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Questions tagged [radio]

Radio is the technology of signaling and communicating using radio waves. Consider using the rf (radio frequency) tag.

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How exactly does RF to IF conversion work in an AM radio?

I am currently researching AM radio detection circuits. From my understanding, RF is received, amplified and converted to an IF(455khz for AM) before being converted into an audible frequency for ...
lemon's user avatar
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1 answer
37 views

P2P communication: maximum range for low power & low bandwidth

I've started a little side project with the goal of tracking my cat's location in real time. To transmit the GPS-data, it seems like I have two options: I can either use cellular communication or (...
bns's user avatar
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1 answer
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Accessing the FM 19kHz Pilot?

How can one attach an oscilloscope probe to the mono mode output of an FM station to pick up the 19kHz pilot (normally used for stereo)? Is it expected that FM tuners such as the RDA5807 will, in mono ...
James Bowery's user avatar
4 votes
3 answers
477 views

Audio engineering: amplifying two different sources

I've started a small project to renovate/rebuild an old record player for my wife. I have a degree in Electrical Engineering, but it's been almost 15 years since I last had to project/build a circuit, ...
Yuri Oliveira's user avatar
-2 votes
4 answers
117 views

How can an audio signal with varying frequency be modulated using FM? [closed]

An audio signal can have varying frequency and amplitude and both are the part of the information. As I understand it, frequency modulation is a technique where the frequency of the carrier wave is ...
Ritam Sarkar's user avatar
2 votes
0 answers
75 views

how do tube filament resistors work on this Type 10?

picture source: "Building a 1929 style TNT Transmitter", The VE7SL Radio Notebook, 2009 https://qsl.net/ve7sl/tnt.html, originally referenced from the 1929 ARRL Handbook I don't know how ...
DeWitt2967's user avatar
-1 votes
1 answer
47 views

Sending control signal via FM

Is it possible to send different signals to a receiver using FM which then the receiver would be able to distinguish between and do a set act based on the signal? How to? For example, the transmitter ...
adam_Barfi's user avatar
1 vote
1 answer
64 views

Crystal radio antenna question

I am trying to make crystal radio. I have almost everything I need (magnet wire, high impedance headphones, germanium diode.) The only thing I am missing is the antenna. I know that if I want to ...
LaCalienta's user avatar
-1 votes
4 answers
117 views

Why do we need a diode in an AM demodulation circuit?

The incoming signal is a modulated carrier wave, right? If we only apply a low-pass filter to it, we will get an AC signal that can be passed to a speaker directly, right? Using a diode, we end up ...
Coykto's user avatar
  • 101
1 vote
1 answer
60 views

Wideband Dipole Antenna Ideas

I am home brewing an FM radio and have this so far. It works great for stations within +-5 MHz of my antennas resonance, but I want to hear more stations farther away on the spectrum. For this reason ...
Yousif Alniemi's user avatar
-1 votes
2 answers
88 views

Why can I hear a radio station when probing with oscilloscope? [duplicate]

I assembled this on a breadboard: and am hearing a faint buzzing sound... My first question is, what could be causing this sound? It does not go away if I connect VIN to ground. With or without VIN ...
brooksbp's user avatar
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Difference between radio transmitter roll-off and bandwidth-time (BT) product

For any radio transmitter, the output signal will likely have a shape filter to manage bandwidth. However I am struggling to understand the relationship between a roll-off (e.g. 0.35) and a bandwidth-...
toddy's user avatar
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17 votes
5 answers
3k views

Can two interfering light beams create radio waves?

Two sound frequencies differing in only a few hertz can create ‘beats’ and this has been popularized in music designed to produce ‘binaural beats’. Can two lasers be tuned in a similar fashion so that ...
aquagremlin's user avatar
2 votes
1 answer
94 views

How to terminate a monopole antenna

There seems to be some debate on emphasizing the importance of impedance matching for maximum power transfer vs maximizing signal to noise ratio with receiving antennas. Some vote for one, some state ...
Yousif Alniemi's user avatar
0 votes
1 answer
48 views

How many independent test transceiver modules are truly required for MIMO testing?

In most if not all of the app notes I have ever seen from the major test equipment vendors, such as R&S and Keysight, it is strongly implied if not explicitly stated that in order to do an NxN ...
user12345's user avatar
4 votes
3 answers
156 views

Do sidebands exist physically?

This is a concept that has puzzled me for a long time: from the Wikipedia: "In radio communications, a sideband is a band of frequencies higher than or lower than the carrier frequency" My ...
ribosoma's user avatar
3 votes
3 answers
227 views

Must LC resonant frequency be identical to oscillating frequency in RF circuit?

I am developing an RF circuit for 503.3 MHz. It will be an AM RF transmitter. The LC circuit I built into this circuit consists of L = 0.1 μH and C = 1 pF. The carrier frequency which carries the ...
user avatar
8 votes
7 answers
3k views

Why does this AM radio circuit not work?

