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66 views

Old Radio RF Transformmers

I want to make a TV transmitter (http://electronics-diy.com/electronic_schematic.php?id=851). There is an RF transformer on it (T1:4.5MHz 1F-can-style RF transformer) that I want to find it from old ...
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4answers
967 views

Why do characteristic impedances matter only when traces are longer than half a wavelength?

Why are characteristic impedances of traces not considered when the traces are shorter than half a wavelength? I've had the same issue with light diffraction, which happens when pinholes are smaller ...
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1answer
29 views

Merging right & left signals to mono with aop?

Sorry for my english i'm a young french. I want to design an audio transmitter to connect my pc to my Hi-Fi without Jack cables. For now i just want to send a mono signal because sending a stereo ...
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1answer
39 views

Send action signal via radio using energy generated by piezo

I have an idea going on in my mind but I am not sure if it is even feasible, so please be patient! Here is my problem. I have a set of chairs, say several dozens. I would like to be able to monitor ...
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1answer
30 views

Two 2.4GHz radio modules (XBee+Bluetooth) on same PCB. How to minimize interference?

I'm designing a PCB with XBee radio module and a bluetooth module (RFDuino SMD with XBee 2mW Radio). Since both of these modules are using 2.4GHz, are there any special consideration about how to ...
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1answer
39 views

Help Identifying Radio Component and Replacement Part

My girlfriend picked up an old Philco tabletop AM radio. If I had to guess, I'd say it was manufactured around 1960. I couldn't find any model number or year stamp. It's encased in plastic. It powered ...
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0answers
37 views

Using a radio board with Contiki-OS on lpc1347 mcu

I am trying to build a port for Contiki on my lpc1347 board. So far I have been able to run a basic LED blinking/Hello_World Contiki process/program on my board. My next goal is to use a cc2530 radio ...
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3answers
112 views

What are the basics I need to know to power LEDs with RF at a range of 30 feet?

I would like to light up a path in the woods with hundreds of LEDs using RF. The idea is that I would carry a RF transmitter powerful enough to light LEDs. As I approach the LEDs would get brighter, ...
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0answers
35 views

sub-1Ghz radio compatibility

I want to ask something about the compatibility issue of the sub-1Ghz radio. There are many readily available sub-1Ghz radio now. If I am using two different RF chips (such as TI's cc1120 and Silicon ...
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0answers
42 views

AM radio design reference

I'm trying to design a lab exercise for university students that centers around the design and build of an AM radio. I've found a ton of radio plans on the internet, but most of them just tell me ...
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0answers
23 views

Transmit distance (Frequency)? [duplicate]

How frequency affects the signal transmit distance? Is there any equations that describes this? I know that input power is important factor, but what about frequency?
6
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1answer
553 views

Why are the capacitors set up this way in this old tube radio?

I'm trying to figure out what's going on with these capacitors, so I can replace them in an old tube radio, but why are they connected in this way? simulate this circuit – Schematic ...
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4answers
836 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 ...
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0answers
69 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
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1answer
60 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 ...
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2answers
88 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 ...
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1answer
35 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 ...
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1answer
81 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 ...
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2answers
64 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 ...
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1answer
155 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 ...
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3answers
86 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 ...
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1answer
64 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
128 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
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 ...
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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 ...
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1answer
94 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
122 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
72 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
66 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
70 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
86 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
58 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
69 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
356 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
53 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
80 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
93 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
60 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
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1answer
94 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
422 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
97 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
206 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
103 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
851 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
152 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
123 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
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1answer
134 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
69 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
156 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. ...