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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48 views

how to avoid interference in 433MHZ rf transmission (in my case)

I suppose to do RKE (remote keyless entry) for door opening as a commercial product, there is DC motor which drive the door to open or close (receiver side), on transmitter side (remote) three button ...
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7answers
208 views
+50

How can I amplify my transmitter's RF signal to open the garage from the 12th floor?

I live on the 12th floor of my apartment building and the garage door is on the ground level right below me but is obstructed by trees and a ledge. I do not have line of sight. My garage door ...
35
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9answers
4k views

Can a radio transmitter somehow detect the number of receivers in its area?

During conversation, a colleague proposed that over-the-air television and radio broadcasters can determine the number of viewers or listeners based on the "load" on their signal. This seems to me ...
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1answer
46 views

Embedded microstrip antenna

How well known are embedded microstrip antennas in general and are they feasible. I want to pot a 2.4 Ghz antenna for product reliability/water and shock proof reasons, but finding information and ...
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0answers
19 views

RF 433MHz - RXB12 vs XY-MK-5V

Anybody knows the difference between these RF receivers? I have a project and I am not able to work with RXB12. It is not receiving my transmitter.
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1answer
17 views

ETSI Tx Power standard for short Range Devices. I am Confused

I came across the European Telecommunication Standards Institute (ETSI) standard for non specific Short Range Devices which is documented in EN 300.200 . On page 28 under Section 7.2.3 with Heading ...
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0answers
46 views

How to choosing the right transistors for active antennas

I'm trying to build a Mini Whip active antenna that receives 10KHz to 20MHz. But I'm having trouble finding the right components especially the transistors. It calls for a J310 and a 2N5109, which ...
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1answer
31 views

How to build a transmitter using a VCO module

this question is the consequence of my previous questions, since I am learning how RF transmitters works. In past I have also built some oscillators (using little transistors and a bunch of ...
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2answers
50 views

Make an RF transmitter: classic transistor oscillator or VCO module?

This question is about pros and cons of making an RF transmitter (eg in the FM band) in the classical way (eg. with a "transistor based" oscillator circuit, like this one which is very classic and ...
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2answers
63 views

How can current flow in dipole antennas when there is no potential across them?

I have been trying to understand antennas and I've been trying to analyze how the transmitter's energy is transferred. It is clear that for current to flow there must exist a potential difference ...
4
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0answers
47 views

ISM band rules for spread-spectrum: how much do I need to spread?

I'm doing a preliminary study for a 5.8 GHz ISM band data downlink for a cube satellite. I know that spread-spectrum is mandatory for ISM, but the FCC rules seem pretty opaque on how much I need to ...
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2answers
69 views

RF Transmit Power in an ISM band

I was browsing through some OFCOM Frequency Allocation Tables for use on a small project I'm doing. I require the use of some unlicensed ISM bands in the UK, and found that the lowest unlicensed band ...
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2answers
49 views

RF power limiter

I am interested in constructing my own version of an RF power limiter. There exist models such as the 11930A Power Limiter, but are very expensive. The intended use for the device is to limit input ...
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1answer
55 views

How can you design a frequency divider circuit?

I have been trying to design a frequency multiplier circuit which can translate frequencies from Mhz range to a few Ghz range using PLL. But I am not able to figure out how to create the frequency ...
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1answer
35 views

Signal Detector (Field Strength Meter)

Hello I have attached a circuit of a Field Strength Meter that I came up with, my target frequency is around 500Mhz. I was wondering if a design like this will even be able to tune to 500Mhz. I am ...
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1answer
30 views

Radio Control car telemetry

I am trying to get some input on the feasibility of this project. I will have a radio controlled car. The car will have sensors that will output data like acceleration, gyro something like 6DOF. A ...
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0answers
33 views

100m Bluetooth Range

Is it possible to get 100m of Bluetooth range with a meandering antenna and 10dBm transmit power? I'm using a CSR chip and it's interally limited to 10dBm and won't allow 20dBm. If it's not ...
12
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1answer
1k views

Why is 433 MHz used widely in RF modules?

