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Czech RF10 Battery Help [on hold]

Need some help. I purchased a Czech RF-10 radio which has a battery box with Five Ni-MH "D" cells inside.. (see prc68.com) I would like to know how to recharge these batteries. Can I use a universal ...
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1answer
48 views

Weather radio antenna [on hold]

I am trying to build a simple weather band receiver. I bought a breakout board and im trying to find an antenna. I ripped apart a weather radio that looked to have a (rubber ducky antenna) and found ...
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3answers
45 views

Tuning a radio wave receiver

Variable capacitors are used in tuning many circuits of radios. I read the theory of basic tuning and resonance frequency. What I understand by changing the capacitor we change the resonance frequency ...
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1answer
47 views

Streaming UHF/VHF/AM/FM over IP

I am working on a project that can stream TV and Radio signals over IP. I found a device to capture the signals and send them over IP realtek-rtl2832u but I am ...
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2answers
75 views

When powering a Nrf24L01 hooked up to an arduino by external battery does ground still go to the Arduino ground?

So as mentioned in this article, the radio chip might have power problems and an external power source is recommended: http://arduino-info.wikispaces.com/Nrf24L01-2.4GHz-HowTo My question is for the ...
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1answer
61 views

How to measure distance using radio waves? [closed]

Have you seen http://www.youtube.com/watch?v=CvZ4_SIAxDY I need a similar circuit to do the same. There are two module. Module A and B. A sends to B and B returns signal to A. How to find the time ...
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2answers
117 views

How small can a radio transmitter be?

Lately, I've heard about a fascinating new technology called DNA Origami, where incredibly tiny machines are folded out of DNA. Using CAD software they are able to build all sorts of interesting ...
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0answers
58 views

Reason for choosing particular frequencies for ISM bands

There is a number of ISM bands, including the widely used 2.4 GHz. But which were the reasons for the FCC and ITU to pick those bands? I suppose, that with 2.4 GHz there's a connection with water ...
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1answer
82 views

How does a cube sat communicate with ground station with a 1w antenna

I heard that cubesat signals can be received with a hand held radio. Its confusing me that how a 1 metre antenna radiating 1watt energy can simply be received using hand held radios. I am designing a ...
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3answers
217 views

Full duplex shared frequency radio?

Normally shared frequency analogue1 radios (CB, aviation, etc.) can't receive when transmitting, because the signal being transmitted is much louder and will jam any signal from different transmitter. ...
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1answer
51 views

Radio Transceiver bulkhead connection and Ground

I have a problem regarding mounting of RF transceiver. The main board inside metal cabinet is floating and when I check the antenna SMA bulk connector its outer case has a connection to circuit ...
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1answer
80 views

Making an AM radio with a silicon diode

I've been working a few days on this and have still come up with nothing. I am trying to make an AM radio using a silicon diode, but all of my attempts have failed. I believe my latest attempt most ...
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41 views

No radio signals with antenna

I have an antenna I made with about 2 feet of insulated copper wire, stripped at one end. The antenna is connected to the positive side of a 1000uF capacitor, using this circuit. I am using a 741 ...
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1answer
88 views

How is signal strength calculated?

How is the signal strength calculated in case of cell phones ? How will the signal strength be calculated in case of WiFi networks ? I am not certain if the question I am asking is the same as QoS ...
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1answer
235 views

Why does the 802.11 wifi spec allow for 11 channels?

