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How to troubleshoot VHF radio transmits but does not receive

I have a marine VHF radio on a sailboat. There is a coaxial antenna leading up the mast (roughly 40 ft in height). It has had a recent issue with receiving transmissions, however it appears to ...
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0answers
33 views

WiFi obscuring 433mhz signal reception

I have a WiFi arduino device with a 5dbi omnidirectional antenna and a 433 mhz receiver board, based on Aurel AC-RX with a 17cm stranded copper wire Antenna both enclosed into the same box. This ...
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0answers
44 views

Can anyone please explain the working of a radio transmitter

I found this circuit online: I found explanation on how a radio transmitter works in this site: http://www.dummies.com/how-to/content/radio-electronics-transmitters-and-receivers.html However, I am ...
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2answers
90 views

Why would phones have a radio receiver, but not activate it? [closed]

According to some recent news articles, many cell phones including iPhones and Androids have built in FM receivers, but they are not "activated". Why would the phones have such a feature but not ...
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1answer
102 views

Old radio amplifier circuit explanation

could somebody explain me how does this audio amplifier circuit from old radio is working ? I understand role of last transistors 413,417 and 415,419 but what is the point of T409 and T411 and other ...
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2answers
20 views

Xbee XB24-ACI range without antenna

Anybody have experience with the range of these xbee modules? I reading about 10 kilometers: http://diydrones.com/profiles/blogs/what-is-the-maximum-range-of-an-xbee-lets-find-out But according to ...
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3answers
80 views

Electromagnetic Radiation and Communication! [closed]

I read that the accelerated charges create electromagnetic field/spectrum which consists of following different waves: gamma X-rays ultraviolet visible light infrared microwaves radio waves ...
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0answers
43 views

Arduino 433MHZ transmit + receive on the same board

I have an arduino nano with the popular cheap 433Mhz receiver + transmitter on 2 different pins: http://www.instructables.com/id/RF-315433-MHz-Transmitter-receiver-Module-and-Ardu/ I would like to ...
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1answer
51 views

How to get current from radio signal circuit

I followed this circuit http://www.saers.com/recorder/craig/TENewsV2/TENews68/RadioWaveEnergy.jpg to harness radiowave and turn it into dc and it seems to generate around 1.4 volts but interestingly ...
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2answers
56 views

Dispersal of radio energy as it moves further away from the source

I apologise for the wording of my question, it will no doubt come across as confusing. If there is anything you are unsure about please feel free to ask me. Question As a radio wave moves further ...
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1answer
84 views

Maximum range of 27 MHz ISM band NLOS radio broadcast

What is the maximum range of a 27 MHz ISM band when transmitting at full power? I am interested in general situation for US and EU but that will go back to the power limits allowed. My country (CZ in ...
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1answer
38 views

Can I connect an amplifier to a Crystal Radio?

I am wanting to create a crystal radio that connects to my amplifier (It is for a guitar and has 3.5mm and 1/4" jacks). The diagram is as shown: Would this be possible and work? If not, please ...
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2answers
44 views

I'm confused about how to calculate noise for an SNR? [closed]

My Rx radio is getting -60 dBm but I don't know how to find the noise. My thermal noise is on the order of E-12 so it barely affects my SNR. Where does noise come from and how can I calculate it?
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2answers
581 views

The classic 1N34A Ge Diode has a Vf of 1V… how could a diode with such a high Vf work in crystal sets they were packaged in?

Back when I was younger I got a crystal radio set kit which included a 1N34A Ge diode (as far as I can remember, I don't have it anymore). I wanted to build one again recently and all I had a was a ...
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1answer
176 views

How to make radio transmitter and reciver [closed]

I want to make a simple but useful radio transmitter and reciver.I dont know which one is better, Fm or Am or other types? Just want it to send pulses like morse code not complicated voice or other ...
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1answer
423 views

Why FM stereo uses DSB-SC instead of VSB?

