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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3answers
106 views

Frequency Synthesis from 1MHz to 800MHz

I've been trying to plan out a new project for a while. It's a wideband antenna anaylyzer for radio applications. I've figured out most of the details, but the most important part - the frequency ...
9
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3answers
1k views

Are there any open / unrestricted radio frequencies that are free for any use?

The only 'free radio frequency' that I could think of are the HAM radio bands. But they really aren't free, for they are regulated by laws that require you to hold a license, restrict what purpose you ...
0
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4answers
89 views

Can I only use a crystal earpiece for my crystal radio?

I am building a crystal radio for my science fair project, and I am having some issues. For my earpiece, I am using a telephone receiver which may be the issue. For my ground, I am using a water ...
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2answers
59 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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2answers
60 views

How might this RF double pole switch be constructed and perform?

So I'm aware that there are some high speed RF SPDT switches e.g. Single-Pole Double-Throw (SPDT) switch offering 20nS switching time. I'm interested in a switch like the following picture. This is ...
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3answers
125 views

Commnication between mobiles which are in range of 100 meters without using any mobile tower for free [duplicate]

Every mobile radiates its signal to its nearest tower during phone call.Then is it possible for two mobiles to communicate with out using any tower with in range of 100 meters or more .If it is ...
4
votes
1answer
145 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 ...
3
votes
1answer
90 views

Does thhis crystal circuit works?

I need a tiny oscillator circuit for testing an application. Now I haven't much experience in creating oscillators so I would like to use this Collpits-circuit: I only need the carrier wave so I ...
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1answer
49 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. ...
4
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1answer
136 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 ...
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1answer
123 views

What is my best possible antenna setup for a 900MHz 24dBm XBee?

I have two of these 24dBm XBee modules in a semi-LOS setup (1 receiver will be on the ground, obscurred by some tents/structures and other Burning Man camp crap), with these supposedly 3dBi antennas ...
0
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1answer
119 views

What is the pinout on my K F455P 7An filter?

I have a ceramic filter that I'm using for an AM receiver, but I don't know the pins for it. The lettering on it says K F455P 7An. I know that it's a 455 kHz signal filter and I think that it has a ...
2
votes
1answer
224 views

Buffer between high pass and low pass filter when making a bandpass filter?

For a passive filter stage, I want to combine a high pass filter with a low pass filter to create a bandbass filter. Can I just make a simple RC circuit for each and connect them together? Or would we ...
1
vote
1answer
81 views

Choosing a DAC for Amateur Radio applications

I'm looking to make a software defined radio, and I'm currently looking at what DAC to choose. I'm fairly new to this area of RF design, so I don't know what specs to look for. Most of my signals ...
0
votes
3answers
891 views

Can I cut up a proprietary barrel connector cord and make a USB power cord with it?

I have a Yaesu VX-8DR radio, and its power input is a barrel connector. In the age of smartphones, where basically every single device I have uses a USB cable to charge at up to 2.4 amps, I'd like to ...
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1answer
245 views

Making my own radio transmitter

So I have recently been interested in Radio electronics, and I have been looking around to buy a HAM radio transmitter,but they tend to be very expensive (and you learn nothing by just buying it). So ...
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1answer
172 views

If I connected N numbers of amplifiers each have X gain 'dB“ and Y power ”dBm", how to calculate total gain and power?

sorry for bad description, I am a beginner. my question is just for knowledge and I did not test anything. If I connect for example 3 amplifier , each one has 60 dB gain and 15 dBm power. can we ...
3
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4answers
444 views

How should I test a coaxial cable?

I'm a ham radio operator, but haven't been very active on HF bands for a while. I have an inverted-V antenna and a long run (approximately 25m) of coax that runs from my upstairs "shack" down the ...
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3answers
163 views

How to chose an IF, or how bad is zero-IF really?

In a superheterodyne receiver, what must one consider in order to chose an intermediate frequency? Specifically, I'm working on a radio telescope project. It is basically a superheterodyne receiver ...
0
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1answer
53 views

How to determine antenna noise power?

For a 1.4 GHz radio telescope project I'm working on, I need to know the power level of noise an outdoor dipole antenna will be outputting in order to determine the amount of amplification needed. ...
0
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1answer
704 views

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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votes
1answer
287 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 ...
0
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1answer
433 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
139 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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votes
3answers
905 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) ...
4
votes
1answer
394 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
794 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 ...
3
votes
3answers
2k 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 ...
10
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2answers
5k 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, ...
5
votes
3answers
1k 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) ...
4
votes
3answers
221 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
171 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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1answer
3k views

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 ...
10
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4answers
687 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. ...
3
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5answers
607 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
618 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
2k 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. I'...
6
votes
2answers
1k 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
358 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 ...
1
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1answer
245 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.
8
votes
9answers
3k views

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 ...
2
votes
1answer
1k 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 ...
4
votes
3answers
17k views

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 ...
2
votes
2answers
2k views

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 ...
5
votes
3answers
2k views

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 ...
5
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3answers
3k views

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 ...
12
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6answers
459 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 ...