Consider also the rf tag.

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18 views

Help in finding TX/RX for surveillance UAV FPV in high temperatures and long ranges [on hold]

I'm building a customized ground control station for a surveillance drone. I have four proposed TX/RX frequencies, and the main ones that I need help in is for the pilot and the payload operator FPV. ...
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1answer
52 views

How deep can I bury a 1 MHz transmitter

So in designing a deep underground sensor network, my team wants to use a 1 MHz radio, but we cannot determine a way to model the soil, so as to calculate how deep i can bury a radio for showing proof ...
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2answers
97 views

How can I best fake an (AM radio) antenna signal?

I have an old (~late 1920s) AM radio that I'm currently working on. As I don't want to modify any of the internals significantly, it would be nice to have a way to fake antenna input. It's not ...
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0answers
19 views

RF Propagation of a beacon placed in a narrow hallway

If the walls are sufficiently thick concrete which have very high attenuation, and if the red circle is a beacon/ibeacon with an omni antenna, what is the expected propagation pattern? I want to ...
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2answers
45 views

Band Pass Filters for MHz

I have come across the following site: Passive Band Pass Filter - Electronics Tutorials. It is a tutorial about band passive filter circuits. The following formular is given with: $$ C=\frac{1}{2 ...
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1answer
57 views

How to convert this FM transmitter to receiver?

I made this circuit and it works properly but I need to make an FM receiver using the same idea of this circuit (common base). Would you tell me what changes should I make so that the circuit is able ...
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1answer
63 views

Boost a weak AM transmitter

I've made this simple AM transmitter: http://makerf.com/posts/fun_with_crystal_oscillators_part_3 The author of this circuit, claims that would be possible to extend the range of this transmitter ...
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1answer
60 views

Digital signal over AM radio [closed]

I am trying to send a digital signal over radio and I am having trouble modulating the input to the radio circuit. I am a complete beginner so I am doing this only as a learning exercise. I have the ...
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0answers
41 views

Radio direction finding methods

I am a little bit confused about the different Radio Direction Finding methods and I want to chose the simplest method for what I want to do: find azimuth and elevation angle of arrival of my ...
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0answers
36 views

Weather Balloon Wireless Mesh Networking

I am trying to get real-time data feed from a homemade weather balloon radiosonde with the objective of sending HD video during the flight; this could be relevant for GoPro-ers who want to send their ...
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1answer
77 views

Is it possible to power an LCD by radio wave?

We've all heard of crystal radios that essentially draw their power from the radio waves which induces a tiny current in order to generate the sound we hear from them. There are companies that are ...
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0answers
44 views

Colpitts vs. Hartley?

What are the pros and cons of using a Colpitts or a Hartley configuration for an oscillator?I know that the difference between them is the form of feedback, but does one or the other perform better ...
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0answers
51 views

Superheterodyne receiver with voltage controlled oscillator

I'm new in electronics and I want to create a FM receiver that performs a product of the received RF signal and a local signal (the local signal is also frequency modulated with a Voltage Controlled ...
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3answers
342 views

Radio wave interference

While studying radio electronics I stumbled across a small article about wave interference on the same frequency. The article was very simple explaining that if there a stronger emitter on the ...
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2answers
44 views

How dBuV value changes with distance?

I've got an emissions source that's designed to generate a peak at a certain frequency that when measured by an antenna 3m away gives a value of X dBuV. If the emissions source if moved closer to ...
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2answers
56 views

what is the maximum range of citizens band radio computation

i have been computing the maximum distance for a citizen's band radio. i don't know if my computation is correct because the answer is so large, appx. 280000km. what do you think is wrong with my ...
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1answer
75 views

channel seperated communication in RF

In RF communication the carriers such as 950MHz, 133MHz are available under 1 GHz. If there are 50 devices using the for example 433MHz carrier, then how could large number of devices talk to each ...
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0answers
40 views

Several RF transmitter and receiver circuits work without interference

I need help or giving me any approach to make transmitter/receiver circuits which they will be in the same range, but every pair (Tx, Rx) works on a precision frequency spacing without any ...
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1answer
71 views

Should I use a passive or an active filter?

simulate this circuit – Schematic created using CircuitLab I need to design an am receiver as a project. On the front end I have three modules; BPF1 the "roofing filter" or the ...
3
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2answers
152 views

What RF attentuator would be used for the HackRF?

Background info: The HackRF is an SDR Radio capable of receiving and transmitting frequencies from 10MHz to 6GHz. Michael Mossmann, the creator of the HackRF, states in his wiki that: The ...
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0answers
47 views

Connect CB Microphone to Smartphone

I'm planning to use an Android smartphone as a realtime voice effects processor with my CB radio. I did a little internet research about the way Android devices detect a connected headset and found ...
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2answers
119 views

I can not receive radio waves using LM386?

I've made two different circuits to receive RF using LM386 but they doesn't work. I've changed the values of C2 and L1 to change the frequency. I've also changed the gain but nothing happens. The ...
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0answers
81 views

Is it possible to make a device that will transmit a sound\suppress my neighbour speakers?

Let's say, I've a highly inadequate, impudent neighbor who is listening to music very loudly. I've seen on the Internet that's there's a possibility to transmit your own audio to a neighbor speakers ...
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3answers
483 views

Is it possible to exchange information between arduino and android phones easily using nrf24l01? [duplicate]

I need to send information from arduino to an android phone, having some app actively listening for radio communication from arduino. Using nrf24l01 is that possible? The best scenario would be ...
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2answers
2k views

Why aren't ferrite rod antennas used in WiFi?