Using vestigial sideband instead of double sideband supressed carrier could make the baseband stereo signal more compact. Would there be any other benefits or downsides of employing VSB?
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2answers
104 views

Antenna for broadcast AM reception on ARM Radio SDR

I'm trying to build the ARM Radio project detailed here. I routed and fabricated a PCB for the anti-alias filter and preamplifier shown on page 2 of the linked PDF, and reproduced here: ...
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1answer
94 views

Effect of Small and Large Signal Transconductance on the Colpitts Oscillator

I've been following Ron Quan's book: Build Your Own Transistor Radios and I've come to the section where Ron is analyzing the oscillator circuits used in his designs. In particular, he discusses the ...
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1answer
138 views

How does this oscillator work?

I am trying to understand the following oscillator from a Cyclone 40 transceiver (http://www.4sqrp.com/cyclone.php). Here the the VFO (in the actual device, the inductor has a bolt through it to tune ...
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2answers
182 views

What are the units in which a radio signal's strength is measured?

I'm kind of confused about which is the most correct unit when it comes to the measure of wireless signal's strength. It seems that the correct unit is V/m (usually expessed in dBuV/m), however it ...
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1answer
103 views

Tuning simplest FM to 93.5MHz

FM Crystal Radio L - 4 turns #18 copper or silver wire, 12mm inside diameter, tapped at 2.5 turns Ant - 7 inches of #18 bare copper wire C1 - 18 pF ceramic capacitor C2 - 50 pF air variable ...
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3answers
158 views

Plausable deniablity / steganography in radio transmission

Normally in a wartime scenario etc. strict radio silence is observed to prevent the enemy from evesdropping on your transmissions. Encryption solves a part of the problem. Now the enemy cannot ...
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2answers
95 views

What RF antenna connector is this?

Funny question, but what type of RF connector is this? I think it might be SMA, but I might be wrong. After fiddling with the autofocus forever: (In case the image doesn't load; here are the ...
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1answer
387 views

simplest FM radio receiver?

As per this building simple radio it is the simplest AM radio receiver. obviously this is very poor AM receiver.(but it was working for someone in comment) I'm wondering what will happen when ...
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2answers
71 views

Pickup Signal from a Wire - without a physical connection

I am not an RF engineer and I don't even know if what I'm asking is possible. The idea is that the system will be outputting a 12V 10KHz signal onto the wire with one end connected (Wire Under Test) ...
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1answer
148 views

Would you explain the output waveform of this FM transmitter circuit?

I build this circuit and it works. I wanted to look at the output waveform by my soundcard oscilloscope software. I would expect something like the following picture: But the output waveform was ...
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2answers
187 views

Building an fm transmitter broadcasting simultaneously to all fm frequencies

I would like to build an FM transmitter that transmits a signal to all fm frequencies simultaneously, so that any nearby radio tuned to any frequency can receive this signal. Is it possible to do this ...
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1answer
159 views

How can a diode act as a detector in a crystal receiver?

I was reading about old crystal radios and read that in a crystal receiver the radio signal in the air is first selected by a tuning coil and then converted to audio signal by a diode. I am confused ...
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2answers
94 views

Why are there more than one RF amplifier in a TRF receiver?

In literature TRF receivers are said to be hard to tune because they have many RF amplifier stages in reception. They all need to be tuned each time for a different broadcast which makes things hard. ...
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5answers
311 views

A question about super-heterodyne receivers

My question is about the following paragraph: The text implies that the heterodyning process is basically done to obtain a fixed frequency before amplification takes place. Here I don't understand ...
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2answers
90 views

Why do EM waves with longer wavelengths propagate longer distances?

