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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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56 views

How cell sites work? [closed]

In Mobile communication, how do cell sites communicate to each other to the point when they reach the cell site which is connected to the other mobile phone when I make a call . What is the medium of ...
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0answers
44 views

Active phased antenna array for Wi-Fi efficiency compared to a directional antenna?

I'm interested in mesh networking of poorly controllable autonomous aerial vehicles (like blimps), so i wonder whether it is viable to use a phased antenna array versus a few traditional directional ...
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1answer
58 views

How can I calculate power consumption of the amplifier from its datasheet?

In datasheet of the transistor, CGHV40100, I could not find the power consumption of its. How can I calculate the power consumption? Datasheet of the CGHV40100
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58 views

Track impedance for CC1101 transceiver

I'm trying to make my own board for a CC1101 transceiver that will operate at 915 MHz. To do that, I'm just copying the reference design layout from the ...
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3answers
154 views

Methods for confirming on both sides that a signal was received in one direction

Say there are two devices (A & B) that talk to each other (full duplex). For the sake of this example, let's say the medium is RF (wireless). If device A sends a message to device B, what ...
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1answer
30 views

How to bias MOSFET for finding S-Parameter simulation?

I wanted to use a BSIM4 model of NMOS in my circuit. I got the correct dc biasing point, certain VDS,VGS and IC. But I am having issues measuring S-parameter data for MOSFET amplifiers. I simulated ...
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2answers
50 views

How to make BJT/MOSFET work in RF?

I am trying to design an amplifier with a transistor model. I followed some basic tutorials online (http://microwave.eecs.utk.edu/ECE545_files/02_Lab_2.pdf) and designed a transistor model for BJT/...
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1answer
38 views

Does the Si4731 / Si47xx provide the necessary info to fetch left/right demodulated audio levels?

I'm working on a project which uses an Si4731 broadcast radio receiver IC (Si47xx family) and which calls for left & right demodulated audio level meters based on a source FM broadcast signal. I ...
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1answer
60 views

Help identifying type of LC oscillator

I am trying to understand the RF transmitter (Q1) part of this schematic: (source: https://fccid.io/KUJCE9001/Schematics/Schematic-Diagram-171495.pdf) What type of oscillator is it? Colpitts, Harley,...
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2answers
74 views

How to detect RF / Wifi radio device nearby

I wonder if there is a way to detect if there is any RF/WiFi radio ON nearby? I'm configuring an ESP8266 12E module in STATION MODE (not Access Point) to connect to a Wifi network (any Wifi network). ...
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3answers
85 views

Is a modern radio wave broadcasting station a very fast spark gap transmitter?

In a spark gap transmitter, is that a "real" radio wave that is produced? I know you can hear it on an AM radio, if you are close to the gap, but is it a radio wave the same as from a radio station? ...
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1answer
82 views

Power amplifier simulation and real time experiment mismatch problem

Thanks in advance to anyone who will take the time to read my first post here. At present, I am doing a simulation of a power amplifier in LTSPice. The schematic and relevant files are uploaded in a ...
0
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1answer
110 views

Why does a classic envelope detector produce a negative voltage for some periods, when high frequencies are put in?

I'm playing around in ngspice & trying to understand envelope detectors for ham radio. I'm pumping 150Mhz into the circuit described below - I'm expecting it to go positive in proportion to ...
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2answers
51 views

Help Shielding RF Anechoic Chamber - FM Stations

a collegue and I acquired a surplus small anechoic chamber (8 ft x 8 ft) for making some pre compliance test measurements, and we're running into the issue of FM Stations being only attenuated around ...
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2answers
59 views

Do I need to consider RF power splitters for signal <1kHz?

