Short for Radio-Frequency. Frequencies at which radiation (intentional or not) plays a role. Typically associated with wireless communications, but also relevant for high-speed PCB design.
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Why are RF transistors so expensive?
I was looking around for RF power transistors expecting them to have around the same price as the IRFP250 and I noticed the immense price. A 160 watt UHF dual MOSFET was 70$. What characteristics make ...
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66 views
RF question: Panel antenna for satellite communication
Would a "panel antenna" used for RFID (probably microstrip-based; e.g. http://www.joymax.com.tw/index.php?_Page=product&mode=show&cid=2387&pid=364) work for satellite communication, ...
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131 views
Is this an SMA female connector?
Can anyone identify this coax connector? I think it might be an SMA female connector but I'm no expert. It has threads on the outside and a hole inside. The diameter (to the outside of the threads) ...
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76 views
Is this an SMC connector?
Can anyone identify this tiny connector? The tape measure is in inches. The connector has threads on the outside and a pin inside. The diameter is about 1/16th of an inch. I think it might be an ...
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2answers
79 views
How do I properly clean oscilloscope BNC connectors?
Over time with use BNC connectors on test equipment will attract contaminants . Since BNC is usually used for relatively high frequencies, I suspect that contaminants will have negatively affect ...
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139 views
Why do cables that carry RF have 2 leads
I just got a ham radio license, and I am trying to figure out the mystery of RF.
From the output on your transceiver to an antenna or an RF amp, there is a 2 lead coax cable. If antennas only have ...
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66 views
RF power envelope
If I have an oscillator at 10 kHz outputting 5 W, using AM, like this.
Where does the power in the sidebands come from?
Is the power the result of the harmonic relationship between the carrier and ...
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150 views
Why the conversion to Intermediate Frequency?
While studying about various communication systems (Superheterodyne receivers and Television receivers, to name a few) I often come across blocks that convert RF signals to Intermediate Frequency (IF) ...
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113 views
Does an antenna's radiation pattern characterize its ability as a receiver?
In other words, would a directional antenna used as a receiver be more sensitive to signals coming from one direction, or be equally sensitive to signals from all directions?
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42 views
Regarding Radio Frequency (RF) when a Receiver/Antenna Setup can receive DC - What Exactly Does that (DC) Mean?
I do not have a strong foundation in RF. I have been doing some research but I still do not properly grasp what it means if a receiver/antenna can do DC to X Hz. For example this Funcube Upconverter, ...
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68 views
How do you determine antenna gain from a polar radiation plot?
Using the plot from the Wikipedia Patch antenna page as an example, how is the 9dBi value obtained? It looks like the radiation is barely higher than 0dBi at the strongest location.
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46 views
When talking about antenna gain (dBi), is the largest gain implied?
Since shouldn't dBi gain vary depending on radial location?
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90 views
Cheap easy way to test for RF power output
I have a need to remotely confirm output power on a radio. However I'm poor and want to do cheaply.
All I need is a confirmation that it's pumping out in excess of 75 Watts and then have a contact ...
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113 views
Analyze My Homebrew Diplexer
I'm in need of a diplexer that'll separate RF signals from a single feedline to two antennas. What I designed and built was a diplexer that would allow ~38 Mhz and below out port 1, with ~38 MHz and ...
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101 views
I would like to light a very tiny light (led?) using RF
I would like to light something very tiny like these hobbylinc.com/model_railroad_light_bulbs without running wires for my wife's dollhouses. I was thinking RF to power them. The houses are VERY ...
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1answer
96 views
How can I tell if an RF transmitter is transmitting?
In my project, I use a use an RF Transmitter and Receiver. One of the RF components seemed to fail because the connection between my Arduinos no longer works. I cannot determine whether the RF ...
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2answers
87 views
terminated cable capacitance
As much as I know, the input impedance of a coaxial cable with a characteristic impedance of 50 \$\Omega\$ which is terminated with a 50 \$\Omega\$ load resistor, should be 50 \$\Omega\$ as well. This ...
