frequency...
  42. uzi kiko

    Impedance matching and tuning RF coil

    Hi everybody. I am trying to understand the concept of impedance matching and tuning of RF coil. As far as I understand there are 2 stages: At the first stage I should match the coil to the source (Let's say with L network method) and the second stage is to tune coil to the desirable...
  43. S

    Input/Output Voltage Class C RF Amp

    Hi all: I am a new member here with my first post. I am an adult learner trying to self-teach RF electronics. I have been working through David Rutledge's Electronics of Radio, while building the NorCal 40A transceiver. I am getting caught up on understanding the Class C RF power amplifier...
  44. rushi121

    How to find a right RF module for a project?

    I am a product developer but not an electronics engineer. I am doing a cost analysis of a product idea for my company. The product will need something like this... There will be two small portable devices (A and B) 1 meter apart (not in line of sight since A can be in pocket). Product A will...
  45. C

    Ordering Rf of Aspirin with Polar Eluents

    Homework Statement arrange the following eluents in an increasing order of Rf of aspirin ethyl acetate, n-hexane, n-butanol, methanol Homework EquationsThe Attempt at a Solution my order is n-hexane < n-butanol < ethyl acetate < methanol but the order is wrong. i am thinking: aspirin is...
  46. R

    How RF Antennas Work: A Beginner's Guide

    Okay, sorry for my frustration at this fundamental subject, but I am going completely insane not understanding it! All this near-field / far-field stuff is messing with my head. I simply want to know how RF works. Let's start simple. HOW IN THE WORLD IS AN RF SINGAL MADE!? Let's say I have some...
  47. P

    Best material to reflect for 35GHz RF

    Hello everyone. This is my first post.. I have been given the task of building some large RF reflectors that will reflect 35GHz RF energy. Can anyone give me an idea of what material / thickness of material I could use. For an example.. Would a pyramid made from wooden pallets covered in...
  48. Mr.Robot

    Conversion of distortions in RF waves to Electricity

    So,the thing is i want to convert distortions generated in two RF signals in Electric energy. Actually i want to store it and then use it. example- Charging my smartphone. So what will be the basic requirements for me to do so!
  49. J

    RF Energy Harvester: Villard Circuit, Supercapacitor 3.7V 2000mAh

    I am using RF energy harvester circuit to charge mobile in my project.The rectification part is done by Villard Voltage multiplier circuit .I need to used a supercapacitor to store the harvested energy .As the battery rating of the mobile phone is 3.7V and 2000mAh.So can i use 0.33 Farad 5 Volt...
  50. J

    Breakdown of Air due to RF fields

    I'm just trying to think of a qualititive solution to the following thought experiment: I have an RF source of very large voltage driving a signal towards point A (say, a capacitor or a dipole antenna). The source itself is not really part of this experiment, but I just want a sinusoidal...
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