Questions tagged [radio]
Consider also the rf tag.
0
votes
0answers
11 views
Detect signal from different sensor via radio, and communicate between raspberry and Adafruit Trinket Mini - 5 V via radio
I'm developing a system, with a central system where there a lot of sensor directly connected with Raspberry. I need to receive a radio signal from an external sensor, what radio module can I use?
I ...
0
votes
2answers
57 views
Is my radio pulling more current than it should?
I have an FT-747GX radio that I am using as a RF generator for a plasma cleaning machine.
In the operating manual on page 3 it states:
I have a power supply connected to this radio which outputs ...
0
votes
0answers
16 views
What is the use of Level Set and 12AU7 circuit in Pilot FA-540 tube tuner radio?
I recently scored a Pilot FA-540 tuner on eBay. The one I received was from a console. But the models sold usually is the non-console type. So, while going through the circuit from the service manual ...
0
votes
1answer
31 views
run ac device on battery [on hold]
I recently purchased a radio which unfortunately doesn't have battery option. Its spec is AC 230V - 50/60 Hz and 14 W
Is there any way to use my Ni-Mh rechargeable cell battery with this device.
...
-4
votes
0answers
46 views
What amplifier RF do you advice me at low cost to transmit at 82mhz with a power of minimum 50W to 100W? [closed]
I have to transmit a sine wave at 82Mhz and 85Mhz, what do you advice me?
0
votes
0answers
23 views
Unwanted buzzing and reduced volume in a basic speaker set
I have the following device, which basically contains 18 songs. we can play the next song by switching the switch on and off. It also has a volume control.
Recently it started to buzz a lot and the ...
0
votes
1answer
39 views
EN 300 328 CE radio certification with power limit
We have developed product for Malesia country, where we need local SIRIM certificate.
RF module we used in our product is 2.4Ghz wifi mesh, with max 30dbm (1 watt) output power capacity.
To get ...
0
votes
2answers
52 views
op-amp amplifier for small loop antenna
I’m trying to make myself a ferrite core loopstick antenna for a crystal radio project so I’ve pulled the ferrite rod out of an old radio. The rod is about 1.5 inches and I’ve wound my own coil around ...
0
votes
0answers
52 views
High data rate (~1-5 Mpbs) Point to Point Radio
I'm working on a rocket project at my University, and am trying to find a point to point / point to multipoint radio capable of a hopefully 1-5 Mbps data rate between a ground station a directional ...
2
votes
0answers
45 views
2.4GHz RF design losing signal
First time poster here, please excuse holes in the plot.
I have a simple wireless design made of an MCU (atmega328p) and an NRF24L01 module, powered through a 3.3V regulator, talking to a similar ...
0
votes
1answer
82 views
How to increase range of AM radio waves? [closed]
As a personal project, I made a very simple AM transmitter with an idea from an online tutorial, using a 1 MHz crystal oscillator (plus power source, antenna, breadboard, etc.).
However, when using ...
-4
votes
1answer
73 views
Are headphones with EMF measurement of 10,000 milligauss harmful to me?
I used a EMF detector app on my phone and measured the EMF output on my wired headphones. It measured around 10,000 milligauss on one part of both ear cups. Since wearing these headphones on my head ...
0
votes
2answers
170 views
Explain this circuit
I know this circuit is an oscillator circuit and it senses another signal of same frequency, but I don't understand
the calculation behind it, and
the reason for emitter inductor,
3.9k collector ...
4
votes
1answer
62 views
What kind of modulation technique and carrier frequency is used for interplanetary communication such as between the Earth and Mars? [closed]
I have just come across this wind sound coming from pressure sensor of Insight lander which is in Mars at the moment.
I know basically that AM, FM, PSK, FSK ect. all have disadvantages and advantages ...
0
votes
3answers
64 views
Why does antenna tuner in crystal radio use capacitor and an inductor?
I know that antennas can be capacitive or inductive depending on the relation of antenna length to the \$\lambda\$. I know that crystal radios use both antenna and capacitor for tuning and I don't ...
0
votes
1answer
69 views
Can a speaker be driven by a DC signal?
I’ve always been under the impression that speakers require an AC signal. The reason being that positive and negative current are required for the electromagnet to properly vibrate the diaphragm.
...
0
votes
2answers
58 views
Speaker for crystal radio rather than sensitive piezoelectric speaker Crystal radio
I am a science student of grade 8 and researching and learning about radio waves.
I am currently trying to make a crystal radio. The problem I am facing is the speaker I have to use for the project....
1
vote
1answer
62 views
Other than direct radiation, how can RF interference transfer between stacked PCBs?
I have VHF aviation radio consisting of 3 boards stacked upon each other: digital, receiver and transmitter, the digital is on ‘top’ with receiver in the middle, there is thick shielding between the ...
2
votes
1answer
111 views
Amateur radio practice exam question
The question is as follows:
An interfering signal from a transmitter is found to have a frequency of 57 MHz (TV Channel 2 is 54 - 60 MHz). This signal could be the:
And the options are as follows:
...
1
vote
0answers
52 views
Electro magnetic interference with Arduino Uno and a portable radio
I'm surprised when I'm working with Arduino Uno, by just sitting beside a portable radio, like when I was powered on both Arduino & Radio and when they are close to each other I got some noise ...
0
votes
1answer
38 views
Receiver Antenna Gain
How is gain defined for a receiver antenna?