I have been trying to make an AM radio over the last couple days and am very confused as to why this circuit is not working. I found the circuit on this website and I saw this video on this design. I ...
Marcus Marchese's user avatar
0 votes
1 answer
50 views

Rewinding a Tecsun AN-100 MW antenna for LW application

The antenna has a diameter of 23cm. It is 0.8mm diameter wire, with a total of 30 turns. The primary winding is 360 µH with a variable capacitor for tuning with a capacitance between 5.3 pF and 280 pF....
Alexander Gräf's user avatar
1 vote
1 answer
148 views

Is it possible to receive an FM signal without a tank circuit?

I was broadcasting FM signals at MHz frequencies in my room. I know that an AM radio will not work to receive FM transmissions. The special issue is that an AM radio can get any AM signal without a ...
user avatar
0 votes
1 answer
49 views

Piezo electric buzzer as a crystal earpiece? [closed]

Making a foxhole radio, saw on https://rimstar.org/equip/crystal_earphone_earpiece_for_crystal_radio.htm can you actually use a buzzer as a crystal earpiece?
Phineas Haskell's user avatar
1 vote
2 answers
249 views

How can VHF signal be amplified with respective gain by simple BJT circuit design?

I am studying RF amplifiers. Most of the time, when I simulate several BJT amplifiers at a very high frequency, I do not get a good voltage or current gain. I have heard of Miller effect. What does it ...
user avatar
3 votes
2 answers
304 views

Why use a loopstick rather than a choke for MW radio frequency reception?

For reception in the medium wave range (500-1600kHz) a ferrite rod (loopstick) has a measured inductance of Lc=2mH and a resistance Rf=5 ohms, whereas an RF choke with Lf=2mH has a resistance Rc=8 ...
James V Stone's user avatar
0 votes
0 answers
98 views

Problems with regenerative receiver circuit

Im trying to build a regenerative receiver, that is supposed to receive a ASK/OOK modulated signal. but there are a few problems. Keep in mind this circuit might be horrendous, but it's just a proof ...
Allfadern's user avatar
-1 votes
2 answers
153 views

Where is the transmit power of antenna in RF circuit schematic calculated?

I want to measure the transmit power of my AM modulated RF circuit. Below is the RF circuit from LTSpice. Should the power be calculated at nodes R5 or C3? Which node can serve as an antenna? The ...
user avatar
1 vote
2 answers
290 views

Why won't the TL084 amplify the RF output of a tank circuit?

Specifically, if a circuit can amplify a 10mV (10kHz) injected sinusoidal signal to about 6V, why does it not amplify the 10kHz RF output of a L-C tank circuit? The tank circuit below has a resonant ...
James V Stone's user avatar
-2 votes
4 answers
102 views

RF signal chain gain

In conventional electrical signal chain design, we now exactly what is the amplitude of signal in any node, from source to load. In radio frequency circuits which contains antenna. We don't know the ...
mohammadsdtmnd's user avatar
1 vote
2 answers
73 views

Wi-Fi radio without an antenna [closed]

I'm mostly unfamiliar with radio, but I've read that you will eventually fry a transmitter if you operate it without some kind of antenna or at least a dummy load attached to it. The question is ...
user1686's user avatar
  • 115
-4 votes
1 answer
103 views

I am trying to building an AM radio using SMD components [closed]

I have a lot of SMD components, and I would like to build an AM radio using these components. I tried to search for radio circuit SMD, but doesn't exist. Is it possible to do so?
Felipe Lima's user avatar
1 vote
2 answers
88 views

Ferrite Loopstick Antenna Grounding

I've built a simple tuned frequency radio based a description in Ronald Quan's book. I have two questions about the tuning part of the circuit. The radio has a ferrite core antenna with two separate ...
M. Enns's user avatar
  • 113
0 votes
2 answers
238 views

Does adding DC offset to RF output signal affect the range of RF transmission?

Does adding DC offset to AC output signal affect the range of RF transmission? Adding DC offset does not magnify the AC signal, it is just an offset with more power for the output. I had once asked a ...
user avatar
0 votes
1 answer
70 views

What is this type of radio aerial called?

I need a replacement aerial for my FM radio, but I can't seem to find the right type. I suspect that this type of aerial has a name. It's telescopic, and has a joint so that you can angle and rotate ...
Rocketmagnet's user avatar
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1 vote
0 answers
57 views

Soldering the AUX IN cable to the JVC KD-161 radio

I soldered the AUX IN cable as in the diagram, added capacitors. In the diagram, pin 4 is GND. I insert a CD with a silent recording and unfortunately nothing comes from the smartphone. I will add ...
Mikolaj's user avatar
  • 11
2 votes
2 answers
185 views

How can a Faraday cage absorb and reflect waves, yet antennas mostly absorb and can be used on signals?

