Questions tagged [radio]

Consider also the rf tag.

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2answers
899 views

How many watts does a 40 MHz radio frequency signal create?

I am new to the study of electromagnetic frequencies and electrical engineering as a whole. I am trying to understand how to convert a radio frequency into energy, or calculate the power density of ...
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2answers
52 views

Relationship between radio transmitter output power and its input electrical power?

Given a radio station of a given licensed effective radiated power, is it the case that the transmitter requires at least that much mains power to run it? E.g., if a radio station says it's 100,000 ...
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3answers
150 views

Will this 'radio receiver' work?

I am a complete beginner with radio and electronics in general. I did some research on antenna designs and found that, with dipole antennas, at least from my understanding, the second antenna will ...
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2answers
95 views

Identifying strange amplifier types of amplifiers in a 1979 CB radio

I'm trying to fix an old Midland 3001 CB radio and I came across a few strange types of amplifiers in the receive stage of the radio. I was wondering if anyone could identify the type of amplifier ...
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0answers
52 views

Photons of RF energy [migrated]

So I start with the understanding that light is photons of electromagnetic energy, and that as the color gets more red the wavelength increases, and that an optical photon has both an electric and a ...
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1answer
104 views

Night-time Shortwave radio broadcast

I recently read an article from https://www.fcc.gov/media/radio/am-stations-at-night It says: During daytime hours when ionospheric reflection does not occur to any great degree, AM signals travel ...
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4answers
85 views

Substitute for 455 kHz Ceramic filters in new designs

I was wondering what has ever happened with the 455 kHz ceramic filters commonly used in the second IF stage of a superhet radio receivers? All but just a very few (and those left over don't seem to ...
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1answer
82 views

How do metal pipes amplify radio time signal?

I ran into this YouTube video on how you can amplify the signal for your radio controlled watches: https://youtu.be/wI4FwQMCN9w In short, the guy in the video said he stumbled on a way to amplify the ...
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2answers
69 views

Simple FM Radio Receiver project

I've been making my own simple FM radio. I know it's not quite appropriate to make this stuff on breadboard, but if it works, I'll move in on the board and solder it. I wanted to ask why my radio is ...
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0answers
47 views

Unable to intercept the code of my remote control at 433 MHz with RaspberryPi

I'm trying to reproduce the code generated by my universal 4-channel radio control with ...
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0answers
52 views

Radio static caused by windscreen wipers

I was driving past a radio station transmitter of the radio station I was listening to. I turned on my windscreen wipers, which caused a noticeable static to be emitted through the speakers for the ...
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1answer
72 views

How to avoid a MCU to run constantly when a superheterodyne radio receiver is receiving nothing, and possibly enter in deep sleep?

TL;DR: How to avoid an ATtiny to run constantly when the radio receiver is receiving nothing, and possibly enter in deep sleep mode? Configuration: ATtiny45 (on breadboard) SRX882 Superheterodyne ...
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5answers
83 views

Why is Frequency Conversion Additive in Acoustics Beating, but Multiplicative in Heterodyning?

In radio electronics, one of the first concept to learn is frequency conversion by using a mixer. And it's strongly emphasized that the mixer is a multiplier, not an adder used in audio circuitry. The ...
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1answer
59 views

Resonant Radar — How aspect independent is it? [closed]

Resonant Radar: transmitting at a bandwidth that encapsulates nearly the natural resonance frequency of a reflective object in hopes of illuminating it upon return (higher amplitude.) I have read ...
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1answer
76 views

Superheterodyne receiver channel selectivity

I am new to RF so I have quite simple question about topology of superheterodyne. I am facing with adjacent channel selectivity problem. The problem is that I can't obtain selectivity more than 40 ...
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1answer
28 views

Orientation of Loop Antenna (receiving mode)

I have done some measurements through a loop antenna similar to that shown in the following picture (all the informations included do not refer to my antenna, it is a picture used only to show its ...
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1answer
62 views

How does this 433Mhz garage remote control work without an antenna?

