Questions tagged [radio]
Consider also the rf tag.
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sr-t500 walkie-talkie module [closed]
I have the sr-t500 walkie-talkie module.
Everything works fine, but the sound is not sent through the microphone!
I tried replacing the microphone, but there was no change.
Does anyone have ideas ...
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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 ...
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Calculation 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 ...
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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 ...
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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 ...
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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 ...
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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 ...
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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.
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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 ...
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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 ...
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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.
...
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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....
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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 ...
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96
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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. ...
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178
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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 ...
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Can two or more RF noise signals (or noise sources) still be added together if they have been attenuated below the thermal noise floor?
Can two or more RF noise signals (or noise sources) be attenuated below the thermal noise floor, and still add together to be higher than TNF?
If a noise signal experiences path loss or attenuation ...
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Advice on measuring relative speed and position of an active transmitting and reveiving object
Using multiple transmitter/receiver stations on ground and the doppler shift to measure relative velocity and position of an airborne active receiver/transmitter in low altitude (0-2 km).
I want to ...
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Radio signal strength or frequency to determine absolute position of a reciprocating system?
I have a highly constrained mechanical system consisting of a bar that moves along a straight path for a distance of 40', reciprocating 7 times a minute.
I want to determine the position of the bar ...
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What is the purpose of the choke inductor coil in this qrp radio transmitter?
After building and testing these circuits, I want to understand the purpose of the choke coil in these qrp trans(ceiver)mitter circuits.
https://www.qsl.net/py2ohh/trx/curumim/curumim.htm
I ...
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Where does the power go that would have been dissipated once an impedance matching network is in place between say a source and antenna?
If a load (say antenna) was to be physically difference in impedance to the load, so you decided to place a sort of matching network to match the impedances, where does that now unreflected power go, ...
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MICOM 3F VR1 part
It is marked with a circle and ON in the middle. then you can see SR wrapping around the sided but the bracket is in the way from there. on the other side you see 467 SK0 but then the oppisite bracket ...
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101
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How to calculate the voltage and / or current in a crystal radio?
I have thought of using V=E*d for the voltage across the antenna (d being its length and E the electric field strength of the incoming radio wave) and then use I=V/Z with Z being the total impedance ...
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Is there a (legal) wireless transmission solution for my underground parkade anti-theft alarm?
I live on the 4th floor of a low-rise condo building with a concrete parkade beneath. We have a serious problem with bicycle theft -- someone is coming in late at night with an angle grinder, and ...
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RF shield mesh rules of thumb
When you place a RF transmitter within a metal enclosure with openings that can be approximated as a mesh, are there any rules of thumb for either letting the signal pass through or get attenuated?
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Calculating for impedance matching of more complex circuits
When I start off to calculate the impedance from Z-input, how can I reach to antenna's Z-output which may be variable, for example 50 ohm.
I have several good links on Internet:
https://www....
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Spooky multimeter AC reading using 1 lead
I'm fixing an ultrasonic cleaner board that isn't working. There's a small transformer that drives the transducer. When I set my DMM to AC and touch both leads on its output, there's no reading. If, ...
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AM radio using a quartz crystal and a dipole antenna
I have been on the look out for AM radio circuits on the internet.
The ones I have come across are circuits using monopole antennas and LC tuned circuits.
However, I require a circuit using a quartz ...
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What Capacitor do I need? (if any) [closed]
I have a airplane with a radio and other electronics. When I transmit on my radio the voltage drops about 0.3 volts across my other electronics and causes some sensitive sensors to read incorrectly. ...
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Is it possible to design an antenna with constant antenna aperture (that doesn't vary with frequency)?
As per the title, I'm interested to know if it's possible, either theoretically or practically, to have an antenna design which has a constant effective aperture (antenna aperture - these are the same ...
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How far could I pick up VHF from?
I’m new to electronics but I'm doing my ATPL pilots license soon and am interested in the EM spectrum and in particular, radio waves. I was wondering what factors affect the maximum distance I could ...
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Why would 50W of power be sent to be reflected in the first place to an open end antenna port to be reflected [duplicate]
I understand theres a lot online about transmission line theory it terms of why the reflection, but if say the load was open or really high, thinking of a standard circuit, the total series inpedance ...
