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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ISM RF link problem

I've established an RF link using TWS-CS-2 as a transmitter and AM-HRR3-433 as a receiver. The carrier frequency : 433.92MHz. Modulation type : ASK. ATtiny25 to generate and decode Manchester ...
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38 views

I want to make an oscillator with 160 MHz

I want this for my project. So I have decided to make a basic Wien bridge oscillator. $$f = \frac{1}{2\pi R C}$$ So if I choose a capacitor of 0.1 nano farads and a resistor of 10 ohms, I should ...
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13 views

RF Solutions ZULU module

I am trying to set up a remote battery voltage checker that will radio the voltage read from the battery to a computer. I went for the ZULU module (by mistake as I should have brought the ZULU-M ...
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46 views

Does a 40 MHz radio frequency have any interference to Bluetooth signal?

From my understanding, the Bluetooth signal is using a 2.4 GHz frequency. However, when someone is playing with a 40 MHz RC vehicle, the Bluetooth signal keep on getting interrupted or disconnected. ...
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1answer
85 views

Help with a RF reciever circuit

Recently I have been working on a basic RF receiver, but my efforts so far have proved fruitless. I designed the following circuit based of of previous research into the topic. According to what I ...
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3answers
94 views

Impedance matching an RLC circuit (inductor macroscopically drawn on PCB)

Context: I am a physics grad student with basic knowledge of circuits, but impedance matching and RF domain are beyond my normal scope. My PCB is actually copper bonded to a ceramic substrate that is ...
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3answers
147 views

PCB RF Layout Critique: Input on my radio-telescope PCB

I'm attempting to do the board layout for a radio-telescope we're building at one of my jobs. Here is the overall system topology: QRFH is for "Quad Ridged Feed Horn". It's a rather esoteric ...
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2answers
41 views

RF remote with three buttons

I am trying to create an RF remote that has 6 buttons but the RF encoder only has 4 inputs. Is this possible and preferably I would not like to use a separate chip. This is what I am using: ...
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1answer
60 views

RF Harmonics and Spectrum Analysers

Please forgive the long question. I have split it into 2 parts. I am very confused about how harmonic suppression is measured in RF system (in my case, ham radios). I have picked up a couple of the ...
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2answers
50 views

How to make a RF Additive Mixer for two inputs in same frequency band?

One of the most common designs for a SSB modulator (phase shift method) involves an additive mixer as the very last stage. Here is a block diagram for reference: This additive mixer must provide ...
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32 views

Tablet radiation (RF vs EMF ) [closed]

I own a tablet without 3G/phone functionality but equipped with Wi-fi There is a lot of mixing up RF (radio frequency) with EMF (electric magnetic field) when looking for health issues arising from ...
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1answer
61 views

USB to RF bridge: Kettler Ergorace bike

I own a Kettler Ergorace indoor bike. It's possible to create exercises using the USB interface. When plugged into a PC, it is shown as a virtual com port (SiLabs CP2102) I would like to control it ...
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54 views

Determine the working frequency band of unknown RFID chip

I have a passive RFID chip from which I would like to scan the ID. I have a standard USB RFID Reader, but this doesnt print out anything. This reader scans the 120–150 kHz range, so the chip must ...
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1answer
38 views

Radio direction finding - dependence on source signal type

I want to make a robot that can track the direction of the transmitter that is controlling it, for example to aim a camera at the transmitter. The robot vehicle will be controlled by a 2.4ghz ...
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1answer
90 views

Arduino 433MHz transmission fails if falling edge is less than 122ms

I am trying to control a LED using a high-power 433MHz transmitter receiver pair, with transmitter connected to my Arduino Nano. Here is the transmitter (XLPCF20): ...
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1answer
43 views

FM Transmitter Amplifier — Maximum output power with non-customized parts?