I understand they are very different in structure but comparing a simple monopole to a Faraday cage, they both are constructed from metal. Why is it the sides of the Faraday cage absorb the waves and ...
George kirby's user avatar
2 votes
3 answers
114 views

Why are signals reflected from an antennas dish as opposed to being absorbed?

I am trying to learn in the area of electromagnetic noise ect. I see online that a Faraday cage can work without been contected to ground (like the ones found on radio PCBs.) It sort of makes sense to ...
George kirby's user avatar
0 votes
1 answer
125 views

SRIX4K Emulator - ASK transceiver

I'm trying to build a simple SRIX4K emulator using an ATMEGA328p, I found this circuit on the internet, and it should work as a simple ASK transceiver, using the MCU to transfer data using the SRIX4K ...
Giovanni Visentin's user avatar
0 votes
0 answers
45 views

Does the law of reciprocity hold true for the phase response of an antenna?

I know that an antennas spectral transfer function should be the same in both transmit and receive due to the law of reciprocity, however does this law hold true for the phase response (AKA phase ...
Christian's user avatar
  • 105
0 votes
1 answer
258 views

Demodulation of FM signal frequency

After playing with homemade AM radios, I noticed that it is boring to broadcast AM signals all alone. I have also noticed that the AM stations around us, are so limited that I had no other chance than ...
user avatar
2 votes
0 answers
81 views

Review of PCB RF Design

I designed a 4 layer RF board with the NRF24L01+. When I got the boards in to test I was not able to establish a radio link with some other NRF24L01+ modules. I have attached my schematic and board ...
M.Schindler's user avatar
0 votes
3 answers
306 views

If my radio is tuned to a slightly different frequency, should the audio be largely inaccurate?

So we may have a radio station on AM 1400, or AM 1450, or it can be FM 96.5 or FM 98.1. My question is, it seems the "1400" means, we pick up a signal (either 0 or 1, or an amplitude) every ...
Stefanie Gauss's user avatar
0 votes
0 answers
66 views

NF (Noise Figure) calculation - task

In a 622 Mbps radio-link interface, it was assumed that the BER would be 10^-10 when the signal-to-noise ratio at the receiver point is 7.8 dB, while its sensitivity for a fixed modulation-code scheme ...
airborne's user avatar
0 votes
1 answer
63 views

Debugging an automotive FM transmitter

Transmitter is a 12V automotive audio-to-FM transmitter unit. Belkin Tunecast F8M066. Receives both power and audio fine over the cables into the unit as measured on the board. 7.6 MHz crystal is ...
Reinderien's user avatar
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-1 votes
1 answer
141 views

Is this circuit for attaching an amplifier to crystal radio going to work? [closed]

This is a circuit I created and I was wondering if its going to work, by the way I am new to electronics so if you see any obvious mistakes please let me know.
Mr.Ananas's user avatar
2 votes
1 answer
250 views

Would this crystal radio circuit work?

Would this crystal radio circuit, that I came across, work? If it would not work, I would like to know which part of the circuit could be the likely cause and why. The speaker shown is actually a ...
Mr.Ananas's user avatar
1 vote
1 answer
86 views

Name for this kind of mixer?

I am trying to learn how a gilbert cell could be used as an amplitude modulator and tried to simplify its operation by assuming single ended inputs. While trying to visualize some concepts I ...
Yousif Alniemi's user avatar
2 votes
0 answers
195 views

How to calculate an rf amplifier stage

I changed the LC tank of the circuit below for operation in the 2m ham radio band (144-146MHz, I'm a licenced Class A Ham). Now I'd like to add an amplifier stage to increase the output by about 30dB. ...
Laurin's user avatar
  • 21
3 votes
2 answers
2k views

Understanding FM Broadcast Receiver with RDA5807FP

I've been trying to build an FM broadcast receiver for the last few weeks know, with simple designs like with LC circuits, but I've realized that an IC based radio outperforms simple transistor radios....
Charlie Nicholson's user avatar
0 votes
0 answers
39 views

Toroidal/cylinder single turn transformer to circular waveguide coupling

The questions is mostly in the title. Is it possible to effectively couple a toroidal/cylinder shaped ferrite core with thick spread out single turn of wire to a circular waveguide? The idea is that ...
Girts's user avatar
  • 31
1 vote
1 answer
208 views

GPS signal combiner

I want to use WP4N+ as a GPS signal combiner with NEO 6M receiver. Here is my schematic. On power on, resistor 22 Ω is getting VERY VERY HOT and I do not receive any signal from the satellites. ...
Alatriste's user avatar
  • 160
0 votes
1 answer
347 views

How to make very low range FM Transmitter?

I am experimenting with building an FM transmitter. I want to make it only have a range of a few meters so I can detect it on my radio at home at a distance of a few meters. The circuit diagram is ...
LEXOR AI's user avatar
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