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My RF amplifier circuit works in LTSpice. Will it work in reality, too?
I am working now for a while with bias calculations. I have found a good turorial to calculate it by my own and I have seen that there are already calculators on internet, which made my life much ...
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Is it possible to use RF signal wires to let a model car center itself on it using phase differences?
I'm looking for a way to let a model car (1/24 to 1/18) know how centered it is on a road. I thought about using a buried wire in the middle of each lane of the road. Would it be possible to detect ...
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Can I use an SDR to transmit on the ISM band without a license?
I would like to use my SDR to transmit arbitrary data.
Can I freely transmit in the ISM bands without any license, as long as I abide by the regulations? My understanding is that I can transmit at up ...
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Basic RF signal amplifier
I made an 8 Mhz shortened antenna with a length of 12.3cm and wire diameter of 2mm by a 220uH bobin at the bottom. The transmitter and the receiver circuits have the same antenna configurations. The ...
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Charges in receiving antenna and polarization if alternating current is changed to stay high
A dipole antenna receiver placed in parallel to a dipole antenna transmitter will have a current induced in the opposite direction to the current in the transmitter. This causes charges (electrons and ...
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Is there a RadioHead library equivalent for STM32CubeIDE?
I have been using the RadioHead library for Arduino with devices such as RF95 and RF69, and have found it very useful for simplifying device interfacing (i.e. removing the need to implement all of the ...
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FSK modulation and inverting mark and space bits
Quick theory to application question.
In Frequency shift keying we usually have the output of a sequence generator into a VCO, then this leads to a high frequency for the mark bit and a lower ...
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BL654 Bluetooth module Tx power issue
I am working on the BL654 module, and as per the datasheet, max Tx power of the module is 8dBm. But as per measurement, I found near to 6dBm power. Is there any issue regarding the power limit or ...
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Which is correct in regards to an antenna: effective aperture is a function of wavelength, or gain is a function of wavelength? Or both?
I understand why the effective area of an antenna is related to the wavelength. I'm aware of the below equation:
$$G = \frac{4\pi A_{eff}}{\lambda^2}$$
However this suggests to me that one of either ...
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How can I only let a specific frequency pass in an AM receiver?
I wanted to create an AM receiver and I know partly how to demodulate the signal. I know I need to use a low pass filter to get the low frequency audio signal, but I don't know how to only get data ...
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How to tell the needed power source for vintage tube shortwave radio?
This might be a long shot on this forum, but I’ve got an old shortwave radio with tubes, and I’d like to power it to try it out.
How do I determine what is the input source it expects? The input wires ...
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102
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Weird component in radio player interferes with FM functionality of the radio itself
I got my hands on an old radio player which has both cassette player and FM/AM functionality. I got constant noises while playing on FM and it turns out to be some weird component on the cassette ...
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How to connect LoRa antenna and RP-SMA to U.FL to RFM69HCW?
I want to use this radio module and this antenna and this extender for my diy RC. Is this possible, and how would I connect the extender to my radio module? Can I cut the U.FL side and solder them ...
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WWVB receiver design advice [closed]
I am completely new to the world of amateur radio and I'm attempting to make a WWVB receiver and antenna. I currently have a large ferrite loopstick antenna built, based on this video.
I got a ...
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120
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Help with PNP transistor schematic
I would like to build a FM radio reciever with PNP germanium transistors but I can not find a simple yet efiicient schematic for this. Does anyone know of a schematic I can use?
I have found one ...
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Capacitor for quartz crystal in harmonics
I saw a FM transmitter radio circuit, which was an easy one and had a 20 MHz quartz crystal, on internet. It promised to fix the frequency at 100 MHz. I soldered the components together and tried at ...
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Sharing BJT bias resistors
I am designing a radio and realize that I have many of the same BJT circuit blocks that are biased with the same resistor values.
Can I simplify construction by having a "bias line" that I ...
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RF preamp, or no RF preamp?
Frequency downconverters are required to test devices that operate in the range of microwave and mmwave. I have noticed that some companies use a signal chain that has an RF preamp, and some do not, ...
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Series Crystal Oscillator Amplitude Control
I need a 24 mhz clean sine wave.
I made an oscillator like this and it works, but the bottom of my waveform is clipping. I tried a variable 1k resistor on the output to gnd and can shrink the ...
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