# 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.

View More On Wikipedia.org
1. ### Submarine communications and RF skin depth

In conductive media like seawater, EM waves experience attenuation related to their frequency. The skin depth formula calculates the depth at which ##e^{-1}## attenuation is reached. The skin depth is inversely proportional to frequency. In practical terms, only extremely low frequencies (eg 80...
2. ### I What determines RF cavity size in particle accelerators?

In a particle accelerator what determines a RF cavities size? Do they follow the same regulations drift tubes do when calculating there size? What formulas would a physicist use to build a RF cavity?
3. ### How to synchronize the RF source having delay over time?

I want to synchronize the RF power supply (having jitter or delay over temp/time) to RF reference frequency with a digital delay generator, and I thought of two ways. 1) phase locked loop: it is commonly used for synchronizing the high-frequency signal, but as I know it is proper for a periodic...
4. ### Studying Critique My Self-Study Schedule (Signal Processing & RF Electronics)

Hello everybody. I have already graduated I am currently in training at work which I am required to finish intensive courses. So I will start when it's completed. My interests are in Signal Processing & RF Electronics which you could tell by the study plan I created. I will be taking a slow...
5. ### Help with understanding of RF theory-Kinetic inductance parametric amp

So this might be long question that requires some literature review but I will try condense it as much as possible such that hopefully I can get some help without the reader having to review the related paper. So I will start off by saying that I am involved in a honours thesis in which I need...
6. ### High power RF amplifier at fixed frequency

Hello! I have a signal at fixed frequency of 4 MHz and amplitude of 0.075 V. I need to amplify it to ~75 V with the same frequency. I checked online a bit and I found either cheap amplifier that can't amplify this much, or very expensive ones that (almost) can (I might need to use a smaller...
7. ### Cost/Benefits of an RF Cavity vs Quartz Oscillator

I just encountered an RF cavity in the wild for the first time. It was used as the frequency reference in the Agilent 8640B RF signal generator, which I believe dates back to the 70's. Were quartz oscillators not an option back then? Or were they worse in stability back then? I'm curious about...
8. ### RF tube with photocathode, photoinjector

https://dspace.mit.edu/bitstream/handle/1721.1/95319/97ja001_full.pdf;sequence=1 In most (all?) RF tubes from klystron to magnetron to TWT and I assume also the gyrotron they use a DC accelerating field and a thermionic cathode with constant emission. The RF signal then gets introduced and it...
9. ### GPS receiver data transfer using RF transmission

Hi all I want to develop a miniature system using GPS receiver, a micro-controller, an RF transmitter and its receiver. The idea is to acquire lat/long of buoy dropped in sea which is equipped with miniature GPS receiver (with associated circuitry) which can send its position (lat/long data) to...
10. ### What does the RF waveform of wifi/bluetooth look like?

Homework Statement:: I tried google search and I give up. Relevant Equations:: How does output wave of wifi/bluetooth look like? How does output wave of wifi/bluetooth look like?
11. ### Explicit Calculation of Q Factor of Loaded Tuned Circuits

I would like to discuss in detail an interesting aspect dealing with general considerations and methods to calculate the Q factor of oscillating systems on the example of this regenerative receiver. Althought it is closely related to the discussion here discussion here (especially Baluncore's...
12. ### Impedance Matching when the Transmitter, Line and Load impedances are different

Assume we have a general rf system where source with impedance ##Z_S## transfers a signal to a load with impedance ##Z_L## through a transmission line with impedance ##Z_T##. We want to match this system in order to maximize it's effiency: In https://en.wikipedia.org/wiki/Impedance_matching...
13. ### RF Energy Harvesting Simulation

I want to do RF energy harvesting simulation for the measurement of Power Conversion Efficiency. So how can be simulation done on a single platform?. Kindly suggest
14. ### I Telescoping antenna -- why is there a knob on top?

This is probably a trivial or even a stupid question, the reason I am writing here is I couldn't find something satisfactory online. I am a new amateur radio operator. Currently enjoying listening to SW and MW bands. I have a nice radio receiver with a long telescopic antenna. I have noticed...
15. ### RF transmitter inside a metal enclosure, re. reflections

wavelength is .3 m to 6m, a 3m waveguide can do up to the 6m λ, so it will reflect all the frequencies concerned
16. ### RF Transistors, is there a 'minimum' frequency where they work?

Some RF transistors are not 'characterised' for lower frequencies, can they still be used? I get that a lower operating frequency (HF/1.8MHz) may not be the commercial target for an UHF transistor (>136MHz) so no effort spent on characterising them. Likewise HF transistors >1.8MHz not...
17. ### Can Two RF Signal Sources Connected in Parallel Increase Signal Amplitude?

Suppose I connect two identical signal generators to a dividing coaxial cable with two input ends and one output end. Is the signal amplitude from the output end the same as from one source, is it twice that or something in between? If this should be seen as analogous to two DC voltage sources...
18. ### What determines the frequency of an RF cavity?