I was planning to interface an RF module to my PIC16F877A microcontroller and was exploring the web. I came across many modules which use 433 MHz as the standard frequency. Why is it so? Can't we ...
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0answers
25 views

Transformer characteristic for impedance matching in RF

In an rf impedance matching circuit it is assumed that transformer is ideal or large enough. I just wanted to know the quantification of "large enough" (which parameter is large with respect to what)
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1answer
82 views

radio energy harvesting on WIFI questions

I am building up a radio harvesting circuit on WIFI signal, but I fail. Actually I am very new to antenna and RF aspects.I have several questions about the circuit. First of all, I follow this ...
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1answer
61 views

Signal Detector (UHF Field Strength Meter)

after some reading I ended up finding a relatively basic FSM, using a antenna, an LC circuit to tune to a specific frequency, and a RF diode and final a ammeter to measure signal strength. My target ...
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0answers
31 views

nrf24l01+ transmit wrong values, solution and question

I have 2 AtMega328p with NRF, one is tx, one is rx. I disabled auto ACK, CRC, IRQ pin, and Dynamic payload. Set the PA to MAX (0dbm), payload to 4 Bytes, Channel to 0x02, and the data rate to 1MBPS. ...
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0answers
18 views

Single ended FET mixer matching section design

I am designing a single ended FET mixer using atf21170 and I have isolated the RF and LO port by a bandpass filter,at the output I am using a 6th order chebyshev low pass filter.The major problem ...
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2answers
68 views

Is it possible to measure a 433MHz RF Transceiver signal using a 100MHz Oscilloscope? At least to see if it is transmitting or not

I'm generating a serial signal and feeding it to a 433MHz RF Transceiver and I want to know if the signal is at least being transported before I starting working on the receiving end.
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1answer
57 views

Garage key frequency and baud rate [closed]

1) What means baud rate in garage door keys? Is it a waiting period between each byte sent? (I am talking about OOK keys). And can i just sent all the byes without wait? 2) What all baud rates are ...
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0answers
35 views

RF frequency synthesis - how low power can I reasonably go?

I'm an undergrad working on the analog frontend for a student-developed cube satellite. After looking at the options, I've decided to use the CML Microcircuits CMX994 for the receiver and the CMX998 ...
-2
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0answers
35 views

Frequency presence to light up LED

Can anyone provide a simple circuit schematic that uses an antenna to detect the presence of a specific frequency and in response lights up an LED. I have been doing some reading on resonant (LC) ...
2
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0answers
61 views

Specified frequency signal detector

I understand that band pass filters are used in some circuits to filter out the desired frequencies. I also understand that an antenna picks up radio waves in the air and converts it into electrical ...
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2answers
74 views

Trouble tuning am radio

I have been following the tutorial below to build an AM radio, and when powered on I was picking up what id presume to be radio waves (what I'd describe as a mishmash of "whooshing" sporadic ...
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2answers
74 views

Create a rolling code garage door opener [closed]

I've been tinkering with my Raspberry Pi lately and I've been looking at opening garage doors. A majority of garage doors have the ability to "learn" a new remote. Is it possible to program a Pi with ...
-2
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0answers
16 views

Variation in mixer conversion gain

I have designed a mixer using NE25139 and I am noticing a gain increase of 0.2db as i increase LO power from 0dBm to 6dBm.Why does it happen so?
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1answer
43 views

What is my best possible antenna setup for a 900MHz 24dBm XBee?

I have two of these 24dBm XBee modules in a semi-LOS setup (1 receiver will be on the ground, obscurred by some tents/structures and other Burning Man camp crap), with these supposedly 3dBi antennas ...
2
votes
1answer
52 views

Don't RF devices need to be shielded to pass FCC?

