Electrical Engineering Stack Exchange
Electrical Engineering Stack Exchange

Questions tagged [ham-radio]

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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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, such as the portable one sitting on my desk, do…
Stephen Melvin
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Amateur radio practice exam question about voltage drop

So the question is as follows: "Your mobile HF transceiver draws 22 amperes on transmit. The manufacturer suggester limiting voltage drop to 0.5 volt and the vehicle battery is 3 metres(10 feet) away. Given the losses below at that current,…
Mohammad Ali
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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 I have done to date turns up things that…
Rick_2047
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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. When you install the antenna mount kit though, you…
Chef Flambe
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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 can use them for, and are governed by some…
Lyle
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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 for rejecting that noise. Here's an example of such…
Phil Frost
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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 operate it with a laptop can be used to transmit…
Vesa Linja-aho
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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) is introduced to the LC circuit either through a small…
user17592
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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 than 100 miles... Why does this happen? Is it…
Everyone
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Tube transmitter tuning

I am trying to tune/tweak/repair this transmitter for a friend of mine. It is oscillating, and it has rf power on the antenna, but it just doesn't seem as "strong" as it should be. The diagram says 35-40 watt carrier. Now its a class A final amp,…
McMurdo
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Ham Transceiver to computer Interface design question

I am building a Ham transceiver to computer interface, which has the RS232 port controlling the PTT on the radio. The circuit currently calls out for a 1.2K resistor in series with the RTS line and the 4N25 optocoupler's input. If I use a 4N35…
Chipresistor122
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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 feed it Morse code audio and for it to transmit that.…
Brad Hein
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What is the best radio protocol for long range serial communication?

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 this but what would be the best protocol in this use…
user12242
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BJT Clapp Oscilator for 3-6MHz

I designed a Clapp VFO to aid in my Ham Radio projects (Non-superhet SSB and CW recievers for 80M and hopefuly 40M). I chose the clapp topology for it's frequency stability. I want it to tune at least from 3.2MHz to 4.2MHz and have low harmonics.…
thegamebusterpl
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What is the purpose of diodes after RF power amplifier and before LPF?

I am planning to build an RF transmitter using an integrated PA module (RA30H1317M1). While studying schematics of similar transceivers, for example IC-2200H (that also has a PA module) I see all typical transmit chain components like the PA,…
filo
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