Ham radio (also called amateur radio) is a licensed form of radio communications for private and non-commercial use. Frequency allocations are made available specifically for ham radio and power levels allowed are typically much higher than available in unlicensed areas of the spectrum.

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How to tune a radio receiver using a crystal oscillator?

I'm building my first radio receiver (a simple Ramsey HR-40 kit). The "Alignment" section of the instructions requires that I have some other device which I tune my receiver to. Since I have no such ...
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70 views

VHF radio - Motorola GM340 - could I have damaged it with too much current? Why would it not be damaged by being connected to a 12v battery? [closed]

I connected a Motorola GM340 VHF radio to the 12v DC converter for another radio, an ICOM IC78, which gives 13.7v at 16 amps. The wiring did not have a fuse. As it did not work, I wonder if the ...
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57 views

Separate antenna for radio transmitter and receiver

I am building a HAM radio. Do I need a separate antenna for transmitter and receiver? I will be using 20m band and voice communication (No Morse code). My primary requirement is that I should be able ...
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1answer
65 views

Using filters to reduce bandwidth of received signal

I am doing some radio work, and I assume you can use a bandpass filter to reduce the bandwidth of a received signal. The application is modifying schematics for a FM broadcast receiver to a 5-25 kHz ...
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2answers
220 views

Duplexer for portable VHF repeater

For my undergrad EE capstone project I'm designing and building a 2m band analog amateur radio repeater. Our design goal is to build a solar-powered low power repeater (something like 5-20 watts) ...
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1answer
170 views

What is the best radio protocol for long range serial communication? [closed]

I'm working on a project that would require up to near time (<=5mins) of packet base communication over Long Distances of upwards to 80 Gm. Obviously the base station would have to be scaled for ...
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1answer
263 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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3answers
644 views

Reverse engeneering a home automation RF 315Mhz transimtter

I have this remote control and transmitter and I want to reverse engineer the 2 RF signals sent by the transmitter. This is the board. The board says "ak-rk01se". I can also open up the transmitter ...
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590 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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3answers
395 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
170 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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153 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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What, if anything, makes shielded loop antennas so great at rejecting local noise?

There is a folk wisdom, among amateur radio operators, that if you have a lot of noise on HF, such as in an urban location, then using a shielded magnetic loop antenna for receiving is really great ...
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0answers
83 views

Does skin effect distort a transmission pattern?

This question got me thinking. Homebrew ham-radio antenna is typically a monoband contraptions; perhaps SWG 16 through 21. Thinner wire is more resistive, but at HF/VHF skin effect comes into play ...
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4answers
383 views

Why can a feedline be cut randomly when the antenna needs a specific length?

With a mobile two-way radio you have the radio, an antenna mount kit and the actual whip antenna. The antenna needs to be trimed to the correct length so to match the freequency you are Tx/Rx on. ...
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4answers
280 views

Troubleshoot Crystal Radio

Alright, I'm totally confused. I have built the following circuit with absolutely no result, not even a click. Even after reading through several other similar questions on the board, I haven't ...
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5answers
422 views

Does CW or SSB consume more power?

CW pumps out the full carrier but has a better SNR. On the other hand SSB suppresses the carrier, and one side-band but this suppression demands additional circuitry. There are probably additional ...
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2answers
944 views

building a 900Mhz long-range data communications network

First to be clear: I am a licensed amateur radio operator with about 10 years programming experience and I took electronics in high school (2008). However I tend to stay on the soft side of things. ...
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1answer
416 views

Why does the ionosphere reflect HF but allow VHF signals to penetrate through?

Wikipedia says: ... Unlike high frequencies (HF), the ionosphere does not usually reflect VHF waves (called skywave propagation) so transmissions are restricted to the local radio horizon less ...
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2answers
198 views

VHF: power resistor to replace dummy load

I need to check a VHF radio installation @ 155 MHz. For these purposes there exist fairly expensive dummy loads. Can I just use an ordinary power resistor soldered with short wires (3cm) to an ...
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1answer
204 views

Can Grid Dip Oscillator (GDO) detect WiFi, Bluetooth and NFC?

Can I use GDO to detect those waves? Can I buy one somewhere or I need to build one? I would to have digital one, that will just show the frequency of the waves.
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6answers
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Does there exist an internet-like peer-to-peer packet radio system?

Has anyone designed a peer-to-peer communications networks system, which works almost like the internet, but wirelessly? I mean a system, which: you can connect the transmitter to an usb port and ...
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1answer
804 views

Help with PTT circuit for icom radio

I'm trying to set up an APRS station using an old icom HT. Receiving is fine, but I'm having some trouble with the transmission side. When I connect all my parts together, the transmit light ...
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4answers
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How do I estimate the transmission distance of a 50 watt 2m radio?

Can anyone point me to a reference for calculating (estimating) the transmission distance of a 50-watt, 2-meter radio? The transmitting antenna will probably be 5-7 meters above ground. Probably the ...
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2answers
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Designing a simple CW transmitter/receiver

I'm interested in building my own radios for use on the air. I'm still rather new to electronics so I'm looking for simpler projects that I can build to learn on the way, and I'm thinking that a CW ...
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1answer
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What determines the transmit frequency in this 555-based transmitter?

I'm a general class ham, and am just starting to do my own homebrewing. I was planning on basing a QRP transmitter off of this instructables project, seeing as I have a veritable plethora of 555 ics ...
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How to build cheap radio propagation beacon?

I want to build a Radio Propagation Beacon but I would like to find an integrated circuit that does most or all of the work of the transmitter. Transmit to 28Mhz (Ham 10-meter band) Allow me to ...
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6answers
415 views

Getting started in Ham radio

It's been quite a while since I heard about amateur (ham) radio. I think it's a good hobby to dabble into to develop an understanding of communication technology and electronics. But whatever research ...