Consider also the rf tag.

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0
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2answers
58 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) ...
3
votes
1answer
77 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 ...
-2
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2answers
113 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 ...
1
vote
1answer
144 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 ...
0
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2answers
55 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. ...
3
votes
5answers
262 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 ...
5
votes
2answers
62 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 ...
1
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1answer
53 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 ...
0
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1answer
49 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 ...
1
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1answer
31 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 ...
6
votes
3answers
473 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. ...
0
votes
1answer
56 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. ...
3
votes
3answers
82 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
votes
2answers
119 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 ...
1
vote
2answers
56 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 ...
2
votes
2answers
93 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 ...
0
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2answers
70 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 ...
0
votes
1answer
195 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 ...
1
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2answers
140 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 ...
0
votes
3answers
71 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? ...
-3
votes
2answers
62 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 ...
2
votes
2answers
202 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 ...
-2
votes
1answer
65 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
votes
3answers
55 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 ...
2
votes
3answers
42 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.
0
votes
0answers
35 views

output impedance CC1125 transceiver

I am trying to obtain the source impedance on pin 19, the datasheet says it is 50+j30 Ohms at 433MhZ. I am not sure if that's including the external circuitry to match it to 50 Ohms or if it's on the ...
1
vote
1answer
83 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 ...
1
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0answers
72 views

FM radio Transmitter - frequency drifting

First can someone explain to me how this FM transmitter circuit work? Second, after replacing Q2 with a blt81, I got a Frequency drifting problem. Once it's running for a while, I need to re-tune my ...
2
votes
2answers
91 views

How to make radio reception better with antenna 133 cm long [closed]

My low cost FM radio receiver Philips MCM129 is not receiveing some radio stations well. It has antenna made of about 133 cm long thin insulated wire which I suspect is the rason of the problem. Can ...
3
votes
2answers
162 views

What happens when you keep increasing frequency of an RF signal?

I know that radio waves occupy the lowest portion of the EM spectrum and gamma rays occupy the highest. I'd like to know if increasing the frequency of a radio wave can produce visible light and maybe ...
0
votes
1answer
104 views

Why am I losing the signal when I attach this RF amp circuit and how can I correct it?

I am trying to follow this circuit diagram: Taken from (http://www.techlib.com/electronics/crystal.html) Using two oscilloscopes I am watching the signal on the tuner circuit and the voltage ...
1
vote
1answer
48 views

Ionic Reflection [duplicate]

I finally went and got my Ham Radio licence. I've been reading about how radio operators use the ionosphere for long distance communication through ionic reflections of transmitted/received EM waves. ...
2
votes
2answers
69 views

Satellite detector and a mobile phone

A satellite dish with LNB connected to a satellite detector when powered by a 18v source could detect radio waves from satellites. I made one using the ppt here. The detector, (when it was not ...
5
votes
2answers
420 views

How do compact AM radios establish a ground?

I am trying to construct a radio and, at the first stage, I have finally detected circuit a signal. My previous attempts have failed and I have discovered that it is because it was not properly ...
1
vote
1answer
94 views

Is my oscilloscope affecting my tuning circuit?

I am building an AM Radio and I have constructed a tuner circuit. See below. simulate this circuit – Schematic created using CircuitLab However, I cannot use this circuit, because even ...
0
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0answers
70 views

What Type of RF Antenna Connector is This

Could you please help me identify this connector. The connector is from a walkie talkie antenna operating at 141MHz. The pin broke off and stuck inside female receptacle. I would very much like to ...
1
vote
2answers
94 views

Difference between RSSI and Received Power

Is Received Power and RSSI same thing? I have been looking into it and think they are the same. But please guide me the difference between them if they are not the same.
8
votes
2answers
545 views

Why are radio signals clearer near the human body?

In Asia, specifically in Bangladesh, we often listen to FM radio. But the signal is not clear everywhere, that means it produces some noise. From my childhood till today, I have observed that, if I ...
-1
votes
1answer
41 views

Location transmitter [closed]

I want some advices about a radio transmistter,actually this radio trasmitter is more a location transmitter which transmits at about 512Hz.I want to know how could i design a transmiter and a ...
1
vote
1answer
89 views

How can I maximize the amount of energy an antenna is receiving?

Bear in mind that I am very new to electrical design and have only a beginners level circuit course under my belt. I am trying to build an AM radio and although there are a lot of tutorials out there ...
0
votes
1answer
101 views

How to calculate capacitance and resistance for this simple A.M. radio?

\$v_i\$ is the A.M. signal, \$v_o\$ is the modulation wave. How do I calculate the optimal capacitance and resistance, for a given carrier wave frequency? If there isn't necessarily an "optimal" ...
1
vote
2answers
59 views

Can an RF module be used for ZigBee?

I am very new to wireless communication protocols so please excuse me if this is a silly question. I am using a PIC to communicate between two Zigbee modules. However I also own a 2.4GHz RF ...
3
votes
3answers
602 views

FM transmitter design?

I stumbled across a relatively simple FM radio transmitter online. Credit: makezine.com I wanted to understand how it works (it is called "super simple" on the website), but several hours I have ...
0
votes
3answers
54 views

Techniques for Attenuating a 5GHz Signal Between?

I need to set up to radios with high gain directional antennas to talk to each other within a relatively small distance. The radio in questions is a RADWIN 5000 jet. The max distance I can set them up ...
8
votes
4answers
435 views

FM Carrier Wave Generation

I'm trying to understand how the following FM radio schematic works. Specifically, I want to know how the carrier wave is generated. I understand the concept of an LC tank and I think I see it ...
37
votes
8answers
5k 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 ...
2
votes
1answer
129 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 ...
4
votes
1answer
104 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
81 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
226 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: ...