Questions tagged [rf]

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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8k views

newbee wants to know about 315 / 433MHZ

i want to send some signals on the 433 MHZ band. Now i've bought a device (CDT-88) and it says 315/433 MHZ (RF Wireless Transmitter Module 315 of 433,92 MHz CDT88) after some searching i see a lot ...
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125 views

Understand RFID credit card protection case

My parents bought credit card case which protects against RFID sniffing (aluminium foil but only on one side of the case), i was skeptical because i thought it would work only on one side. So i got ...
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28 views

SIM800L Auto Connect..!

I want to know does the SIM800L module connect to the network automatically without any user commands? Because some modules will disconnect in low signal areas & some SIMs will be disconnected by ...
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27 views

Broken RF remote [closed]

The broken RF remote did operate a TV lift. The lift has no identifying name, manufacturer so I can't contact them for a replacement. The remote is 2.4. Is there a way, perhaps a device that would ...
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33 views

Fm receiver circuit doubt

I was trying to simulate an FM receiver circuit on LTSpice. The circuit is given on this website I want to know how the correct current/voltage will look around the speaker (modelled as 8-ohm ...
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3answers
132 views

Schematics RF transmitter

I'm attaching a schematic of an RF transmitter made by Synoxo. Chip is the SYN115. The schematic is found in the datasheet. I do not understand why L3 which is the PCB antenna (pointed with the red ...
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1answer
20 views

NFC Loop Antenna placement

I'm trying to design a NFC loop antenna according to the following specification: http://www.ti.com/lit/an/sloa135a/sloa135a.pdf In the design the loops are placed on the top layer of the PCB, same ...
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1answer
195 views

Alternative wireless technology for passive RFID tags

I am working on a project where I have 3 boxes and a RFID reader (mfrc522) attached at the bottom of each box. I keep my wallet/keys/etc in these boxes and a LCD screen displays what is in each box ...
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1answer
109 views

Compatibility between XBEE-PRO 900 HP and XBEE SX

I wanted to use a 900 MHz xbee and I need one side to be surface mount. So I'm thinking of getting an XBEE PRO 900 HP (XBP9B-DMST-002) and an XBEE SX (XB9X-DMUS-001). These devices have the same ...
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1answer
30 views

Is it possible to combine two CFU455IT +/-2kHz (4kHz) ceramic filters to get a +/-1.25kHz bandwith (2.5kHz) filter?

Can I put two of these cheap (less than 3USD) and common CFU455IT +/-2kHz (4kHz bandwith -6dB ) ceramic filters in series to get a lower bandwidth good for SSB TX? If I'm correct I will get -12dB at +/...
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190 views

BLE and Bluetooth Classic Coexistence?

we are designing a fairly compact PCB for a communications device. We are looking at using BLE as a link for voice to a separate microphone, and BT Classic to be paired with a smartphone. We are using ...
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RF Impedance Matching Network Phase differences/shifts

If there is a coax transmission line with the EM field propagating in the TEM mode and I measure the voltage signal off the inner conductor to an independent ground not part of the RF circuit and ...
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102 views

HFSS port 'Port1' does not have a valid reference plane above or below it

How to get rid of the following errors: planar_marchand_balun (C:/Users/kevin/Documents/Ansoft/) EMDesign1 [error] An error occurred during the mesh generation. Check the message window ...
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1answer
1k views

How to make an rf choke and tx rx coils?

I am a tinkerer and trying to make a wireless charger in which I felt difficulty in making an RF choke coil of 8.6uH , 0.674uH & 1.235uH Can anyone please help me out?
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Using a single MOSFET as an RF switch

I'm assembling a receiver kit from QRP labs. It is an inexpensive kit designed to cover HF. This kit has a BS170 at the input which I assume is intended to disconnect the receiver when the transmitter ...
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2answers
63 views

Non-90deg mitered bends

Is there an approximate equation giving the optimal miter for a non-90degree mitered bend? In particular, I'm trying to determine the correct miter for a 45degree bend. There are a number of resources ...
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1answer
123 views

Sequencing modes for FCC “Intentional Radiator” test

I'm FCC certifying as an "intentional radiator" a product that uses a custom antenna and off the shelf Broadcom WiFi module. The module has an antenna port, so single-modular and limited single-...
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5answers
3k views

Faraday cage with a RF WIFI router inside - does the electricity “evaporate”?

