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.
-1
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1answer
51 views
H.D. T.V. reception very sensitive to light switch [closed]
I have an RCA hi-def rear projection television set, about 12 years old, that I use to snag ordinary over-the-air stations. No problem. Except that whenever a light switch is turned on or off, or when ...
1
vote
2answers
76 views
How does this circuit multiplex an antenna between a transmitter and receiver?
I've built a Softrock RXTX kit (full schematic: pdf gif, see lower-left corner). It has one connector for one antenna used for both receive and transmit, but I don't fully understand (likely due to my ...
1
vote
1answer
47 views
Accurately measure relative intensity noise (RIN) using RF spectral analyzer?
I'm trying to measure the relative intensity noise (RIN) of a laser using an RF spectrum analyser. It's a fairly common method (outline: ...
0
votes
1answer
21 views
xbee and interoperability
i'm studying interoperability in the telecommunication field and i want to know we must do what to have an xbee module interoperable with other zigbee devices of other manufacturers (not Digi). I ...
3
votes
2answers
99 views
How good is coaxial cable?
My question relates to the accumulated AC voltage that will appear on the screen of a length of coax:
If the cable is properly terminated at one end and fed with data (or any signal) at the other ...
0
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0answers
135 views
Would a 28ghz signal travel through a wall?
http://www.telegraph.co.uk/technology/samsung/10053221/Samsung-claims-5G-breakthrough.html
Samsung claimed to have invented a way to send high speed data at 28Ghz. I can believe it with a clear view ...
0
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1answer
38 views
The Conjugate Match
I've been deriving transmission line theory from scratch, out of curiosity, and I'm a bit hung up on one seemingly insignificant point.
When determining the real power drop on a reactive load with a ...
3
votes
2answers
78 views
Developing for TI's CC430F5137 MCU
I'm developing an embedded systems project (I'm quite new to the area) and I have determined that I want to use the CC430F5137, my problem is: How can I develop for it?
From cross-compilation, to ...
2
votes
2answers
192 views
Long Range RF communication
After playing with Arduino and different kind of sensors for my garden, now I'm starting a new project for my free time.
I want to work with RF communications because I need a long range device for ...
9
votes
4answers
186 views
Why can a feedline be cut randomly when the antenna needs a specific length?
With a mobile two-way radio you have the radio, an antenna mount kit and the actual whip antenna.
The antenna needs to be trimed to the correct length so to match the freequency you are Tx/Rx on.
...
-1
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0answers
40 views
Frequency meter application
Has anyone tried to implement a frequency counter with a maximum frequency of 50 Mhz on the beagle bone? I need to incorporate such a counter in my application.
2
votes
1answer
55 views
Detached antenna and connecting wire length
Since my this particular question didn't get any answer, I thought of asking a more focused question, along a path which seems a bit more feasible after few tests.
Is it possible to install the ...
2
votes
2answers
89 views
What are SMA connectors and what are they used for?
I have come across these rather big connectors on Altera trasciever boards in particular. I was wondering what is special about them.
2
votes
1answer
141 views
Can enough RF power melt an antenna?
I've heard of someone getting RF burns by touching a high power antenna. If enough power is supplied to the antenna could it melt, or would anything else happen? If so, how much power would have to be ...
2
votes
0answers
63 views
Wireless water level sensor, in sump. Installation best-practices for longivity
My wireless water-level sensor is working fine, and when deployed in the sump-well, it is giving me periodic readings quite well. At this stage, I have the circuit still on a breadboard, and now plan ...
-5
votes
0answers
54 views
How to connect a CAN transceiver to a microcontroller and then to an RF module? [closed]
I'm doing an RF interface between a computer and a CAN bus network. I'm using a CAN transceiver, a microcontroller (ATmega32C1 Automotive) with CAN protocol, and an RF module.
I'm stuck at the ...
-5
votes
2answers
81 views
What is the range of a 2dB usb wifi dongle? [closed]
For a home robotics project I need to connect my laptop to my robot's Raspberry Pi using wifi. For this to work I want to buy a simple usb wifi adapter to plug into my Raspi. I will need a range of ...