I need to tap a signal on a BNC cord to record it with a Labjack ADC. The signal is very low frequency, as the FFT shows. I was planning on using an RF power splitter to add a line to the Labjack. ...
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2answers
85 views

Converting from OOK to ASK at 433MHz

I need to convert messages sent from a device using OOK modulation to ASK so it can communicate with another device that modulates in ASK. I can't modify either of those devices. I was wondering if ...
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0answers
23 views

Finding output SNR using Noise figure

am trying to solve this question below: So I did find the system's overall noise figure to be 2.3 = 3.68dB, and you are more than welcome to verify it. However, my problem now is to find the output ...
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2answers
97 views

Using audio instrument cable for 1MHz transmission

I'd like to transmit digital data together with an audio signal along an instrument cable. In more detail, I'd like to send MIDI data and the audio signal of a guitar on a single cable. The rationale ...
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1answer
39 views

Why real part of load change as we look through transmission line?

As we move from an imaginary load towards generator through a transmission line, we can see that real and imaginary part of that impedance changes. In fact, an ideal transmission line is comprised of ...
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1answer
110 views

Mounting orientation recommendations for PCB spring antenna?

I have been looking at 868MHz through-hole spring antennas for an application, but I can't seem to find any sort of information in datasheets regarding layout recommendations. Here's the most ...
0
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1answer
66 views

How can I measure my smartphone transmitted power? [closed]

I was wondering if I can measure my phone's transmitted power with an SDR by tunning in the transmission bandwidth but then, I'm not sure how to know whether this power is coming out of my phone or it'...
0
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1answer
123 views

Impedence Matching of Antenna and Coaxial Cable

There is a scenario based question which is confusing for me Antenna had four rods each 15cm arranged as a plus sign. its brass shielding was cut and it had two 75 ohm coaxial cables in it. one 10 cm ...
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1answer
49 views

Correlation EMF / DNA

What is the current state of independent (of producers) studies about the correlation between EMF (with particular reference to mobile devices) and interruption of human DNA? Are the declared SAR by ...
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1answer
40 views

How does Return/Insertion loss work for wireless devices if there’s no cable?

I understand return loss is the ratio of how much signal is reflected in a transmission line. But for wireless devices there is no cable. So how is this measured? So is the impedance mismatch for ...
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2answers
97 views

RF range at 169 Mhz

I'm planning a sensor network for agriculture (that apparently doesn't exist yet in this form) and I'd like to understand the possibilities of the radio link. A good number of in-the-field soil ...
3
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1answer
437 views

Why is this BJT Schmitt trigger producing a sine wave?

I am trying to build a Schmitt trigger from a pair of BJTs to convert a sine to a square wave. The sine wave is from a Colpitts oscillator running at over 150 MHz. I want to measure the ...
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1answer
53 views

How to connect terminals like Ground Lugs and Feed-throughs?

Feed-throughs, ground lugs, and similar terminals are often found on RF test equipment. What is the standard way to connect these to wires-- wrap stranded wire and solder? Is there a part that assists ...
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1answer
56 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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0answers
50 views

Derive required carrier to noise or signal to noise from receiver sensitivity on FM receiver

Can I extrapolate the required C/N based on reported receiver sensitivity? I'm plotting coverage for a repeated radio system for handheld radios. The system is analog, FM narrow band. I've ...
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1answer
43 views

LC Network in Microchip's LoRa Gateway

I am reading the microchip's LoRaWan Gateway manual. On Page 48, I got stuck at receiving side on the LoRaWan RF circuit. It ...
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2answers
115 views

Design a tank circuit for class C power amplifier using ADS

I am trying to figure out the best values for the tank circuit values (L and C) in order to compare the amplifier's efficiency with the output power I have chosen the tank value L1 and C7 to resonate ...
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0answers
37 views

LC oscillator emitter current doesnt go to 0(class C)

Im trying to create a 433MHz oscillator with the help of ADS for the simulation. From the lectures i have had on transistor LC oscillators, i know the are forced into class C operation, and that ...
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0answers
51 views

Why does the solution to the wave equation define two directions?