I have a Faraday cage and inside there is a WIFI router whose RF I am trying to contain. The cage is made of aluminium mesh with hole sizes of 3 mm or so. What happens to the RF electricity coming ...
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2answers
72 views

What is the purpose of this capacitor in the SA602A circuit and how do I choose its value?

I'm trying to use the SA602A mixer and I'm not sure what the capacitor between the emitter and the base does. I'm using this mixer because I've seen it being used in the Norcal40. However in the ...
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20 views

Find PCB Antenna impedance and matching circuit

I'm working on a project that uses NFC interface. I need to design two antennas: one for the RFID tag and another for the NFC initiator. I decided to use the design proposed in the evaluation kits. ...
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58 views

Detecting an electrical connection without a complete circuit

Wired Fencing In a regular (wired) fencing system (for sabre and foil,) contact is determined simply by applying a current to the weapon through a wire and forming a circuit between a conductive ...
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33 views

RFID reader array using row/column RF switches (multiplexers)

I need an 8x8 grid of RFID readers arranged on an 8"x8" board. The RFID tags will be placed only millimeters above each antenna. I was wondering if I could use one 1:8 RF switch (e.g. pSemi PE426482) ...
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1answer
95 views

DRM'd hand sanitizer dispenser

We have a newborn and rely on hand sanitizer when changing diapers, and we ran out at an inopportune moment in history. By some stroke of luck, I managed to snag one of those "industrial" touchless ...
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1answer
101 views

500 mW RF amplifier for 170 MHz design

For a new project I need to build an RF amplifier for continuous-wave with about 500 mW (27dBm) output at 170 MHz. It doesn't need to transport data, it is only for measuring purpose. The input ...
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32 views

Calibrate for an inaccurate 50 ohm load in a DIY Vector Network Analyser (VNA) based on a VSWR RF bridge

I have built a "DIY VNA" using a frequency generator, an SDR receiver, a RF Reflection Bridge and a 50 ohm load. This is used to measure "VSWR values" of antennas to see what frequencies they are ...
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66 views

RF Power Amplifier outputting insufficient power

I'm using an SE5004L 5GHz power amplifier to generate a transmission signal in a radar application. I've designed the output power of this amplifier to be about 26dBm. Unfortunately, the measured ...
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1answer
381 views

Optimizing short antenna for 27 MHz

(It's really a continuation of a previous question but it is old so I decided to ask a new one with more detail) I have a colpitts oscillator designed for 27 MHz going into a short monopole antenna ...
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66 views

Key fob receiver reverse engineering: IC identification

I'm doing reverse engineering on a hardware of an equipment, this equipment is able to identify the presence of a RF signal from a key fob. Unfortunately, it was not possible to identify the ...
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4answers
2k views

What does SMA Tee Adapter do?

SMA tee connector is something like this: What does it do? Is it something like a power divider?
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2k views

What are effects of attaching more antennas to Wi-Fi router via RP-SMA splitter

Theoretically and practically speaking what are effects if in typical Wi-Fi router attach more than one antenna per output using something like RP-SMA Splitter and or extension cable ? In my case, ...
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30 views

Receiver input return loss , Noise Figure and SNR

Suppose I measure a receiver NF and also its input return loss. The known approach to calculate input referred SNR ,say at sensitivity level is: signal power at sensitivity level/ noise power over ...
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Signal to Noise Ratio and return loss

If I measure a receiver NF as well as its input return loss. Then SNR = signal power/ noise power over the whole signal BW. Note that NF is used here Now a bad return loss implies that part of the ...
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1answer
240 views

Matching impedance network for an LC ladder network

Let's say I have a 5 stage L-C ladder network with L= 4.7 micro Henry and C= 60 pF. The characteristic impedance of the network becomes 280 ohms (square root(L/C)). However, from circuit analysis, the ...
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107 views

Receiver Antenna Gain

How is gain defined for a receiver antenna? If we look at a radiating antenna, there is a Pin, and the gain in a particular direction would be the radiation intensity Ur, divided by the radiation ...
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1answer
45 views

Soldered wire or test connector for VNA measurement?