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63 views
Using Titanium as antenna in implantable tracking system
I have some question regarding using titanium as antenna. I have to think about an implantable tracking system for animals. One of the requirements is that it should be as small as possible. Other ...
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2answers
124 views
How do IR rangefinders accomplish centimeter precision without high speed / high cost parts?
I'm currently working on a system that requires an RF rangefinder with ~15 cm precision, over a range of about 50 meters. My research into the field has shown that I'll need complex and expensive ...
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1answer
115 views
Music through RF
I have recently been fascinated with wireless-ness. I thought of a little project so I could do a little research in this area. This project uses a circuit board found in a Christmas card or birthday ...
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2answers
71 views
How are the positions of matching network elements determined for RF power amplifiers?
I asked an electrophysicist and he gave me a wishy washy experimental answer. Let me provide an example.
Let's say we want 50 ohm input and 50 ohm output from some particular wideband amplifier. The ...
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71 views
What is between oscillator and antenna for a simple carrier transmitter
I have a 20.000 Mhz Crystal Oscillator Module. If I just wanted to transmit a carrier wave at 20 megahertz, what would be from A to B?
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65 views
Using one RF transmitter to send an On/Off signal to multiple receivers
I want to create a system where I can send an On/Off signal to multiple receivers, to say, tell them to turn on an LED. Would I need to have a transmitter/receiver pair for each LED, or can I just ...
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17 views
How do I locate proper radio initialization procedure in order to send IEEE 802.15.4 frame?
I am using an AT86RF233 radio connected to an MSP 430 micro-controller.
I need to write a function similar to line 92 on this page. This function (trx_frame_write) is supposed write a frame for ...
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59 views
How to improve reception in a wireless CCTV system?
I have a 2.4Ghz wireless CCTV system just purchased for my barn. The system is a Uniden UDR444 with two cameras. The barn is 200' from the house, where I need to monitor the camerasin the barn. Uniden ...
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23 views
What does a preamble look like in the definition of an IEEE 802.15.4 frame?
If you look under the section "802.15.4 Frame Format" on this page you will see it defines
Preamble Sequence : 4 octets
Start Frame Delimiter (SFD) : 1 octet
...
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78 views
Measuring Power per Hertz of a RF signal
I am testing my communication application to see it's performance over different frequencies. So I need to measure power at different frequencies of operation. I have been told that my limitation for ...
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76 views
Relationship between FFT in dB and spectrum analyser output in dBm
I am trying to calibrate my RF daughter board in USRP software defined radio. I am trying to measure transmitted power for different frequencies at a certain set gain and transmitter amplitude. When I ...
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74 views
Amplifying the signal from a tranciever
I'm thinking of starting to play with some RF control for a project I'm working on (a multicopter). Due to the nature of this project I was looking into how to amplify the signal so to get a better ...
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135 views
What are these rectangular sidebands on my local FM radio station?
I recently bought an inexpensive USB software-defined radio dongle, and have been poking around my local spectrum:
The above image is one of the local FM radio stations (88.7 Mhz, to be specific). I ...
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2answers
108 views
What is the best way to debug a radio?
I am currently programming / configuring an Atmel AT86RF233 radio and trying to get it to communicate with an digi xbee. So far I have set the following fields on the Atmel radio:
extended address
...
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2answers
190 views
What is the importance of the \$50\Omega\$ resistors in this RF op-amp circuit?
From the TI application note RF and IF amplifiers with op amps:
The source says "The 39-pF capacitor provides peaking to compensate for some high-frequency roll-off, but better IP3 performance can ...
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83 views
What Modulation does weather radio use?
Here is the official site which says the frequency which weather radio broadcasts at (around 162 Mhz). The site doesn't say anything about modulation though. What modulation is used in this radio ...