AM radio signals use carrier waves which are quite longer than in FM case. We know that in free space both high and low freq. RF signals should take the same distance in same period of time. There ...
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1answer
57 views

Making a Radio Work

I am new at electronics and I decided to try my hand at making a radio. There seems to be a dearth of material online to actually explain practical radio construction. I built a radio given in the ...
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1answer
81 views

LC Tank Tuner for Super Regenerative Radio

There seems to be very little literature to explain the practical construction of a radio and how a super regenerative circuit actually act as a selector, amplifier, how a antenna is actually to be ...
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1answer
37 views

powering old portable 80's radio with powerbank

I'm trying to connect an old radio to a powerbank. I used the the wires from the 6v battery holder and connected them to a usb cable. Now, when I insert the usb cable into a powerbank, the radio will ...
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3answers
512 views

Short range - low bitrate data transmission under water

I am looking to get a hold of small transmitters for use under water (sea water). They will be rigged to my sensor equipment and attached to fish for scientific monitoring, so size is very important. ...
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1answer
155 views

Improve output quality of FM receiver TEA5767

I have connected a TEA5767 to my Arduino board using I2C and can tune it fine (see instructable.com). As antenna a ~70cm long simple cable is connected. I've connected a cheap 5V amplifier. ...
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3answers
85 views

How can I wirelessly deliver ~30B of data to ~10 peripherals roughly every 50ms?

I am thinking of a system where 10 or so peripherals need to receive 30-50B of data every 50-ish milliseconds (each peripheral gets unique data). The total throughput required might not be huge ...
3
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2answers
175 views

Raspberry PI audio over Cat5e wired ancient hotel intercom

My question is can I (and how might I with minimal insanity) connect the audio output of a Raspberry PI (and/or other USB audio outputs) via say some 10-30m of Cat5 cable to some 10 or so pretty ...
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2answers
60 views

Calculated result for inductance seems wrong?

I'm building an FM radio transmitter kit which includes an LC tank, where C is a tuner capacitor of ~30pF and the resonant frequency is ~100Mhz. The value of the PCB trace inductor, however, is not ...
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3answers
149 views

Radio Frequency Penetration

I've learned recently that lower frequency radio waves travel farther and have better object penetration than their higher frequency counterparts. With this in mind, I was pondering about the ...
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2answers
92 views

Will this short range AM transmitter constructed using crystal work? [closed]

I have designed a circuit as follows: simulate this circuit – Schematic created using CircuitLab There are a few corrections in the circuit. I couldn't do it in the editor because I ...
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1answer
288 views

How to send out 60khz signal from antenna?

BACKGROUND In Japan there are radio-controlled clocks. Time is synchronized by 40khz (in west Japan) and 60khz (in east Japan) radio, which is broadcast from transmission towers. The signal is known ...
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2answers
142 views

Do commercial AM radio stations broadcast a carrier?

A possibly dumb question: I'd like to know if commercial AM radio stations broadcast a carrier tone along with signal sidebands. To ask my question is a different way; if I could measure (view) the ...
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3answers
88 views

College Computer/Electrical Engineering Circuits - Modulating Signal DC offset based of modulating index question

Here is an image of the question. I am stuck at part a, which asks to find the DC Offset based of a modulating index of 0.7, or 70%. So essentially, you will transform the maximum and minimum, yes? ...
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2answers
86 views

RFM69W transceiver - Poor range

I'm having some difficulties with the RFM69W radio transceiver using Arduino Unos with the recommended RadioHead library. I have 2 Unos - each with one RFM69W - successfully sending and receiving ...
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2answers
219 views

Found a part on an old FM transmitter used for tuning. What is it?

This is an old transmitter from the early nineties. The part is the white block with the screw through it. I'm assuming it's a capacitor of some sort, but other than that I don't know much. I don't ...
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1answer
74 views

Which RF Frequency and modulation is best [closed]

We are currently working on a project and we would like to get your advice about which RF frequency and modulation would be most suitable to use for our project. The project is ...
2
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3answers
60 views

Momentary in-line volume control

I'm a volunteer firefighter. We have two kinds of radio traffic. Tones and voice. Tones trigger our pagers, but are also audible when listening to the radio. The trouble is that the tones are much ...
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3answers
44 views

Describing FM inductors

Why, when providing FM radio designs, do people use physical parameters instead of electrical? I.E. 2 turns, 20awg, 2cm dia.
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1answer
89 views

Hint for the way a fm reciever works

As far as I know , a simple AM reciever can consist of a LC filter(connected at antenna) which amplifies the selected frequency, a demodulator( a diode for example) which rectifies the signal,an amp ...