I am designing a PCB for a IoT device, which will have an antenna inside a space-constrained plastic enclosure with metal screws. I know that I will have to tune the frequency response of the antenna ...
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2answers
37 views

Waveguide excitation through coaxial antenna

let's consider a waveguide excited with a coaxial cable antenna: You may see that this structure is sized with a distance between the antenna and the plate equal to \$\lambda/4\$. My professor has ...
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2answers
43 views

LF RFID signal jammers

I am currently researching into the security of RFID based access control in relation with jammers. For an experiment, I am trying to build a device that can jam 125 kHz RFID cards from like a meter ...
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2answers
123 views

Which remote communcation type should I use?

In my project I have to give only 4-digit number to each device(50+ devices) without any wire. And there will be only one transmitter for all receivers. Which communcation type should I use? ...
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2k views

building simple radio

I'd like to build a simple AM radio (so simple it will only receive a single AM channel). What is the simplest way to build a single channel AM radio that will output to an 8ohm speaker? (e.g. 1030 ...
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51 views

Electric field internsity of RFID loop antenna

We are going to export a fairly simple RFID product (Mifare, HF 13.56 MHz) to Japan and I am trying to figure out if we have to go through the full certification process or if we can register it as '...
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2answers
2k views

Expanding range of RF sender (FS1000)

I send signals using the FS1000A, i.e. 433MHz. The module has a pin named "ANT", where I can solder an antenna, like a short piece of wire. As the sender's range is not that far, I want to increase ...
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1answer
58 views

What does a discrete component mixer look like?

I'd like to make a poor man's mixer from scratch. Something that can down convert 7MHz to 100KHz. What would the circuit look like using only BJT/FETS or diodes? EDIT:I found some some using diodes. ...
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29 views

RF Communication Fresnel Zone Issues

I'm working on an two systems, each with the following connections: 433 Mhz 900 Mhz 5.8 Ghz All links are omni-directional and vertically polarized. Only 1 set of (3) links are active at a given ...
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2answers
37 views

One port Vector Network Analyzer (VNA) Calibration without the given standard Calibration Kit

I am trying to do a one port VNA calibration for measuring filters at the GHz band. The VNA that I am using is Keysight E5063A. However, I am running into some conceptual as well as some practical ...
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1answer
38 views

Bluetooth power standard values

Let´s say I have a device with a bluetooth (BLE) 5.1 radio and I would like to know when, using a mobile phone, the power received from the device is good enough to stablish a reliable communication ...
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1answer
357 views

How to find new ABCD parameters when reversing 2-port network

I have an ABCD matrix represenataion which is defined as: For such a problem, what approach should I follow in order to organize the new ( reversed) network ports voltages and currents properly. I ...
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1answer
109 views

High-voltage (HV) messing with my transimpedance amplifier circuit

I have a transimpedance amplifier circuit that takes 100kHz small current and gives the voltage output proportional to current amplitude. Everything works properly when nearby HV circuit is off. When ...
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2answers
38 views

Usage of non-linear phase filters in RF receivers

I'm in the process of designing the analog front end for a RF receiver. The system will use BPSK modulation. I was wondering what effect non-linear phase filters (such as Chebyshev and Butterworth) ...
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2answers
60 views

LC Filter / Matching - Why does this cap help?

this is my first question on the site, so please let me know if there's something I can do to write it more helpfully. The Problem: I'm building a small radio. At the output of my mixer, I need to ...
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1answer
24 views

Attenuation and Insertion Loss for a 2 port network

in my university lectures the insertion loss and the attenuation of a 2 port network have been defined in the following way (and I have an extremely basic question about them): the Lnsertion Loss L ...

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