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2
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1answer
176 views

Can anyone explain this capacitor setup? “repairing old tube radio”

I'm trying to figure out whats going on with these capacitors so i can replace them in a old tube radio but I don't understand why there connected in this way. simulate this circuit – ...
0
votes
0answers
24 views

Is it possible to use the DASH7 protocol in an arduino? [migrated]

I've been reading about the protocol DASH7 but can't find much documentation about it. There seems to be a protocol stack called OpenTag writen in C and I want to know if there is something familiar ...
5
votes
3answers
749 views

How does an AM radio filter out only the desired frequency?

I understand that electromagnetic waves in the air induce an alternating current in the antenna. I also understand how, once you filter the signal to obtain the desired frequency, you can get the ...
1
vote
0answers
39 views

IF transformer color codes

Is there any standard color code available for IF transformers? Generally in most of the Japanese radio receivers I see red color slug for MW oscillator, white and yellow slugs in AM IF stage, ...
0
votes
1answer
52 views

Alternative to AM and FM transmitting for data transmission?

So, I need to communicate wirelessly between a micro-controller and my computer. I'm building a radio receiver circuit, and a radio transmitter circuit that works on FM transmission. However, I had an ...
0
votes
2answers
70 views

Arduino along with radio tx/rx

I'm thinking about a project similar to the home-automation systems etc... Few problems came in the way, The cost of the Arduino radio receivers/transmitters is huge, especially if I need few of ...
0
votes
1answer
29 views

Delayed Overcurrent Protection

I trying to find a solution for a problem that I have with a system I am responsible for. The system runs on radio control, the problem we had is one of the radios got stuck on transmit and blocked up ...
4
votes
1answer
80 views

How to ensure a RF module is indeed FCC compliant as advertised?

Suppose a buyer buys RF modules from China and wants to ascertain that they're indeed FCC compliant as advertised. I'm guessing that this should be a fairly common issue since Chinese ...
0
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2answers
61 views

Could the metal shield on radio modules be tampered with?

I see that most radio modules have a metal shield. Is it for keeping the radio waves inside? If so, could a shield be too thick for its purpose? For instance, if one solders another piece of metal ...
3
votes
1answer
112 views

Must FCC-certified modules be labelled with the correct FCC ID?

The manufacturer of this radio module I bought claims that it's FCC certified, but there's no FCC ID on it (though there is the FCC logo). If the final product is to be FCC tested, would it then be ...
0
votes
2answers
69 views

Dipoles lengths underwater vs on land

A submarine (for example) uses a VLF communications system to remain in contact with its headquarters while submerged. The submarine drags a resonant dipole wire antenna behind it in the water. The ...
0
votes
1answer
63 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 ...
2
votes
2answers
114 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 ...
0
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0answers
20 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 ...
0
votes
2answers
48 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 ...
0
votes
1answer
76 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 ...
1
vote
1answer
98 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 ...
0
votes
1answer
67 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 ...
0
votes
0answers
53 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 ...
2
votes
0answers
62 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 ...
1
vote
1answer
79 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 ...
0
votes
0answers
50 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 ...
1
vote
0answers
62 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 ...
3
votes
3answers
353 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 ...
0
votes
2answers
50 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 ...
0
votes
2answers
77 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 ...
0
votes
1answer
88 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 ...
0
votes
0answers
53 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 ...
0
votes
1answer
84 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
votes
2answers
302 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 ...
0
votes
0answers
73 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 ...
0
votes
2answers
168 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 ...
0
votes
0answers
89 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 ...
-1
votes
3answers
719 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 ...
7
votes
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 ...
-1
votes
1answer
131 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, ...
0
votes
2answers
106 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 ...
0
votes
1answer
75 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 ...
0
votes
1answer
65 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 ...
0
votes
3answers
140 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
votes
3answers
281 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
votes
2answers
477 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 ...
1
vote
1answer
679 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 ...
16
votes
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 ...
1
vote
1answer
77 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 ...
1
vote
1answer
50 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 ...
0
votes
2answers
57 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.
1
vote
2answers
56 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
votes
1answer
35 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
votes
3answers
86 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 ...