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95 views
Why is receiver RSSI so much lower than the output power of a transmitter?
When we measure the output power of a small transmitter we might see something around 30 dBm (1W) but a receiver/WLAN card/UE ...
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55 views
How may I demonstrate the operation of an SWR meter?
I would like to demonstrate the principle of an SWR meter in a talk I am going to give to my local amateur radio club, using the basic "micromatch" circuit as in Bruene's article, which I found at:
...
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199 views
Measuring RF power of a communication signal
I am running a software radio application. I need to measure the power of transmitted ofdm signal. The issue is that FCC has regulations of -50dBm/Hz. So I understand that if i need to send a signal ...
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1answer
118 views
How to turn analog audio into AM/FM signal for radio receiver?
Because I have several good (but older) sound systems in my apartment I am looking for a way to play audio from an iPhone or computer (anything with a headphone jack) synchronously on all of them. All ...
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97 views
Antenna Parallel to High Voltage Line Has AC Current - Is It Acting as an Inductor?
I'm attempting to use one of the roofline gutters on my house as a "longwire" antenna. The center conductor of my coax cable connects to the gutter, the shield conductor to a grounding rod. The ...
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3answers
274 views
How to connect 20 wireless sensors in one receiver with arduino?
I live in a house with many doors and windows and I plan - as an easy project - to be able to detect and see which door/window is open using simple leds. What I do not want to do is to have 2 or 3 ...
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179 views
Why would I use a transformer instead of one inductor a crystal set?
I'm reading up on A Simple Radio Receiver. I have a question about this image:
The signal from the antenna (perhaps a few tens of microvolts, or hundreds for a nearby transmitting station) ...
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146 views
Does an RF receiver constantly consume power?
I'm building a battery operated robotic arm and would like to use a cheap, short distance RF transmitter/receiver kit to trigger it. However I would like to know whether the receiver will constantly ...
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3answers
132 views
Why is speech malformed when listening to a USB signal with an LSB receiver?
When you listen to an LSB (Lower Side Band) signal with your radio set to USB (Upper Side Band) or vice versa, the speech you hear is malformed. What causes this behaviour?
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131 views
Two signals alternately on the left and right of a frequency
I was listening to the WebSDR of Twente University, just outside the amateur band, and saw these signals. The x axis is frequency in kilohertz, the y axis is time, where the whole axis shown is about ...
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2answers
108 views
What is the bandwidth of an antenna ? and what happens when a narrow bandwidth is used?
I'm trying to understand the bandwidth of an antenna in order to choose the right one for my next project which involves a Nordic 2.4GHz radio transceiver (NRF24 series) that operates from 2400MHz to ...
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153 views
transmit data wirelessly under water?
I am looking into constructing a small submarine with a Raspberry Pi. This is just for a hobby project but my idea is to have it communicate with the surface wirelessly. I know that normal radio waves ...
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94 views
NRF24L01 presence detetion
I have adapted my RF73/RFM73 library for the NRF24L01. These chips are almost identical, except that the RFM73 has a second bank of registers that must be initialized with some magical values. The ...
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98 views
How can I find an AVR chip with built-in RF transceiver?
I'm going to build a couple of small devices that communicate wirelessly. To simplify construction, I've decided to look for a chip (preferrably on a breakout board) that combines a programmable ...
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523 views
What happens at the end of a transmission line?
Let's say I wanted to make a widget containing a relay to switch between two antennas. There is a coax transmission line coming in from the transmitter, and two going out, each to a separate antenna. ...
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85 views
The purpose of I and Q channels in RF communication
I have searched both dsp and electronics stack exchange but I remain confused about the reasons why information is sent in I/Q channels.
For a while, I thought that the main reason for sending I/Q ...
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52 views
Can RFID readers submit scanned data to one location?
Let's assume that I have lots of RFID readers, is there a way, either a specific product or peripheral that allows the reader to send data about the tag it scanned over a distance of about 500m - 650m ...