I have a 433 Mhz garage remote control that works very well even from 30 to 50 meters and it has no antenna! How is it possible that it works so well without an antenna? Also, given the picture of ...
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1answer
38 views

Crystal filter impedance matchin

I have a quite basic question about crystal filter impedance termination. F.e. ECS-45K20A 45Mhz IF filter - it has specified terminating impedance 910 Ohm / 2.5p. https://pl.mouser.com/datasheet/2/...
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1answer
36 views

PCB with 5 Pluggable RF modules and 1 LTE puggable module - will it cause issues for reception at different antennas?

I am designing a prototype PCB which shall have 5 pluggable RF modules and one 4G LTE module as shown in the image The Base board size shall be 240 x 140 mm, RF board size is 40 x 50 mm and LTE board ...
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0answers
55 views

Building a personal RF anechoic chamber in a large walk-in closet?

What would one need (besides many foam absorbers) to build an in-home small anechoic chamber for transmissions in the UHF to L-bands (specifically 500Mhz - 2 Ghz), and what resources would you point ...
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3answers
129 views

Design of an Automatic Gain Control Using a JFET

simulate this circuit – Schematic created using CircuitLab I have implemented the above circuit which is supposed to amplify a negative 200kHz sinusoid to constant amplitude even if the ...
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3answers
56 views

Does a “frequency-modulated” signal mean that the frequency isn't consistent?

Does a "frequency-modulated" signal mean that the frequency isn't consistent? and therefore it has a specific bandwidth of frequencies is can cover??
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1answer
20 views

Current waveform for LTE transmit

I am designing an IoT system which uses the SIM7000A. In the SIM7000 series datasheet it says that the highest possible current for LTE is under 200mA (section 5.4 of SIM7000 Hardware Design_V1.03). ...
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1answer
58 views

Shannon - Hartley Theorem

Let's consider the Shannon - Hartley formula for the channel capacity \$C\$: $$C = B \log_2 (1 + S/N)$$ I have two doubts about it: 1) is it correct for TDMA, FDMA, or CDMA? And why? 2) Can a ...
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1answer
93 views

Drift auto-corrector for any microcontroller [closed]

I've made multiple microcontroller circuits in the past, but now when I look at everything, drift has become a problem. I know this when I try to connect two micros together serially via wireless ...
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2answers
108 views

Fixing an old radio [closed]

I am trying to fix an old radio that my girlfriend just bought. It's from around 1964. I'm just a normal electrician and I am not used to fixing things like this. Radio model: Huldra 7-45 Skapmodell ...
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0answers
33 views

radio Link works with laptop but not with PC

I have a complicated issue. I set my HM-TRP radio modules to use: 117Khz receive bandwidth, 39Khz deviation frequency and 38Kbps air and data rate. The attached picture is my basic room setup for ...
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1answer
50 views

RF External matching network - mixer IC

I have question about mixer IC (Max2335), datasheet: https://datasheets.maximintegrated.com/en/ds/MAX2335.pdf LNAOUT and MIXIN in pin description (p. 5) have notice: "Requires an external matching ...
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1answer
36 views

How high should I make an FSK modulation index value?

After consulting with the radio manufacturer about a setup for my FSK radio module (HM-TRP), they have suggested I program it with the following values when setting up the module for 115kbps: ...
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1answer
41 views

ramp-up “guard” time (data receiver)

I have looked at multiple datasheets of multiple radio modules including one I'm using (HM-TRP) and none of them specify a ramp-up or a ramp-down time. According to research, this is known as the ...
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2answers
161 views

What does it mean to “swamp” a radio signal?

Context: It frequently happens that when a particular brand of RC transmitter and receiver are too close (within a meter) the two units lose connection. The recommended fix (which works) is to move ...
37
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3answers
5k views

Why do IR remotes influence AM radios?