I've been studying transmission lines recently and I'm struggling to reconcile my intuition with the derivations. Take the form of the general solution to the wave equation given on this page antenna ...
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1answer
61 views

Understanding the Practical Application of a Simple Antenna made from Coax

I am here today to gain a deeper understanding of the fundamentals of using antennas in RC applications. I am trying to understand what exactly is going on with a particular 2.4GHz receiver a picture ...
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3answers
77 views

Ambiguous symbol [duplicate]

Does anybody know what this symbol presents?
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4answers
143 views

How to amplify RF signal to high enough level for a CMOS downconverting mixer?

I've been reading original academic papers on mixers and now a RF textbook and I have been unable to understand a very basic thing, which is how do I get a RF signal, say -65 dBm, at a high enough ...
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0answers
14 views

TH7122 Transceiver debug procedure

I'm trying to use a Melexis TH7122 Transceiver IC in the 915 MHz ISM band. The problem is that I don't know how to make it work. More importantly, I don't know how to see if it is working properly. ...
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0answers
47 views

SNR wall definition

I want to ask you if my understanding of the definition of the so called "SNR wall" is correct and complete. The SNR wall phenomenon is described here and here. If one has further information that ...
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1answer
36 views

RF switch(1:14 or 1:16) without signal distortion [closed]

I am looking for an RF switch with no signal distortion in the 1 to 2 GHz band. I need a 1:14 or 1:16 switch, could you recommend switches(for example, an optical switch or a semiconductor switch etc)?...
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1answer
107 views

How do LoRa end-devices configure their upstream and downstream communication?

I'm in the process of building a LoRa end device, and am also designing protocol. I plan on using the channels specified in the AUS915 ISM Band as outlined in the LoRaWAN regional parameters (though i'...
0
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1answer
72 views

dBmi Meaning in Testing

I'm having trouble making sense out of this requirement, in terms of how to test for it. I have a specification stating that for an RF power level measured in dBmi (let's call that power level S ...
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1answer
83 views

EHF RF Transmitter and Receiver

We are working on a blood glucose meter that will measure BG readings through radio waves with a frequency between 60-70 GHz. That range is necessary to allow penetration through the tissue and we ...
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0answers
57 views

Beam Steering range of a phased array antenna system

What is the beam steering range of a phased array dependent on? For example, if I use an antenna array of Nx1, with a phase shifter resolution of \$\frac{2\pi}{k}\$ and the antenna elements spaced at \...
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1answer
36 views

True near field distance for a short monopole antenna

Antenna properties: Height x Diameter = 3.3 inches x 1.4 inches Test Frequency: 900 MHz (Wavelength = 33 cm or 13 inches) I see some conflicting formulas to calculate the near field distance for ...
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0answers
21 views

HM-TRP radio module works at 56K data speed but only in delayed chunks

I created the following setup: I created one circuit in which the PC connects to an HM-TRP radio module via a max232 DIP IC. This circuit for the test is the master to all devices and sends a 16 byte ...
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3answers
255 views

LTSpice is frustrating me. Why isn't this Class C amplifier working? I can't get a sinusoudal output

I've been trying to research how a class C amplifier works, and it makes perfect sense to me, but I'm having problems getting it to function in LTSpice. I have the latest LTSpice version (XVII with ...
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1answer
151 views

Pi-Matching network needed when already 50Ohm matched on transceiver?

I've been dreaming up a small gadget featuring a NRF51822 MCU as a centerpiece and I'm a total noob at RF-voodoo. I want to use a chip antenna. My question is this: Do i need this matching network ...
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1answer
102 views

RF Combiner Losses

I'm having a hard time understanding what is actually achievable with an RF combiner. Let's consider this scenario, here port 1 of the RF combiner has a sinusoid at f1=100Hz and port 2 has a sinusoid ...
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1answer
136 views

Gerber Viewer With Good Measurement / Distance Tools?

I'm trying to measure some trace widths using Camtastic in Altium. I have to say, I really find Camtastic very finnicky when I try to zoom and pan. The measure distance function (which I am trying ...
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1answer
54 views

Choosing reactance of LC tank for crystal oscillator

In the ARRL (2011) Section 9.5.4 (talking about a series mode quartz crystal oscillator) it says: To build a practical oscillator from this circuit, choose an inductor with a reactance of about ...