I am reading a document describing RF cavities, in there it says that for the TM 010 mode cavities the frequency is only dependent on cavity radius but not length (which I assume is the length along the beam axis). Also I assume the TM 010 mode is the mode in which klystron cavities and particle...
19. ### Diffraction of RF - how is it affected by frequency?

I'm currently trying to get my head around the properties of UHF vs VHF propagation, specifically to do with diffraction around terrain and obstacles of various sizes (i.e buildings, vegetation etc). I understand from experience that UHF is generally more suitable in built up, urban...
20. ### Mosfet, Mesfet vs Bipolar transistors in RF circuits

I was wondering in general what types of semiconductors are used in most solid state RF power amplifiers like the ones at cell base stations and elsewhere. Do they use mosfets etc which can only switch a square waveform or are bipolar ones also used that can output sinusoidal outputs that can be...
21. ### RF shielding to keep signals inside

I may have blown a hole in my plot I can't sew back up. I need a way to shield RF emissions to keep them from escaping into the wilderness. It has to be impractical enough that it can only be implemented on a large scale such as a settlement, not on, say, a vessel.Core premises of the story: -...
22. ### Where is the demodulator in this AM receiver?

I am trying my hands on building receivers and transmitters. For now I would like to build this receiver here: now I see that the 500pH inductor in parallel witht he 200uH capacitor are in charge of filtering the unwanted frequencies. The top-left NPN is in my guess an emitter follower to...
23. ### Engineering How does this Bipolar RF Amplifier + Output Transformer circuit work?

I am trying to create a receiver for a personal project I am working on. This is the RF amplifier that I was given by a book I am following. How does this circuit work? Usually for a BJT amplifier I find the DC bias point and then use the small signal model after I bias the circuit? I understand...
24. ### Electrical RF conductivity of copper oxide

In my search, I have been looking for any data that might explain the RF resistance from 3 to 30 MHz range of the two basic types of copper oxides that form on the outside of bare copper wire. I believe these oxides become semiconductors and have large range of impedances. Due to the nature...
25. ### Basics of RF coil development for MRI

Hi all, I'm trying to understand basics of radiofrequency (RF) coil development for magnetic resonance imaging (MRI). For example, the problem is to develop simple surface single-loop RF coil tuned to 100 MHz. In program Coil32, I set the following parameters: diameter of the loop D = 20 mm...
26. ### Bias-Tee Design for an RF Circuit

Am having a difficult time with Bias-Tees. I do not know how to get the characteristic impedance (although I assume it uses the equation below) How would you use this if you are not given the R and the G? You could guess L and C. I know how Bias-Tees work and that a typical schematic would...
27. ### Why Doesn't Electron Shielding Block RF Radiation?

I am watching this video; at the 8:20 mark it shows that a proton in a magnetic field will align with the magnetic field very easily if there is no shielding from electrons, and therefore will require energy to shift to the opposite spin state; makes sense to me. I also understand that when...
28. ### Does Planck's relation apply to radio waves?

I have some doubts about whether Planck's relation (E=hf) applies to radio waves. This has been bugging me because trying to apply Planck's relation to radio frequency results in some inconsistencies that I've been unable to resolve. BTW, I have no physics training, so please go easy on me...
29. ### I How far away can 1KW of RF energy be detected?

Summary: If you put a parabolic antenna in space, haw far away could a signal be detected? If the size of an antenna and frequency were not limited, how far could a 1KW RFsignal be detected? Would it be under the -120dBm noise floor? In space does the noise floor go down? assuming also that...
30. ### A Does molybdenum react with an Argon plasma powered by RF power?

I'm thinking of implementing a metal disk-like probe in an Argon plasma which is powered by RF. Therefore I need to know a metal that's least reactive with the plasma. Does molybdenum meets this requirement?
31. ### Active power dissipated by a resistor from DC to RF

Hello all PF members! I was wondering about the power dissipated by resistor at high frequency which is: ##P=Re\left \{ U\cdot I^{*} \right \}=Re\left \{ \frac{\left |V^{+} \right |^{^{2}}}{2\left |Z_{c} \right |}\cdot (1-\left |\Gamma \right |^{2} )\right \}##, (1) where: ##Z_{c}## -...
32. ### RF Engineering Masters Degree | Distance Learning

Hello all, I've recently started working for a big defence company who are willing to send me on a Masters course and it would be most appropriate for me to find a course which focusses on RF/Wireless communications. I have a first class Honours degree in Electronic Systems Engineering from the...
33. ### RF cavity shunt impedance, PD and input power

I still did not understand this from my previous threads, what is the way to determine the instantaneous voltage across the cavity plates at any given moment, in a klystron I suppose the voltage would be proportional to the arriving electron bunch density which would determine the overall bunch...
34. ### How to build a Faraday cage to keep a WiFi signal inside?