Does it have something to do with soft ferrite's low coercivity, still not low enough at gigahertz frequencies? See, I'm putting together high gain receiver antennas and transmitter antennas. Space ...
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1answer
99 views

RF - separate transmitter and receiver antennas for half duplex

i was wondering why is it for just half duplex systems, don't we have a dedicated transceiver and a dedicated transmitter antenna. ok, just hear me out... assuming we are using grounded monopoles, ...
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2answers
89 views

How can the 2.4GHz ISM band have 130+ channels?

I am a relative beginner regarding wireless communications protocols and I am looking into the protocols used by toy helicopters, in particular the Hubsan X4. According to more experienced people who ...
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1answer
46 views

What is a channel tap?

In wireless communication, I am confused about what people are referring to when they use the term 'channel tap.' Can someone explain the term or provide me a definition? Any help will be ...
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1answer
62 views

How to listen to radio communications from a transmitter?

I have two devices communicating at a frequency which I don't know. I want to listen to that communication so that I can replicate one of the devices and fool the other. Basically I want to reverse ...
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3answers
118 views

Can you use your computer to make a radio transmitter? [closed]

I was wondering, is it possible to oscillate the electronic signal emitted from the audio jack on a computer ? Because I would like to somehow create a simple radio transmitter just using my computer. ...
0
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3answers
205 views

How to build a simple LED transmitter and receiver

I'd like the distance to be about 1/10th of a mile; less distance will be fine if that's easier to build. What tools and parts may I need for this? I have plenty of LEDs lying around and I have ...
3
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2answers
302 views

Car radio output voltage

I am working on an amplifier for a car radio for a friend of mine. He is away for few weeks so I can't measure the radio output. That's why I am asking here, does anyone know, what's the ...
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1answer
322 views

How to build an FM transmitter and how does it work?

I have become interested in radio transmission and would like to know how to build an FM radio transmitter. When I search for information I either get a block diagram or a video of someone putting it ...
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12answers
3k views

Do we know what a radio wave looks like?

In precalculus class we are learning about sin/cos/tan/cot/sec/csc and their amplitude, periods and phases shifts. I've studied electronics on and off for about a year. I would like to know if we ...
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1answer
65 views

Designing radios with gnuradio

I am looking at FM radio receiver designs others have created with gnuradio. There are a couple of signals questions I have after looking at these designs. The source (e.g. rtl-sdr) samples at a ...
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1answer
44 views

How to detect several agents within a radius, what is the best and easiest way to do it?

I have a room with 30 objects which may or not be present, and I want to be able to detect which objects are in the room. My first idea was to attach a RFID tag to each one of these objects and have ...
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2answers
53 views

Which characteristics of a Radio signal are involved to be selected by radio receiver? [duplicate]

the radio antennas receives millions of signals. how our radio selects the appropriate signal as it's input? which characteristics of the signal are involved for this selection.
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2answers
49 views

Shared antenna on multiple 2.4Ghz receivers

I want to use several 2.4 Ghz transcievers (not sure which IC yet, either Atmel AT86RF*** or TI CC) in order to build a simultaneous multi-channel sniffer. The transciever output is differential. I am ...
0
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1answer
34 views

Using RF for relative direction finding for short ranges (sub 10m)

I'm considering building a short-distance direction finder to determine the relative position of two objects. I want to be able to determine direction through other objects, which eliminates IR or ...
0
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1answer
47 views

Best RF frequency for my application

I need to design a device that can transmit an RF signal about 200 meters. The data transferred is very simple. One device simply has a button, that when pressed transmits a two-digit ID to the ...
2
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2answers
86 views

Data Whitening Block Diagram

I would like to understand this block diagram and how it relates to the formula: g(D) = D^7 + D^4 + 1 Supposedly this helps to generate a whitening word used within bluetooth radio, the empty boxes ...
3
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4answers
470 views

Does this simple RF transmitter circuit actually work?

I've come across this circuit a few times while searching for simple transmitter circuits, and decided to try it. According to this site, it should be transmitting at around 90Mhz. ...
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1answer
104 views

How much RF-interference does a typical desktop computer produce? How much does a metal case without windows reduce it?

It's fairly common now to see desktop computers in cases with large windows cut in the sides. I've always been under the impression that if unshielded, computer equipment will produce a lot of radio ...
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1answer
405 views

What is the best and simple circuit diagram for a radio receiver to receive radio waves in Citizen's Band [closed]

I am building a two way radio system using the citizen's band in India. The transmitter is using a 555 timer IC clocked at a frequency between 26.957-27.383MHz to transmit AM waves. Can you please ...
1
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1answer
121 views

Making my own radio transmitter

So I have recently been interested in Radio electronics, and I have been looking around to buy a HAM radio transmitter,but they tend to be very expensive (and you learn nothing by just buying it). So ...
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2answers
128 views

Is possible to build -168 dBm amplifer?

we know that GPS receiver can reach sensitivty of -168dBm, and also it is possible to make receivers with similar sensetitvity can operate at another bands/frequencies . but I just want to know if ...
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1answer
67 views

What Heinrich Hertz did different than Faraday

Now this wiki page says Heinrich Hertz is the person who found radio waves. And here, it describes how the experiment has done. He basically made first antenna. But years ago, Faraday found law of ...
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2answers
124 views

Filter for radio receivers

I am in need of an intermediate frequency (IF filter) for somewhere around 200 Khz as intermediate frequency. However, I know just the bare minimum of filter design ( learnt all that a couple of days ...
1
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4answers
289 views

High precision trilateration in a small space and without ultrasound

I need my robot to be able to find its position in a room with ±10cm accuracy. For that I have decided to place two radios right at where the door is and the third radio on the robot. The room is ...
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1answer
93 views

Radio signals blocked by red bricks / aluminum insulation

Do red bricks home/building and aluminum insulation diminish the strength of radio signals?