When I put my IR remote near any AM radio and push any button on the remote, I can hear a sound from the radio speaker (like beeping). This phenomenon is very weird for me because the radio has no IR ...
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1answer
263 views

Discrete component FM radio receiver circuit - explanation needed

I have built an FM radio receiver from a kit. I'm very happy with the results! It is the Sinclair Micro FM. My goal is to learn about discrete electronics (NO IC's.) The radio works great, but I ...
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1answer
75 views

Tech help with story: Will my radio signal be blocked by a mountain? [closed]

Hoping I can get some help with a technology question for my novel. My protagonist is being pursued, and they have put a tracker in his arm he cannot remove, lest it blow up and kill him. Pretty ...
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0answers
87 views

What RF frequency can I freely use without a government's permission legally?

So I want to create a transmitter that sends digital signals that have 30 kilometres of range but in my country. Radio transmission without authorisation is only allowed upto 50 metres. I researched ...
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1answer
143 views

What modulation is this?

I'm currently learning about signal modulation and fail to figure out the modulation of this signal - maybe someone can help me with it? The software is GNURadio and the device capturing the signal ...
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1answer
32 views

Would multiple radio repeaters experience feedback or interference from eachother?

I'm creating some sensors that repeat each others' audio feeds over radio in a point-to-point fashion in order to listen much like a distributed baby monitor. Each sensor has a circuit for a repeater ...
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1answer
67 views

Gain of a Dual Gate MOSFET

simulate this circuit – Schematic created using CircuitLab This is the schematic of the circuit but tried to find the gain of this circuit, assuming 50 % of the Duty Cycle for the LO, and M2 ...
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1answer
285 views

Can someone explain how this Ratio detector circuit works?

I understand how a Foster Seeley discriminator works, but in this Ratio detector, which is a modified version of the former, I don't understand the purpose of having three transformer windings, or ...
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0answers
25 views

Radio emission: Which bands of a GSM/LTE module to test (FCC)

I am a developer of an IoT-product that is (almost) ready to be introduced to the market. For data communication, we're using the SimCom SIM7000G which provides access to the cellular network in ...
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0answers
42 views

How to measure noise on an antenna in system

I am working on an antenna based RF receiver (AM/FM radio) that appears to be picking up interference from other parts of the circuit. I want to view the noise spectrum, but the receiver chip doesn't ...
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0answers
42 views

FCC EIRP test results different than other countries

We have an issue with regulatory testing where our lab reported EIRP varies significantly between separate labs who have tested for FCC and another country. The test methods are quite different. The ...
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2answers
92 views

Is a coil FM transmitter frequency affected by my body static?

I've built this coil FM transmitter following these guides which are essentially the same: https://maker.pro/custom/tutorial/how-to-make-an-fm-transmitter https://www.instructables.com/id/The-...
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3answers
87 views

How does a crystal radio headset act as a lowpass filter to remove the carrier wave.?

I saw a similar question " How can a diode act as a detector in a crystal receiver" but one of the comments said "after the diode splits the wave form to the top half ...the carrier must still be ...
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4answers
248 views

How can I record RF?

For audio I can use just sound card, plus OS api to record any signal from 20 hz (below that's blocked via capacitor) to 96khz(that's half of max samplerate). But what if I just want to go higher? As ...
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2answers
432 views

What does the wifi amplifier exactly amplify?

The question is not exactly about the wifi, but on how does this operate in full duplex, in principle? As an practical example, lets take some commercial amplifier. As we can see from the picture, it ...
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2answers
228 views

AM Radio Wave LED Indicator

I recently learned about simple AM transmitters and receivers. Now, I'm trying to apply this and expand my understanding by trying to create an AM radio wave powered LED. I'm a very beginner ...
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3answers
159 views

Why do carrier waves sound silent on radios?

I was recently reading about and building low-power AM radio transmitters, and read/noticed that when the carrier wave is not yet modulated, the radio receiver goes silent. For example, let's say my ...
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1answer
75 views

Long Distance High Speed Wireless Data Transfer

What kind of device can I use to transmit data at a rate of 1MB/min up to a distance of 100 miles? If that's not possible, what's the farthest distance to which I can transmit the data.
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2answers
60 views

Determining whether signal meets the 12 dB SINAD voltage

The specification for the sensitivity of a certain radio receiver says: Typically 12dB SINAD NBFM for 0.15uV at 145MHz. If I understand correctly, this means that the received radio wave should have a ...