I'm looking at this device. Internally, the Bluetooth chip isn't shielded but it still seems to have passed FCC. Addition to that, there was no Modular Approval Request Letter, which typically ...
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0answers
31 views

Cell phone bluetooth range

I've got this phone I'm doing some range testing with...Namely, a Samsung S5 with the latest firmware and I'm testing the WLAN/Bluetooth radio. This phone has unbelievable range...but, when I replace ...
2
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1answer
36 views

Where to Measure S11 with a VNA

I have someone else's design that I have been asked to choose matching components for. The antenna is a chip antenna and the filter is a band pass SAW filter in a single package. The SAW filter is ...
0
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0answers
40 views

wireless on/off switch for LED using RF transmitter reciever

i wanted to switch on an LED using an RF transmitter receiver like we can see in this video (https://www.youtube.com/watch?v=jeRtyOgf0mI), although i do not want the morse code application, i just ...
0
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1answer
55 views

Create a new wireless protocol for industrial

I'm working on project that lets industrial machines communicate to each other wirelessly. It seems that Zigbee at 868MHz is the best choice (if you have any other suggestion it would be great), ...
0
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1answer
59 views

2.4GHz signal through 900MHz amplifier?

Nobbie question, but I was wondering: if I were to generate 2400MHz signal in VCO and put it through, let's say 900MHz RF amplifier, will the output signal be 900MHz? Or would this experiment fry the ...
0
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0answers
50 views

Reason for radio device functioning only when connected with cables between connectors

I have a prototyped board with a 2x4 female connector which is supposed to connect to a NRF24L01+. If I plug it in directly it's not working, however if I connect cables between them everything is ...
1
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1answer
59 views

Difference between antenna resistance and impedance

From what I understand about antennas, they have a certain impedance. At the antenna's resonant frequency, the capacitive and inductive reactances cancel and the reactive part of the antenna ...
1
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1answer
54 views

Is it possible to capture a 433MHz RF signal using the PC bluetooth?

I'm student working on a project at my university where I have to transmit a signal that I'm generating with a micro controller using a SmartALPHA RF Transceiver with a 433MHz signal. I have to ...
1
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0answers
19 views

Advice on Coplanar Waveguide and Ground layout of Antenna

I've this antenna model AH316M245001-T. Datasheet: http://www.mouser.com/ds/2/396/chipantenna01_e-587795.pdf RF signal will be routed using CPW with ground vias. RF freq. is 2.4Ghz, 50ohm line. I ...
0
votes
0answers
33 views

MESFET Bias at high frequencies

I am using NE25139 as a mixer.First I want to ask why for such high frequency devices the output curves of drain current vs drain to source voltage are not specified.Then how can I select my values ...
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1answer
78 views

Where does the oscillator frequency come from?

In case of a power amplifier I know the power comes from dc supply so it wouldn't be too strange to question where does the frequency in an oscillator comes from? This question actually came to my ...
0
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1answer
56 views

Dual gate fet mixer design problem

1-I have designed an LNA amplifier at 5.5 GHz and a Dielectric Resonator at 5GHz.I was hoping to down convert the LNA output using a dual gate mixer (5.5GHz at RF and 5GHz at LO) but none of the dual ...
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1answer
85 views

wireless device to send data with low latency up to 1km

I need a device about the size of a phone with 2 buttons, the device will be used to let a server know the outcome of an event (2 possible outcomes). A mobile phone app would be the obvious choice but ...
0
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0answers
23 views

Can I interlink several RF transmitters and receivers?

Complete electronics novice here. I am trying to figure it if an idea is plausible. I want to know if I can have several small rf transmitters and receivers, each receiver capable of recognizing all ...
2
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0answers
24 views

Is GNSS S/N equivalent to C/N?

I work in developing software that integrates with GPS receivers. I've struggled for years with inconsistencies in documentation for the NMEA emitted by such receivers, and I've decided to put it to ...
2
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1answer
110 views

Determining an aproximate position through triangulation

Disclaimer: I'm relatively new to electronics (although not to programming) so please excuse my ignorance. First of all I should state that I'm aware there are already multiple, well answered posts ...
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0answers
24 views

Return Loss \$ (S_{11} ) \$ Equation for a nth-order Chebyshev Type 2 Filter [duplicate]

I need an closed form equation for the return loss \$ S_{11} \$ of an n-th order Chebyshev Type 2 low-pass prototype filter. I am designing a high power RF (lumped element) n-th order Chebyshev Type ...