# Tagged Questions

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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### At what cable length does matching the impedance at the ends of the cable become important?

I'm building a base for a PMT that outputs pulses of width <=1 µs. In Hamamatsu's PMT handbook it states on pg. 112 (emphasis mine): When using a photomultiplier tube which is not a fast ...
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### Do consumer high temperature RF ASICS exist at 200C?

So at lunch I was browsing Indiegogo projects and I saw this one here It's a wireless meat thermometer, I've seen it in some permutation or another a few times on sites like this. Apparently no one ...
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### How to calculate the line impedance for WLAN antenna path and how to determine which kind of antenna is efficient for automotive product

I would like to know how to calculate RF antenna Line impedance, and makes the Pi filter values exactly in my Antenna path. I need a general guidelines and clear understanding of it. Please help me ...
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### Are there transceivers that can be used for a mesh topology at ~1km range with >1Mbps? [on hold]

I've been struggling to find some transceivers I can use in a project I'm working on. I'm interested in creating a mesh topology with each node separated by about 1km. I'm curious as to how it can be ...
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### Can all RX and TX chips be made compatible with each other? [on hold]

I have quite a few Radio Controlled Toys, Some I have hacked so that they become autonomous. This gave rise to a question: Can all Receiver (RX) and Transmitter (TX) chip be somehow made compatible ...
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### Inductance values over the frequency

Does inductance vary over frequency in passive components. Consider a Coax cable for example, does the inductance value change as a function of frequency, lets say from 5GHz to 100GHz, does the ...
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### RF Scheme for fast DAQ (accelerometers)

I am looking to design a data aquisition scheme for a field project where initially 5-10 3-axis accelerometers will be placed on a flexible object to gain information on the amplitude reference forces ...
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### Baseband Processor

If a device can only be activated by way of RF then I would tend to believe that the BB processor (embedded via ASIC design) would need to be active and powered on yes ? If correct then does it have ...
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### Dipole antenna RF Layout

I am designing RF layout on PCB, my PCB is in Circular form, In Pic 1, is my current layout in PCB, since this chip antenna is dipole in nature , so to form the dipole antenna there should be mirror ...
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### WiFi obscuring 433mhz signal reception

I have a WiFi arduino device with a 5dbi omnidirectional antenna and a 433 mhz receiver board, based on Aurel AC-RX with a 17cm stranded copper wire Antenna both enclosed into the same box. This ...
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### Is it possible to induce RF Emissions from a RF enabled Device

Would it be possible to take a device anything such as a wireless router or a wireless video and induce unintentional RF emissions while no power is supplied to the device ? Can you send it some range ...
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### Linear Rise exponential fall pulse generator

For a neutrino detector related experiment, I need to design a circuit which generates the pulse similar to the detector. This is required to test the front end electronics. Here are my final goals: ...
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### How does a device that is RF enabled power up the main CPU by way of RF?

Suppose you have a device such as a wireless video camera and the only way to power on the device is by way of RF. If the video camera has a CPU how can the baseband IC power up this CPU ? Is it ...
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### How to determine the limit to the number of bluetooth masters in a given area?

I am working on concept development for a sensor network and considering scale-up issues. I have found plenty of info on the number of devices a bluetooth master can connect to and I have found a few ...
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### How to power on a power on (activate) a backdoor core via RF? [closed]

Ok lets suppose there is a backdoor system embedded on a processor or CPU IC. This system (core, embedded os) can be activated only by RF. I don't know the frequency (range) which it uses. So my ...
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### preventing Cell Phone from interfering with car cassette adapter [closed]

My old car has a cassette player and I use an adapter for my MP3 player. I was hearing strange interference occasionally and finally figured out that my cell phone causes that when a call or message ...
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### External whip 868MHz Antenna via coaxial cable. Ground Issues

I have a RF module that works at 868MHz.It works as transmitter and as receiver. (lambda:0.345m lambda/4=8.64cm). The RF module ground plane (GND_PCB) is 10x10cm, so bigger than lambda/4. By default, ...
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### What is the transmitted power (dBm) of a mobile phone when 4G connection is enabled? [closed]

Is it unhealthy to leave the 4G connection on all the time? When talking on the phone, should one turn off 4G because the phone is just next to the head?
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### How do I design an antenna in desired frequency with preset equivalent circuit model?

I am working on a project that an oscillator drives 1 mH inductor in 7.5 KHz. This oscillator also happens to be very efficient. However, I am constrained with inductor value. So, to make my design ...
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### How did four-course LF radio navigation ranges have their beams other than at 90° / 180° angles?

The four-course Low Frequency Radio Range system used for aircraft navigation (in the US and elsewhere) in the 1930s and 1940s used a pair of directional antenna (with figure-of-8 shaped radiation ...
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### What do I need in order to make my arduino to transmit / recieve signals exactly at 433.68 MHZ?

Before I start, please note I am not even near to be an expert in electronics - I just try to do my best with what I have - I apologize in advance if my language is not technical enough. I have a ...
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### Is it possible to distinguish unintentional RF emissions from two different devices?

Let's say that you have a CPU on a PC motherboard and a RF transceiver device in the design of the CPU which is not operating or activated. Is it possible to distinguish the unintentional RF emissions ...
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### How does an RF transistor bias work?

In many RF applications I have seen transistor circuit that looks something like this: simulate this circuit – Schematic created using CircuitLab Now, I understand the role of all the ...
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### What is the output impedance of HF power amplifiers?

