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27
votes
8answers
3k views

Can a radio transmitter somehow detect the number of receivers in its area?

During conversation, a colleague proposed that over-the-air television and radio broadcasters can determine the number of viewers or listeners based on the "load" on their signal. This seems to me ...
-4
votes
0answers
59 views

How do I make a antenna more sensitive to radio waves [on hold]

What components do I need to make a antenna more sensitive to radio waves I'm working with 2.4GHz but I don't want to extend my antenna. I'm trying to make it more sensitive to radio waves. Do I ...
-1
votes
0answers
60 views

Basic circuit drawing [on hold]

I was wondering if anyone knows of a simple circuit drawing. I want a produce a 2.4ghz electromagnetic wave that can travel 50 metres. It's not going to transfer information. So it dosnt need to be a ...
1
vote
0answers
41 views

How to choosing the right transistors for active antennas

I'm trying to build a Mini Whip active antenna that receives 10KHz to 20MHz. But I'm having trouble finding the right components especially the transistors. It calls for a J310 and a 2N5109, which ...
0
votes
0answers
40 views

433MHz transmitter and receiver pair doesnt work [migrated]

I have a pair of 433 MHz transmitter and receiver: Transmitter is connected to Arduino pro mino, receiver to Arduino uno r3. Output of receiver on serial looks like that(it doest change much): ...
3
votes
0answers
41 views

Arduino+2X12 LCD to emulate a defective Kenwood HF rig display unit

I have an HF rig with a bad display init (LC7582A driver and custom LCD with 9 seven-segment numeric indicators and some icons making for a total of a 100 or so segments). The input pins of the LCD ...
0
votes
2answers
68 views

RF Transmit Power in an ISM band

I was browsing through some OFCOM Frequency Allocation Tables for use on a small project I'm doing. I require the use of some unlicensed ISM bands in the UK, and found that the lowest unlicensed band ...
2
votes
3answers
187 views

Transmit power vs. Transmission power, is there a difference?

I was reading a scientific paper, and the authors sometimes use the term "transmit power" and sometimes "transmission power". Is there a difference in terms of correct English usage? Examples: ...
1
vote
3answers
75 views

Shortening the coax on UHF CB antenna caused SWR to get worse, why?

I shortened the coax cable on my car's 477MHz CB antenna because the braid was frayed at the transciever connector end, and a metre or so of spare coax was coiled up behind the dash. I thought if I ...
11
votes
4answers
3k views

If an FM signal has different frequencies, how does the radio receive the signal in a fixed frequency?

If an FM signal has different frequencies according to the modulation, how does the radio receive the signal in a fixed frequency like 103.2 MHz?
1
vote
2answers
74 views

Trouble tuning am radio

I have been following the tutorial below to build an AM radio, and when powered on I was picking up what id presume to be radio waves (what I'd describe as a mishmash of "whooshing" sporadic ...
0
votes
1answer
53 views

Create a new wireless protocol for industrial

I'm working on project that lets industrial machines communicate to each other wirelessly. It seems that Zigbee at 868MHz is the best choice (if you have any other suggestion it would be great), ...
0
votes
0answers
49 views

Reason for radio device functioning only when connected with cables between connectors

I have a prototyped board with a 2x4 female connector which is supposed to connect to a NRF24L01+. If I plug it in directly it's not working, however if I connect cables between them everything is ...
-7
votes
2answers
72 views

Can we send text data over FM radio? [closed]

Can we able to broadcast text data over the FM radio.If yes, how can I implement this.
1
vote
0answers
58 views

Radio Electronics

I'm a beginner in radio electronics. I have basic experience building circuits with both passive and active components. I was wondering if it was at all possible to build your own transmitter, ...
3
votes
1answer
154 views

What is this type of radio fm antenna connector called?

I'm looking for an antenna replacement for my dad's busted radio (iHome IH8) and I'm having some trouble finding the name of this type of plug. The only things I find when searching online are coaxial ...
0
votes
1answer
85 views

Old Radio RF Transformmers [closed]

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 ...
19
votes
4answers
1k 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 ...
1
vote
1answer
51 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 ...
1
vote
1answer
50 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 ...
0
votes
1answer
51 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 ...
1
vote
1answer
43 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 ...
1
vote
0answers
41 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 ...
2
votes
3answers
124 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, ...
0
votes
0answers
39 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 ...
0
votes
0answers
46 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 ...
0
votes
0answers
24 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
votes
1answer
568 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 ...
5
votes
4answers
1k 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
102 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
73 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
112 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
36 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 ...
3
votes
1answer
84 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
votes
2answers
67 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
206 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 ...
1
vote
3answers
90 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
66 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
140 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
votes
0answers
21 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
53 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
137 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
176 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 ...
2
votes
0answers
74 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
88 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
104 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
85 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
362 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
58 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
85 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 ...