Questions tagged [radio]

Consider also the rf tag.

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1answer
81 views

Why do so many crystal radios have big coils?

I've been looking at crystal radios recently, and I noticed that many of them had quite big coils (maybe around 5cm on average from what I can see), but wouldn't they want quite a low value inductor ...
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0answers
47 views

Radio - Amplifier Connection

This is my first post here, so please give me feedback on how I can improve in the future. Background I am trying to reverse engineer a Becker Grand Prix Stereo Radio with an external amplifier. On ...
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4answers
170 views

How to demonstrate mathematically the conditions of reflection in transmission line?

We are all taught about transmission lines and its associates -- characteristic impedance, reflection, standing wave, etc. It is well known what happens when a transmission line is terminated with ...
5
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2answers
378 views

Reading an Old Philips Radio Manual with SCR rows

I've been looking at the manual for the Philips L4X26T radio and I have noticed that for each of the diagrams, there is a rather peculiar table with three rows of numbers labelled "S", "...
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3answers
11k views

Modify an AM/FM radio to an airband receiver: What, if any, changes to the demodulation circuit?

It seems to be possible to modify a cheap AM/FM radio to receive air traffic control (ATC) communication just above the regular FM band. One range used for ATC is at 108...137 MHz. Some quick ...
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0answers
62 views

Connect headset to radio

I would like to connect a headset to my radio (Cobra AM845.) The Cobra radio has a 2,5mm audio jack and the headset has a 3,5mm audio jack. I made a PCB to connect the together as: When I close ...
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0answers
102 views

Will a jammer operating at a certain frequency block both AM and FM signals?

I am planning to build a signal jammer with a very short range just to protect my devices, e.g., phones, computers from possible covert channels using radio signals. Depending on the malware being ...
0
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4answers
57 views

Signal interference in receiving antenna?

I’ve been scouring the interweebs for some insight into how electrical signals travel in a wire. More specifically, I cannot wrap my head around how a receiving antenna works with hundreds if not ...
0
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1answer
304 views

Determining the bit rate on a real-time USRP implementation

I'm transmitting a 16-QAM signal using an NI 2920 USRP. Here is a snapshot of the front panel that is seen (on LabVIEW) - I'm trying to figure out the bit rate from the given details. The symbol rate ...
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3answers
123 views

Troubleshoot DIY AM radio

I need help troubleshooting my DIY radio. I am following the schematic this link. See pictures below for a diagram of how the components are wired and the actual wiring. The design I made is different ...
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2answers
1k views

What Makes a Radio Transmitter Powerful?

I've been doing research on radio transmitters, and though I understand how the signal is generated and how data is transmitted, I still can't understand what defines a radio's transmitting power. How ...
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1answer
52 views

433 MHz Transceiver - understanding OOK demodulator parameter 'OokFixedThreshold'

I would appreciate some help to understand a parameter for this device https://www.semtech.com/products/wireless-rf/fsk-transceivers/sx1231h. I'm far from an expert at RF matters and this question has ...
6
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3answers
651 views

How does someone design a low frequency FM radio transmitter?

I'm relatively new to the topic but I'm intending to transmit some data from a measurement system in a cave to a receiver on the surface. I understand that I can use a SDR (software defined radio) to ...
0
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0answers
65 views

Design of a low frequency (80 kHz) voltage-controlled oscillator circuit

I'm working on a project involving low frequency, through-the-earth data transmission from a transmitter in a karst cave system to a receiver on the surface. I've worked out that a SDR can be used for ...
0
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2answers
181 views

Name of an electronic component

Can anybody kindly tell me what this electronic component in the picture is called? I've seen this component in: Mobile phone circuit WiMax modem circuit GSM Module circuit I tried but was unable ...
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1answer
31 views

Radio receiver output selector [duplicate]

I have been given this project for my second year electronic. I have to make a circuit which has 3 audio signal inputs of different shapes like sine, square and triangle waves. The output has to be ...
19
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3answers
11k views

Can I break a radio tranceiving device by operating it with no antenna connected?

People tell me I shall not use my CB-radio station without an antenna connected or it will result in damage of the device. Is this true and why is this?
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56 views

CB Radio Effects Unit. Can anyone help with a wiring puzzle?

I’m working on a small CB radio project for a friend, but am having a hard time figuring out some technical details. If anyone has any ideas on how to solve this puzzle I’d be super grateful. The ...
0
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1answer
89 views

Figuring out what this circuit does

I need to understand this circuit (at least to a basic point). I know it's supposed to be a radio but I need to break into stages in my head to get what's happening. I am going to try to describe it ...
2
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0answers
119 views

Ratio detector FM demodulator

The aim of the exercise is to design a ratio detector FM demodulator circuit. UPDATE: I changed the circuit: This is my transient analysis in output: I found the information about AC analysis and ...
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0answers
13 views

How do i find the FNBW of a main lobe using a diagram?

Looking at the graph below, i can see that HPBW of the main lobe is around 45 degrees, but when it comes to identifying the FNBW i have trouble understanding it. Reading various articles online i've ...
11
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2answers
5k views

Why are radio signals clearer near the human body?

In Asia, specifically in Bangladesh, we often listen to FM radio. But the signal is not clear everywhere, that means it produces some noise. From my childhood till today, I have observed that, if I ...
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1answer
68 views

Watt output of radio station

I was wondering how many watts an AM radio station outputs, and if I can calculate the watts on a tuned antenna by this equation: Where Win = the watts input for the antenna, Wout = the watts output ...
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2answers
109 views

What makes it hard to build a powerful RF transmitter?