In case it matters, let's discuss solid-state, linear, class AB amplifiers operating below 50 MHz and on the order of 100 W. Here's my confusion: I'd think ideally, the output impedance of the ...
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### Minimum threshold fm equation

I have been searching and working to understanding this equation below in relation to FM signals minimum threshold. Pr [dBm]= (Eb/N0)+10∗log10(Rb)+N0 −Gm Eb is the energy per bit to noise power ...
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### Interface of HC05 Bluetooth module and RF 433Mhz Module

I am trying to make an Android controlled toy car. Now the range of the bluetooth module is around 10 meters. However, to increase the range, I decided to interface the RF module with the Bluetooth ...
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### Good faraday cage to block bluetooth beacons

For a project I need to test often with bluetooth beacons linked to an iOS app. When I'm at home (office at home) I like to reduce exposure to radiation as much as I can. Not in a obsessive way, but ...
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### How to find the resonant frequency of a human body?

I've read that the human body has resonant frequencies somewhere around 50MHz. I also think it would be interesting to look for values in other ranges like 10-100 kHz. I'm wondering how to build a ...
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### Boost a HV power supply from +1250 V to +1500 V

I'm designing a base for a photomultiplier tube using a recycled HV power supply. The power supply is an EMCO C12. The base has a 14 pin socket (to connect to the PMT), the EMCO C12, a DAC to program ...
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### Initial permeability of toroids in ATX power supply?

I'm interested in re-using output side or possibly the line filter toroids from a junk ATX switching supply. All turns are removed, just the core. I think these are powdered iron cores and any guess ...
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### Significance of Linearity in RF Power Amplifiers

I have started studying the topic of "RF" Power Amplifier (PA) operation, and so far I have come across description like, if PAs are non-linear, it does not form a straight line and rather it has a ...
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### BJT Capacitance at RF limmitations

I am trying to design a simple RF signal buffer using a MPSH10 BJT transistor. This is to operate at ~90MHZ and simply buffer an input RF signal to lower the out impedance of my oscillator which feeds ...
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### Drawback of RF BJTs

So when manufacturers build transistors they always have to trade-off certain parameters for others. RF transistors often have a high gain-bandwith product and low capacitance to make the gbw usable. ...
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### Better data encoding for 433 Mhz OOK communication

I'm looking for a Manchester Encoding alternative for 433 Mhz OOK communication. Is 5B/6B data encoding appropriate for this application? It also provides 0 DC voltage average. And it doesn't require ...
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### How to fix a frequency shifted audio part of an RF signal?

I tried to connect an old Japanese (NTSC, System M) video gaming system (an original Famicom, HVC-001) to a rather modern multisystem LCD TV-set (Sharp LC-43CFE5222E). The TV tuner is capable of ...
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### RF one-shot circuit capable of producing 5-ns pulse [closed]

I am looking for a one-shot circuit capable of producing a 5-ns output pulse with short switching time. I saw this one (http://www.nxp.com/documents/data_sheet/74LV123.pdf) in a previous question, ...
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### How can I check a transmitter module for antenna continuity of its connections?

I am soldering a IPX U.fl PCB Mount Socket connector to a FlySky 2.4 GHz module and I want to check that I have proper continuity connection with my soldering. See here where I have more info: ...
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### how to reproduce a matching network of a vendor

I'm trying to create a board using the BGT24MTR chip from infinion. I noticed that they said that there is a Tx/Txx impedance. To compensate for this impedance they created a matching network. ...
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### ECL output termination

This is a rookie question, but I'm quite confused about the ECL termination used on the ADCMP565 evaluation board First, in the IC datasheet, they show how to terminate the ECL outputs to drive 50Ω ...
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### Adjusting OCXO frequency via VFC pin

I have a used OCXO Morion MV85. According to datasheet linked above, it has GND, VCC or Uin, RF out and VFC pins. As far as I was able to find out by googling, the purpose of VFC pin is to adjust ...
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### What is the coupling coeffecient of a 10.7Mhz if transformer?

Does anyone have a rough range? I just need to be in the ball park. As an experiment, I'm simulating some if amp circuits in LTspice and it looks like they are very overcoupled when using a coupling ...
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### Is it possible to transmitting video signal on 433MHz? [closed]

A video of 2MP or lesser at a distance of 2-3Km. Is it possible to transmit it on 433MHz ISM band?
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### RF power meter circuit

I want to setup a radio transmitter and reciever a few centimeters apart and measure the signal strength i get. There will be a filter in between which absorbs particles and the idea is that i want ...
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### Raspberry Pi 2 to arduino RF Serial link with USB to Serial TTL Converter

This is my first question here. I want to have a communication channel which will use a 433 MHz RF TX-RX pair. I want to use a Raspberry Pi 2 as a transmitter and an Arduino Mega as a receiver. Is it ...
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### How to identify a component on a board?

I am trying to identify a component on a board of my roller shutter remote control. Here is the board: The main component is very likely the one top-right, identified by ...
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### Making aluminium conductive for an RF shield enclosure

I'm not sure if it's appropriate to ask here, but I would assume many people in electronics would have experience with this. I'm enclosing an RF sensitive PCB into an sealed aluminium enclosure. ...
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### Options for matching 75 to 50Ohms on PCB

I'm collecting information for a project I've got in mind. Clarification: I'm not looking for someone to help me do the calculations. I'm not to that point yet. I'm basically looking for "the ...
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### How to Filter Very High Voltage Power Supply Noise

Any suggestions of how to filter out this noise? Basic filter math is not working out. I am adapting a cheap commercial HV supply (variable DC voltage up to 40kV at 10mA) for physics experiments. ...