-7
votes
1answer
92 views
Creating custom frequency [closed]
I am working on building a 134 khz transmitter with range of 3 miles. I'm foggy on the calculation for capacitor vx resistance and transistors that will create this frequency. Any help would be ...
1
vote
2answers
71 views
Source of electromagnetic signal in kHz regime
I was wondering what emits electromagnetic signals in the kHz regime? When I touch the inner pin of an BNC cable connected to an oscilloscope, I see a large sinusoidal signal with ca 40 kHz.
0
votes
0answers
88 views
RF Link with APC220 between two PIC16F877's
I am attempting to communicate through a RF link between two PIC16F877's using APC220 Radio Transients. When the PIC UART's are connected with wires between TX and RX they communicate just fine, but ...
0
votes
1answer
37 views
antenna multicoupling connecting lines
I'm trying to find information about how to properly calculate the connecting coax length in a string of cavity filters for a VHF multicoupler. I figure it should be something like a 1/4 wave length ...
2
votes
4answers
141 views
Troubleshoot Crystal Radio
Alright, I'm totally confused. I have built the following circuit with absolutely no result, not even a click. Even after reading through several other similar questions on the board, I haven't ...
3
votes
3answers
106 views
Radio wave transmission and receiving antenna
When you transmit signals at radio frequency why are the antennas open ended (open circuit)? I can understand that changing the electric field causes changes in the magnetic field and hence the wave ...
0
votes
1answer
70 views
What determines how narrow a radio channel can be?
As an example: We used to have analog TV broadcast but now we're switched to digital. With digital we're able to pack in more data into a smaller frequency range. I assume that it is our advancements ...
5
votes
4answers
147 views
How do arcs generate radio-frequency
When I have an electric arc, and put an AM radio nearby, I hear a crackle and the station that I previously heard goes away. I am wondering what is going on with the electricity through the air to ...
2
votes
2answers
116 views
Coaxial cable theory
Well I was learning transmission but I got a bit confused when I came to coaxial cables transmission at radio frequency.
What I am lost is how the waves are propagating in the cable, I was thinking ...
0
votes
2answers
65 views
OOC coding in Wireless Radio Mesh Network
Can anyone explain me whether OOC (i.e. optical orthogonal coding) works in radio frequency? Or only for optical/laser technology?
4
votes
5answers
143 views
Are E and B fields in phase in electromagnetic radiation?
I recently wrote this answer, in which I said:
Radio waves are electromagnetic radiation. Electromagnetic radiation contains of two components, one electrical and one magnetic. These components ...
5
votes
5answers
185 views
What is the difference between electromagnetism and electromagnetic radiation?
In a previous question, I asked if having 2 coils of wire with electricity flowing from one to the other is RF, and they replied that it was not Radio Frequency. I was puzzled because I thought this ...
1
vote
2answers
183 views
Simple Morse code transceiver circuit
I want to build a portable device (handheld) that receives and transmits Morse code in the form of Radio Frequency. I want the antenna length to be 8 inches or less and would also like a range of up ...
1
vote
1answer
55 views
ZigBee module compatibility
Are the XBee series 2 modules from Digi compatible with other brands complying with the ZigBee standard?
0
votes
2answers
101 views
Can the antenna of a Wi-Fi modem pick up a cell phone's MIN or ESN?
Specifically: Can the antenna of a Wi-Fi modem pick up a cell phone's broadcast of its mobile identification number (MIN) and electronic serial number (ESN)?
Generally: We are trying to determine ...
3
votes
1answer
148 views
Is sending a signal over 433.92 Mhz blocked by plastic?
to be honoust: I never understood radiowaves; how I can receive radio in my house? Transferring a complete video through air from laptop to router? Never a clue.
So with that (lack of) knowledge my ...
3
votes
3answers
202 views
RF Design: A Bluetooth Repeater
I am currently stumped in the design process in creating a method to intercept Bluetooth signals with an antenna and simply outputting the exact signal through another antenna.
Some Background
I ...