I would like to build an FM transmitter on my own and I found a nice circuit that acts as a USB sound card to transmit low power FM signals. http://tipok.org.ua/node/35 My plan is to add another ...
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33 views

How to convert square output of Si5351 to sawtooth when working at 28.8 MHz

I'm going to build a clock generator around the Si5351A chip. The configured output frequency will be 28.8 MHz. The output of the chip can only be a square wave. I've seen some schematics on the web ...
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1answer
515 views

What does this symbol in the schematic represent?

I know the symbol at the bottom is ground, but I can't get what the other symbol is. It can be a single symbol of two arrows pointing at each other, or two symbols each one a arrow. I also have the ...
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7answers
283 views

Measuring direction of object (or angle of signal origin)

I am interested in somehow tracking the "compass" direction of a moving object from a reference-station -- in other words, something similar to submarine sonar systems (although I'm unsure how those ...
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1answer
37 views

Colpitts VCO by varying base voltage

I've noticed that if I build a Colpitts oscillator (audio range) using a transistor in the common base configuration (similar to the circuit here) I can vary the voltage on the base and get a wide ...
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1answer
65 views

Two arduino unit communication

OK plain and simple I'm not sure to use IR or RF. This is short distance up to maybe 10 ft. I have an Arduino Uno that I have all set up here. I press a button and it carries out its code. This is ...
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2answers
787 views

868 MHz frequency standard

I am wondering whether I am free to use any transmit/receive methods on this particular frequency or do I need to stick to some standards. I am willing to buy a chip with PHY layer of 868 MHz and we ...
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1answer
73 views

What exactly is (Horn) Antenna Gain

I was doing an experiment for finding the radiation pattern of Pyramidal Horn Antennas at RF frequencies(as part of my course curriculum). There I came across the Friis Transmission Equation What ...
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5answers
602 views

What are these metal plates covering parts of PCBs called?

I am trying to mod my wireless router, but one of the parts is under a metal plate. What are these metal plates called? This is what it looks like when it is removed: (The gold coloured ...
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0answers
51 views

Why does it take less force to mate a full-detent SMPM connector than to demate?

As seen in the table at the bottom of the page the mating force of a full-detent SMPM connector is less than its demating force. This is the opposite of every other type of SMP/SMPM connector listed ...
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13 views

ACTIVE_SCAN_RESULT_SIZE vs CONNECTION_SIZE in MiWi

I'm having a hard time trying to understand how MiWi works. I already read all the application notes and examples and now I want to setup a MiWi network (not P2P, not MiWi PRO). For example, I need a ...
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4answers
55 views

GPS Antenna Selector: How to electronically select one antenna from multiple available antennas?

I want to connect multiple GPS antennas to a single GPS module and select one of them based on some logic. Basically, I want the module to receive signals from only the selected antenna. Is there an ...
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7answers
1k views

Schematics for a simple radio transmitter that can be built only with passive components?

Fantasized in some of the survivalist, post-catastrophic novels, movies or docudramas is the radio built only with handcrafted or scraped components. Beyond the popular appeal of this stories, I ...
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1answer
25 views

Could transmit/receive turnaround be improved by having a heterodyne receiver switchable between high-side and low-side injection

In some of the small radios I've worked with such as the Nordic Semiconductor 24LE line, there is a significant (100us+) delay between transmitting data and being able to receive a response. By my ...
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3answers
74 views

How exactly to track oscillator in superhet receiver

The IF is 490 kHz. I have learnt that the local oscillator and the tuning block before the IF stage must "be aware of each other" or track. So in my case, the tuning of both the circuits should differ ...
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14 views

Common failure modes of full-detent SMP connectors?

Full detent SMP connectors are rated to a maximum of 100 mating cycles. What are the typical failure modes of an SMP connector that has experienced too many mating cycles?
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1answer
66 views

How to tune a radio receiver using a crystal oscillator?