The general wisdom is that it is better to only ever use channels 1, 6, and 11 as they are the only three non-overlapping channels for 2.4ghz wifi (in the US), and two adjacent networks on the same ...
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1answer
28 views

Know the transmission speed between PICAXEs with Radio module

I was wondering if I could know the transmission speed between 2 PICAXEs using an Radio Module. At the moment I tried to send data between 2 PICAXE 40x2 only with the 433MHz Radio Transmitter. The ...
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1answer
64 views

Radios and Power [closed]

RF newbie here. Lately I've been experimenting with RF. I built some simple oscillators, managing to get a tank circuit working as well as buffering the 1 megahertz output of a tin can oscillator. ...
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1answer
164 views

Radio Transmitter using Crystal Oscilliator

I am on the mission to control my RC car using arduino. The simplest way I thought of doing this is to add arduino outputs into the transmitter. Long story short I wanted to learn more about how these ...
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0answers
39 views

sending data with cc2510

Hy, I'm trying to send simple 1 Byte package with cc2510dk-mini. The idea is to press button on on device and the led on the other lights up. I'm stuck with the problem, when I try to send data, radio ...
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2answers
200 views

NRF24L01+ Power Amplifier -dBm options to milliWatt

From the datasheet for these module I have the folowing power settings available (listed form highest to lowest), I need to know what they equate to in milliwatt, as in Australia maximum 2.4ghz ...
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1answer
159 views

Properties of a WWVB Receiver

In this article the author dissects a radio-controlled clock that syncs with the NIST transmitter, WWVB, in Colorado. The radio receiver seems to be a single integrated unit: Of special note is ...
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1answer
164 views

Smoothing and decoupling power source input

I am transforming an old battery-only radio so I can connect it through a DC input. I found an earlier model diagram that includes the DC input (picture attached). I have connected a 18 V DC source ...
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3answers
83 views

What's the best shape and material for my Wi-Fi range booster dish?

I want my wireless LAN to be available in an apartment that is 459 feet (140 m) across. I'm thinking about putting a router (bridge) that has an omnidirectional antenna on the roof of my apartment, ...
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2answers
115 views

Intercept SPI of RC helicopter controller

I've got this radio communication with an RC helicopter. I found that the RX on the heli is using an AVR MCU and a CYRF6989 2.4Ghz chip to communicate with the controller of the heli and translates it ...
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1answer
111 views

Loudspeaker transducer FCC certification?

Is FCC certification necessary for speaker transducers that are sold as assembled units in their housings? I found information on active speakers needing fcc certification, but what about passive ...
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1answer
175 views

How do “Wire Wound Chip Inductors” work [closed]

I have a police scanner that has a couple of modules in it. One of these modules is marked 390G (Data Sheet) I can't see the other modules number but it looks identical. I know they are NOT the ...
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2answers
85 views

How to show field strength varies as 1/r

This is a question, from a radio amateur, that should have a straightforward answer: but I cannot find one on the Web. Is there a robust but simple explanation, not needing advanced maths, as to why ...
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1answer
176 views

How can this FM transmitter modulate?

simulate this circuit – Schematic created using CircuitLab This is a minimalist FM transmitter I've found from http://www.talkingelectronics.com/projects/Spy%20Circuits/SpyCircuits-1.html ...
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1answer
66 views

How does pseudo-random noise increase DCF77 accuracy

A few years ago the Germans added a pseudo-random noise signal (from a LFSR) to their time reference DCF77. I heard this should allow you to get a more accurate signal at the receiver side. But the ...
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1answer
54 views

Screen of a mobile phone inside something [closed]

As an image for a speech I want to be able to shield of the coverage of a mobile phone. I thought of putting it in something. So I grabbed the stewing pan made of cast iron from the kitchen. ...
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1answer
107 views

What RF protocol do wireless mouses and keyboards use to communicate?

I'm designing a device which uses Bluetooth 4.0 (Low Energy) and I noticed how hard it is to achieve decent battery life, but the average mouse or keyboard lasts months/years on two AA batteries. I ...
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2answers
114 views

How is mobile communication(between pilot and ATC ) made possible from airplanes?

I have heard that communication using mobile phones begins to degrade when used on a vehicle moving at speeds above 200 km/hr due to doppler effect as described here (p-22). How is this limitation ...
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3answers
611 views

How does RF anti-jam technology work?