I was looking for a powerful RF transmitter lately but I didn't find many. They are low power (< 0.5W) or expensive. I have a little understanding of a regular 433MHz transmitter's schematics. It ...
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4answers
66 views

Negative resistance in a regenerative radio receiver?

Why is an amplifier with a tuned circuit and positive feedback, such as a regenerative radio receiver, said to exhibit or have negative resistance?
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1answer
182 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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2answers
2k views

Where is the antenna in this remote control board?

This is a PCB of a (radio?) remote control.
0
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1answer
81 views

Is this a demodulated signal?

1st attempt I have a problem. I built the FM demodulator circuit, but i am not sure if this signal is demodulated. This was my first attempt which following an answer, resulted in a 2nd attempt ...
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1answer
70 views

How does my 802.11 a/b/g/n wireless card determine the modulation to use?

I was thinking yesterday about how the 802.11 a/b/g/n standards all use different modulation schemes, but my wireless card manages to detect frames from networks that may use any of those modulations. ...
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2answers
167 views

With so much radio signalling occurring simultaneously (TV, Cellphone, Radio, etc.), how does our atmosphere keep them separated and avoid disruption? [closed]

I know this question has been asked before, but I still don’t completely understand. I understand that different stations are given different frequencies, but waves are able to interfere with each ...
0
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1answer
408 views

QUCS simulation radio transistor amplifier

I'm trying to design a small amplifier for AM signals to use before the usual diode-C-R detection (the reception in my area is very poor). I devised a QUCS simulation as below: The diode and ...
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2answers
40 views

What is the irregular signal at the bottom of this “spectrogram”?

I am reading research papers about LoRa, and I have come across the below figure in this one. The horizontal axis is clearly labeled frequency, but the vertical one isn't. I recognize the chirps in ...
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1answer
236 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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0answers
62 views

How does one choose a resistance for an AM radio antenna receiver tuner?

[![enter image description here][2]][2] I am using some pretty rough, brute force and novice calculations, so if anyone knows a nicer method I am happy to learn. I want to build an AM radio receiver ...
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0answers
49 views

TTE low frequency radio transceiver

I'm interested in developing a bespoke through-the-earth (TTE) radio transceiver for a measurement instrument in a limestone cave system. The issue I have is that conventional RF signals cannot ...
2
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2answers
461 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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1answer
106 views

Using Clear Channel Assessment / CSMA in CC1120

I have two transmitter nodes both running the same firmware, just that the transmitted packet is configured to have a different node ID (you can call MAC address) in it's packet. I see that the ...
1
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4answers
894 views

What are the basics I need to know to power LEDs with RF at a range of 30 feet?

I would like to light up a path in the woods with hundreds of LEDs using RF. The idea is that I would carry a RF transmitter powerful enough to light LEDs. As I approach the LEDs would get brighter, ...
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0answers
74 views

'P.V.' marking on 1940's electrolytic capacitors

I am replacing the paper and wax capacitors in a tube radio of 1949 vintage. Puzzled by the initials P.V. where I'd expect to read VAC or VDC. Can anyone explain this puzzling jargon? For some reason ...
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1answer
68 views

Is it true that FPGAs and DSPs are widely used for modulation and demodulation of signals? [closed]

I have to write a thesis about digital communications, and I don't want to write something stupid in it. I also wrote that "most of the digital modulations and signal processing nowadays are done ...
1
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1answer
46 views

Formula to calculate the isotropic range of a signal

I am wondering, is there a formula to calculate the range of a signal with a given frequency and output power? For example, how do i find the range of a 580khz AM signal on entirely flat terrain with ...
4
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2answers
415 views

How to properly layout an external antenna seating and on board antenna at the same time?

I want my board to have the ability to opt for either an onboard antenna or an external one, with a 0R chip resistor, naturally. This is my initial setup: But then I am told that this is flawed and ...
0
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1answer
37 views

Modern substitute for BF494 or 2n3707 transistors

This question has been asked before, here: https://electronics.stackexchange.com/a/263366/199668 But since it's been almost 5 years since that post, does anyone know any substitutes for the mentioned ...
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3answers
108 views

Noisy AES audio signal in studio installation

This is a question about digital audio cables. I know this isn't an audio engineering forum but the question's specific to the physical connections and there's limited info online which I can find ...
0
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1answer
131 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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0answers
13 views

Split loop cavity or Loop gap cavity

I want to make a code for the power vs wavelength for the split loop cavity resonator. Can someone help me with the python code for the same?
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6answers
6k views

MIMO: How Can Two Antennas So Close Together Receive Different Signals?

I'm trying to understand how MIMO (as used by 802.11n wi-fi and some upcoming cellular data standards) works in practice. I understand at least the gist of the theory of spatial multiplexing. What I ...
9
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3answers
1k views

Hearing only noise and ticking sound with simple AM radio - The art of electronics

I've tried to build the simple AM radio that is proposed at page 56-The Art of Electronics (3rd). The idea is to tune my radio on a frequency of 657 kHz (I'm sure there's a station at that frequency)....
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1answer
100 views

Do AM radio broadcasters pick frequencies that are picked up as interference on purpose? [closed]

This is not meant to be a political question, rather a historical one, USA based. Every place I have lived, if I have an amplifier with a long enough input wire, I will start picking up AM radio if I ...
1
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1answer
107 views

Vintage Pocket Radio Transistor Replacement is Oscillating

I have an old pocket radio which uses silicon NPN transistors for the mixer and IF stages. I replaced 2 of the IF transistors and the unit functions, but the new transistors are faster than the old ...

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