10
votes
1answer
216 views
GPS Design Review (RF Input)
I've designed a PCB in Eagle to host a GPS Receiver module and a GPS patch antenna. The RF input to the module is specified as a 50Ω unbalanced (coaxial) RF input. I used this calculator to calculate ...
2
votes
4answers
154 views
Measuring Signal Strength with a RF Circuit
Note: I'm primarly a 4th year Computer Science student, but I have also interest in electronics but I have very limited knowlege.
Is it possible to measure the signal quality or level of a RF ...
1
vote
4answers
130 views
Radio Waves reach in function of frequency
What is the relationship between the reach of a RF signal and its frequency?
What I mean is: If power is kept constant, should I use high or low frequency waves to get a better reach? Why?
1
vote
2answers
93 views
Dipole antenna length calculation — why so much variation?
Was checking few online calculators for dipole antenna length computation, and found that each tool, gave a different length. Is dipole construction based purely on heuristics, or is there some sound ...
1
vote
3answers
134 views
Stereo AM/FM Concept?
There are tons of schematics and concepts online of AM or FM transmitters. I wish to build one using discrete components (at most an op-amp).
The problem is, how would transmission of stereo work? In ...
1
vote
0answers
74 views
Why does my bluetooth dongle use more current when paired then when idle?
I have a bluetooth dongle which is connected through USB to my PC. I wanted to measure the current drawn and hence I connected an ammeter in series with the 5V line and am measuring the current. I ...
1
vote
2answers
125 views
180 Phase shift for oscillator
I am currently learning how to design/build a crystal radio receiver, transmitter and have a question for the 180 degrees phase shift for the carrier amplifier/oscillator system.
I commonly see this ...
6
votes
3answers
209 views
What's the best/easiest way to measure an unkown inductance without an RLC meter?
Is there a decent way to measure inductance accurately using an oscope and a function generator? The best method I can find is to build a tank circuit and sweep the frequency until the highest voltage ...
4
votes
1answer
114 views
DIY Inductor: Solve for number of turns without knowing the length?
I'm trying to wrap my own inductors (air coil) for an RF circuit that I am making and I am having a little trouble solving for the number of turns I need to reach the desired inductance.
...
3
votes
2answers
91 views
UHF Phase Modulation
I would like to design a system that produces -10 degrees and +10 degrees phase shifts at 409.6MHz (Basically BPSK).
The way I'm thinking about approaching this is by using a DDS to generate the BPSK ...
2
votes
1answer
65 views
What is the commonality between a radio, a welding power source and an induction heater?
I was reading into the basics of welding power supply (because I have taken up TIG welding) and inductive heating (because it is part of a number of applications in metal fabrication), and I noticed ...
2
votes
2answers
78 views
Groundplanes for Wideband synthesizer
I'm build a synthesizer (up to 2GHz) and got a questions regarding the gound planes (analog vs. digital).
According to the datasheet (p. 7) some pins must be connected to analog GND, ex. pin 10 must ...
2
votes
1answer
147 views
FM Quadrature detector - is it the best choice
My input is an FM carrier of 80.00MHz. It is FM modulated with 625kbpsec data. The deviation from carrier is about +/-700kHz. The data never spends more than about 38us in a low state or high state ...
0
votes
1answer
114 views
Do I need FCC certification to sell if my device uses ISM bands?
I have made a portable xbee-like transceiver. The system will be operating at 2.44000GHz (RX) and 2.46000GHz (TX). The TX power to the antenna is well underneath +30dBm; the EIRP is also less than ...
3
votes
1answer
56 views
Using low-noise amplifiers
I have a receiver with sensitivity -50 dBm and an input signal from an antenna of -90 dBm, is it prudent to amplify the signal with a cascade of low-noise amplifiers? The LNA I found for my frequency ...
2
votes
2answers
113 views
Is there any circuit like “Burglar alarm ” or “Proximity dector” with a range of 100 meters
I am in search of a circuit which works with
IR or RF wave with a range of 100 meter to detect proximity or burglar.
I need this to detect the presence of human or animals
One thing important is i ...