I'm pretty certain that RF jammers work by overpowering the target signal with their own higher powered signal at the same frequency. So the question is, how does anti-jammer technology negate the ...
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1answer
121 views

BLE Scan interval and window

With Bluetooth Low Energy, you specify a scan window (how long to scan) and interval (how long to wait between scans). Would there be any difference between scanning for 10 ms every 100 ms, or ...
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2answers
506 views

How does Frequency Modulation work with radio frequencies?

Inspired by this question: What is the basic difference between AM and FM radio? I got to wondering: If I put my FM radio on some radio channel (Let's just say 100 MHz to pick some number), ...
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3answers
218 views

Regarding Radio Frequency (RF) when a Receiver/Antenna Setup can receive DC - What Exactly Does that (DC) Mean?

I do not have a strong foundation in RF. I have been doing some research but I still do not properly grasp what it means if a receiver/antenna can do DC to X Hz. For example this Funcube Upconverter, ...
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1answer
93 views

Using Titanium as antenna in implantable tracking system

I have some question regarding using titanium as antenna. I have to think about an implantable tracking system for animals. One of the requirements is that it should be as small as possible. Other ...
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2answers
341 views

Why do some radio antennas require a path to ground and some do not?

I'm currently learning the basics of radio and have noticed that some radios, such as crystal radios, have a monopole antenna that is essentially a wire buried in the ground. However, other radios, ...
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2answers
100 views

Is there a “canonical work” for radio amateurism?

My friends and family have been radio amateurs and I'm not very familiar with radio technology. I know basic mathematical physics but I only know the X25 and the As400 (or what's its name) by name and ...
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0answers
93 views

uart to phone jack

Setting aside permission issues and looking at the technical means to achieve it, I wonder if anyone could comment on connecting a UART line to the mic input of a FRS radio. Unlike phones, the input ...
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2answers
135 views

What Modulation does weather radio use?

Here is the official site which says the frequency which weather radio broadcasts at (around 162 Mhz). The site doesn't say anything about modulation though. What modulation is used in this radio ...
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3answers
201 views

Why is receiver RSSI so much lower than the output power of a transmitter?

When we measure the output power of a small transmitter we might see something around 30 dBm (1W) but a receiver/WLAN card/UE ...
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4answers
998 views

AM Modulator Mixer Circuit

I found a very basic AM transmitter circuit on the youtube video here. The schematic is below: I'm a bit confused on the op-amp circuit on the right. It seems that the op-amp is really only ...
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3answers
339 views

Why would I use a transformer instead of one inductor in a crystal set?

I'm reading up on A Simple Radio Receiver. I have a question about this image: The signal from the antenna (perhaps a few tens of microvolts, or hundreds for a nearby transmitting station) ...
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3answers
377 views

relationship between frequency and signal strength

I know that [the commercial broadcast] radio spectrum is divided into several chunks and each chunk is assigned to be used by different radio stations. Suppose that radio station S1 is using 93MHz and ...
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0answers
59 views

is it possible for other radio chips to communicate with an xbee?

Do xbees only communicate with each other or is it possible for other radio chips to communicate with an xbee too? If so, what radio chips specifically? I would appreciate if there code samples ...
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3answers
160 views

Why is speech malformed when listening to a USB signal with an LSB receiver?

When you listen to an LSB (Lower Side Band) signal with your radio set to USB (Upper Side Band) or vice versa, the speech you hear is malformed. What causes this behaviour?
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2answers
138 views

Two signals alternately on the left and right of a frequency

I was listening to the WebSDR of Twente University, just outside the amateur band, and saw these signals. The x axis is frequency in kilohertz, the y axis is time, where the whole axis shown is about ...
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2answers
184 views

What is the bandwidth of an antenna ? and what happens when a narrow bandwidth is used?

I'm trying to understand the bandwidth of an antenna in order to choose the right one for my next project which involves a Nordic 2.4GHz radio transceiver (NRF24 series) that operates from 2400MHz to ...
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1answer
142 views

How do receivers know what to output to radio speaker or TV screen?

I understand that receivers are often used with mixers which take the sum and difference of two signals to make an output signal. How does a radio signal of say 102.5 MHz know to tell the speakers to ...