I'm working on a wifi device testing box and made the first prototype of the Faraday cage. I need holes because of cooling. For this reason, the box has 3mm diameter holes on the top. The box made from steel, and have 2mm wall thickness. The wavelength around 12,5 cm for 2,4 GHz and 6 cm for...
35. ### Electronics Transmit RF signals directly to receiver in line of sight

Hello, I am trying to transmit radio signals across a distance of just under 1km to the receiver. The receiver is in line of sight with the transmitter. I just need to send the data in the most direct way possible, almost like shining a laser through the air. I was wondering what type of antenna...
36. ### Home Brew RF dummy load showing reactance at higher frequencies

I searched for dummy loads and found nothing on point. If there is and I missed it I apologize. If this is not correct section let me know and I will re-post. We need a high power dummy load in the 4kw range. for the amateur hf bands. The oil cooled "cantenna" type are at the most 1.5 kw...
37. ### RF pulse detection with Power Detectors

How can I use power detectors for RF pulse detection? RF pulse has a symmetric Gaussian-like shape. Is the output of power detectors continuous line or point?
38. ### RF cavities and related devices

Notice: I was told to make my own thread about the subject so here it is., please move it to a better subforum if there is a better place for it.At first I would like to ask three questions. 1) A torus shaped resonant cavity, like the ones found in particle accelerators and klystrons, is it a...
39. ### Equivalent circuit of the waveguide application problem

Hello! I'm trying to simulate a connection between two 2-port devices via waveguide but calculated results do not agree with those, calculated in simulation software. All calculations are in the notebooks. I took a two-port device and compared its S11 characteristic calculated using equivalent...
40. ### Electronics Synchronizing two devices with an RF signal

I need two synchronously flashing LEDS (as if they were connected together), but if possible I prefer to avoid connecting them with a wire. No problem with each one having its own battery and a driver. They will be about 2m apart without anything that could stop RF in between. I find it hard to...
41. ### RF Power Meter / SWR Meter Equivalent Circuit

I'm starting to get into RF electronics, and an upcoming project involves the use of a power meter / SWR meter. How do we model a power meter in terms of an equivalent circuit? i.e. is it just another impedance? or a transformer? or does it not effect the circuit at all, so we just don't include...
42. ### How is impedance matched with RF connectors?

I am just a bit confused as to how impedance is matched with RF connectors such as type-N or BNC connectors. I know Coaxial cabling and RF connectors come in common impedance ratings like 50 or 75 ohm but how is this all matched properly? For example many people have told me that when using...
43. ### Hello, I with this circuit, an RF oscillator

Hello, Can somebody help, to understand the transistor, what does do 390pF and C(tune), and 4,3µH, they form tank circiuits? and also resistor 1K and capacitor .1, is possible somebody with little words to descirbe how it works please... Thanks.
44. ### RF and MW receivers' sensitivity

I'm currently working on a novel RF and MW sensor and I wanted to know whether there is a paper that shows the current very best receiver sensitivity for a range of wavelengths in the RF-MW range in dBm preferably so I can directly compare to my device.
45. ### RF Tuner: Adjacent Channel Interference Rejection Filters

Hi guys The IF section of both monochrome and colour receivers must include rejection filters to suppress adjacent channel interference... Why exactly so, since the work of rf tuner in television receiver is to select a particular channel and as the required channel is selected it then passes...
46. ### Do rare earth magnets interfere with RF?

Im a bit of a physics newb so bare with me. I am designing a product that uses rare Earth magnets as a mounting solution for radar detectors and wanted to know if these magnets would somehow interfere with the performance of the radar detector? The magnets will not be mounted to the detector...
47. ### Power Ratings of RF Amplifiers

Hi all I am studying RF amplifiers data sheets and there is some confusion i am facing in its specifications. One such amplifier claims Power Output at 50 ohm load with 20% duty cycle to be 2 KW. However, the minimum gain it specifies is 63 dB and maximum input it claims to be 10 dBm (around...
48. ### Contrail Cirrus RF: Matt's Journey to Understand the Science

'HI, I'm Matt :) I'm unsure if I'm in the right place to be asking contrail-cirrus related questions and about the science behind it as I've had no science-based education since high-school [I'm 35]. I have had a keen interest and passion wanting to learn and understand all of the sciences...
49. ### Field Strength Calculation for an RF Emitter at Varying Distances

If an RF emitter is allowed to produce a field of 25uV/m @ 300 meters distance, how big will the field be at 3 meters? I'm guessing it's a hundred times stronger (2.5mV/m?) but does the 900 MHz frequency of the carrier come into play?
50. ### Counting clicks (signals) at a radio frequency receoved by a shortwave radio

Hello. I'm an English language teacher researching the details of a class project; I use projects to develop language skills. I have a background in mechanical engineering but know little to nothing of electrical engineering, hence this post. Questions for members of this forum: Electrical...