I'm building my first radio receiver (a simple Ramsey HR-40 kit). The "Alignment" section of the instructions requires that I have some other device which I tune my receiver to. Since I have no such ...
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1answer
54 views

Radio Receiver IC

I am a Junior EE student that is interested in putting together a small radio receiver project for fun and to get some general practice with design. I have found these receiver chips from Silicon Labs ...
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2answers
73 views

RF Energy Harvesting Project

I am presently working on an energy harvesting system using RF signals. I have read some of the other posts made on this topic and have learnt quite a few things. However, I have some questions that I ...
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5answers
544 views

Very high speed counter (around 1.5 GHz to 2 GHz)

I am thinking of a device that can measure the distance of an object from a sensor using a radio transmitter and receiver pair. I'm thinking of using a counter at the sensor side, with a ...
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66 views

What kind of antenna is this?

The product page for this antenna supplies meager information. Do any of you RF gurus have a guess what kind of antenna this is as well as any other insight or reference radiation patterns?
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2answers
86 views

Headphone cable as antenna

How can headphone cables act as Antennas for built-in radios in smartphones ? Is it possible because of different frequency channels or what is the theory/mathematics behind this? On a side note, ...
3
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2answers
67 views

CC1120 and RF output pin and network

I am working on a hobby design and thinking of using the CC1120 for my RF transceiver. One thing that has me confused, however, is the matching circuitry on the RF input and output of the CC1120. ...
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1answer
57 views

Calculating the “ball-park” range of a transmitter including dBi

I'm looking to buy a tranceiver that has a LOS range over 100m at minimum 1kbps. (preferred 28kbps). I've been looking at this device I'm using this calculator and I'm getting over 180 miles which ...
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2answers
36 views

Multi-antenna extension for NFC

Like many, I am new to this. I am working on a project that would require a short read range over a covered space, like a person's body or table top. Could I make an extended antenna from my smart ...
2
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2answers
74 views

How does Altium Designer's “impedance constraint” feature work?

Altium has a design rules option for setting a track width constraint according to line's impedance (e.g.; 50\$\Omega\$). How do I use it? Please give me instructions or a link to an online tutorial. ...
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3answers
48 views

Using Bluetooth 4.0/LE verses RF

I am asking this question in hopes to get a solid answer from anyone who has direct experience dealing with the most recent RF as well as Bluetooth 4.0/LE developments. What I am essentially trying ...
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3answers
129 views

RF transmitter circuit explanation

I just can't get my head around how these RF transmitters work: simulate this circuit – Schematic created using CircuitLab What I do know about them is the following, correct me if I am ...
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3answers
125 views

loop area and EMI

I always hear something like "reduce the loop area" when reading materials on EMI reduction. Why we need to minimize the loop area? I have two guesses: Smaller loop area will influence less signal ...
3
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0answers
125 views

How to avoid regulatory approval regulations, when chosing a RF module?

I've been trying to implement RF capabilities into my projecto, but I don't want to pay thousands of euros to get an ETSI certification in case it gets into production. I know that if I get a complete ...
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1answer
20 views

Displacement current generation in dielectric and in vacuum? How is it different?

I understand how the displacement current work in dielectric such as in parallel plate capacitors but don't know how they would work in a vacuum where there is no dielectric present. Can someone ...
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1answer
61 views

Improving reception of 318MHZ remote control

We have a gate opener with keyfob-type RF remote transmitters that operate at 318MHZ. The range from inside the car is about 75 feet -- less than we'd like due to the time taken by the gate ...
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2answers
55 views

How to protect a RF chip from thunderstorm static electricity?

I'm working on a open-hardware wireless wind sensor. It's designed for being installed on mountains, where thunderstorm are quite often. I use a Si4461 RF chip, with a half wave whip antenna. My ...
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0answers
74 views

Getting the best range with XBee-Pro 900 XSC S3B

I have a pair of 900 XSC S3B xbee pros and a couple 2dBi duck antennas. I just did a simple outdoor range testing and only got about 2,000 feet. I was outdoors without any buildings in the way, but ...
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2answers
67 views

Perform digital modulations (HW or SW)

I am considering doing a project which revolves around microcontrollers (AVR, or arduino) and digital modulation to learn about digital RF. I have simple things in mind, just for experimentation. ...