If we look at a radiating antenna, there is a Pin, and the gain in a particular direction would be the radiation intensity Ur, divided by the radiation ...
1
vote
4answers
110 views
What happens if the frequency of the receiver osc does not match (exactly) the carrier frequency?
I thinking about FM and AM. Theoretically the carrier frequency is perfectly match the demodulation frequency. But what happens if there is a mismatch?
I think using AM the frequency of the base-band ...
2
votes
2answers
87 views
Antenna Design Procedures
I live in a residential area and I want to test and design an antenna in my garage. I plan on using my signal generator as the power supply and a RTL - RDS dongle connected to my computer as the ...
0
votes
3answers
117 views
Voltage gradient across an antenna (and how it drives an AM radio)
Edit:
I was interested how is voltage gap maintained across an antenna. It seemed to me that an antenna might be like a wire where if there's a voltage at the top, the same voltage would be at the ...
0
votes
1answer
46 views
Radio activated on/off switch
TL;DR: I want to know if there is anything, That on which when a radio frequency falls, and it turns on an LED. Basically an on off switch but controlled when radio waves hit it.
What I hope to ...
0
votes
1answer
115 views
What does a TV receiver circuit look like? [closed]
I found a few circuits for TV transmitters, but no receivers.
I've looked at other simpler RF transmitters and receiver, but it's not obvious to me how to reverse the circuit that I have.
I want ...
0
votes
2answers
154 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 ...
0
votes
2answers
162 views
Can I use more than one antenna with a radio module (say rfm69) and switch between those antennas electronically, say by a transistor
I need to know the approximate direction of the radio signal coming to my module, and I have to use very simple hardware and software for this. (Just a microcontroller and one module)
What came up ...
0
votes
1answer
53 views
How does adding more coils to an AM tuner coil allow it to tune Shortwave?
I have seen several tutorials about how to turn an AM radio into a Shortwave radio. They add more coils to the inductor (is that the correct name for the tuning coil?).
Here is one example,
https://...
-2
votes
2answers
102 views
Why FM has larger range than cellular network [closed]
I can receive FM signal about 50km away from the transmitting station but I lose signal from cell towers in about few km (1-3km)
1
vote
0answers
43 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 ...
1
vote
1answer
30 views
Radio Telescope Rx/Tx resolution
Very simple question. If (say) a 65m radiotelescope obeserving at 5cm (6GHz) has a resolution of about 1mRad, if it becomes a transmitter at that frequency does it radiate a beam of the same ...
0
votes
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? ...
0
votes
1answer
120 views
UHF transmitter Range for 50 W
Very curious to know the range of 50 W transmitter of UHF range in nautical miles? The antenna used is 1/4 wave antenna of Jaybeam company. Can someone tell the exact formulation to find out the ...
0
votes
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 ...
0
votes
1answer
60 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 ...
0
votes
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 ...
1
vote
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 ...
0
votes
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 ...
4
votes
2answers
192 views
Is a regulator necessary?
Sorry for the provocative subject line. I was looking at using one of those integrated ESP32 + SX1276 + SSD1306 boards (there are a few that have popped up) in a battery powered application. I would ...
0
votes
1answer
99 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 ...
0
votes
1answer
49 views
How to test an RF crystal oscillator performance integrated into a Cellular radio?
I have a couple of reference designs with 2 different crystal oscillators integrated into it. These are cellular radio and can generate standard LTE QAM signals out of it. But I do not have access to ...
-1
votes
3answers
124 views
Can I apply gorrila glue on to a AAA battery to attach a wire to it? [closed]
I am repairing a old CB radio I got at a yard sale and I'm powering it with 2 AAAs and a 9 volt. I have to attach a wire to all of the ports, and tape isn't very effective. I'm wondering if it it safe ...
-2
votes
3answers
276 views
Radio Transmitter Circuit [closed]
I have seen previous similar answers about radio transmission, but looking at the following scheme I am not sure about the role C3 plays in the circuit. I guess it is needed to remove the DC signal ...
0
votes
1answer
24 views
Regulated power for radio module HM-TRP. Is config correct?
I'm trying to figure out how to make a nice power supply to the radio module HM-TRP.
I heard that running certain voltage regulators with capacitors having high ESR values is a bad idea and will ...
0
votes
0answers
64 views
Crystal Radio Help
Me and my uncle have been working on making a crystal radio for the last few days and have had no success. We have used multiple designs but none of them seem to work. This is the one we've been ...
1
vote
2answers
124 views
Question on Use of Y2 Saftey Capacitor in AA5 Style Tube Radio
In a radio I am restoring, there is a 0.1 uF capacitor between B- and chassis, designated as C12. My thought process is that if this capacitor were to fail, I would not want B- shorted to chassis as ...
-3
votes
3answers
67 views
Use existing WiFi hardware as an RF receiver? [closed]
I have seen mine & many others' (Android) devices nowadays have WiFi hardware capable of connecting with 2.4Ghz & 5Ghz APs. Wanted to know if I could tweak the WiFi driver in the kernel source ...
0
votes
0answers
42 views
Will 2 nearby crystal radios affect each other's strength?
I'm working on a project which involves 2 nearby crystal radios. Their cases almost touch each other. They are tuned at different frequencies. I was wondering if they would affect each other's ...
0
votes
1answer
53 views
Low power local area radio controller chipset [closed]
I have a project where I need to remotely control up to 128 individual relay boards within a maximum 30 meter radius. I need each of these wireless relay controllers to be uniquely addressable to ...
