21 votes
Accepted

Is Morse code a digital, binary mode?

According to Shannon (in A Mathematical Theory of Communication - and who's going to argue with Shannon?) there are really only four symbols in Morse, not five: "dit" (defined as one unit time on ...
Jamie Hanrahan's user avatar
15 votes

Moon->Earth 433MHz link achievable digital bandwidth

Short answer: Math says max link rate is 2Mb/s if you knew the perfect channel coding. Which is still an unsolved puzzle. Long answer: You're calculating a link rate. That is fine, and can be ...
Marcus Müller's user avatar
12 votes
Accepted

How does signal strength relate to bandwidth?

It depends on what you mean by "stronger". Ignoring actual limitations of your hardware and just considering the theory of communications, if you have 25 W of transmit power, then you can spread that ...
Kevin Reid AG6YO's user avatar
  • 24.5k
11 votes
Accepted

Do FCC regulations limit digital data rate?

The Current FCC Regulations (as of July 2018) Parts 97.305(c) and 97.307(f) regulate digital modes primarily by symbol rate. The table in 97.305(c) maps bands/frequencies to specific symbol rate ...
Glenn W9IQ's user avatar
  • 18.6k
10 votes
Accepted

Confusion about radio-computer interfaces: TNC, CAT, TRRS, Wolphi Link, ...?

First of all, don't feel to overwhelmed! This can be a bit confusing at the start, but once you understand the pattern and historical development, things will get a bit simpler. So fist of all, you'...
AndrejaKo's user avatar
  • 2,893
10 votes

Is there a legal limit to the bandwidth of a signal used in the amateur bands?

Summary: In all cases, no more bandwidth than necessary. §97.307(a), (b) In data portions of LF, MF, and HF bands, 500 Hz. §97.3(c)(2) In the phone portions of LF, MF, and HF bands, no more than &...
Phil Frost - W8II's user avatar
10 votes
Accepted

Why is a separate repeater required for digital modes? Why can't an analog repeater be used for digital modes?

There is a kind of repeater that can repeat any kind of transmission: it's called a linear translator. It's technically equivalent to an SSB receiver linked to an SSB transmitter. It works for any ...
Phil Frost - W8II's user avatar
10 votes
Accepted

Am I really receiving FT8 signals from 12,000 km away on 144 MHz?

I'd say these are simply corrupt. Take for example: 210113_163545 144.174 Rx FT8 -17 1.3 1247 J06NQY A68ITS/R R QM30 A68ITS doesn't seem to be a real call, ...
Phil Frost - W8II's user avatar
9 votes

GMRS/FRS data communication

The short answer: this is probably technically feasible, but it's not legal. Part 95 of the Code of Federal Regulations is where all the rules on personal radio services (which includes FRS, GRMS and ...
Rafael KR7MJ's user avatar
9 votes

Am I really receiving FT8 signals from 12,000 km away on 144 MHz?

210115_114630 144.174 Rx FT8 -17 -1.6 685 SIDE LOBE This is probably the one real one of the bunch, actually! The odds of random noise decoding as a freetext message with sensible English, ...
hobbs - KC2G's user avatar
  • 12.4k
8 votes

Moon->Earth 433MHz link achievable digital bandwidth

Summary: Theoretical maximum in the neighborhood of 10s of megabits per second. Less than that in practice, perhaps a lot less depending on budget. Let's start with the Friis transmission equation: $...
Phil Frost - W8II's user avatar
8 votes

Can an SSB transmitter be used to transmit PSK?

The short answer is "absolutely!". :-) I started out using Digipan on Windows, but other software such as Fldigi has been released since then. Audio from the sound card to the mic input --and from ...
Mike Waters's user avatar
  • 7,958
7 votes

DMR / DSTAR / P25 Software Encode / Decode

Here is a link to a presentation by Bruce Perens K6BP two years ago: http://algoram.com/dcc2014/AMBE_Exposed.pdf. Start at "Can Hams Use Software AMBE?" I am not aware of any significant changes since ...
Jon Kåre Hellan LA4RT's user avatar
7 votes
Accepted

Can we transfer digital files on radio spectrum?

Radio is analog, and modem converts analog signals to digital signals and vice versa. Everything is analog, yet you can do digital things with the physics that is given to us. As you've noticed, ...
Marcus Müller's user avatar
7 votes

Fast TCP/IP radio modem on UHF band

As you might suspect, the data rate impacts the required RF bandwidth. Besides the data rate, the modulation method, encoding, packet overhead, duplexing, and other factors ultimately determine the ...
Glenn W9IQ's user avatar
  • 18.6k
7 votes

Is Morse code a digital, binary mode?

The mode hams call "CW" is also called "on-off keying" (OOK) - a hint to the fact that it is a binary code. Dots, dashes and spaces are usually sized in multiples of the "dot time": one dot time on ...
Brian K1LI's user avatar
  • 7,848
7 votes
Accepted

Sending a downloaded file on digital: third party communication?

From a Part 97 perspective, the definition of third party communications is: Third party communications. A message from the control operator (first party) of an amateur station to another amateur ...
Glenn W9IQ's user avatar
  • 18.6k
7 votes
Accepted

I configured FlDIGI to dislay letters before my PSK31 signal and then I forgot how I did it

I figured it out. In FLDIGI I had video IDS check marked under Configure/IDS/Video. Here is the link to a video on YouTube that clearly explains what I needed to know. https://youtu.be/nwkz0GNpA0I
user141802's user avatar
7 votes

Has any computer been hacked over amateur radio digital modes?

I know of at least one app that has been hacked based on data received over the air. Because it was done by an ethical pen tester it didn't adversely affect an unsuspecting party, but nonetheless ...
user3486184's user avatar
  • 1,902
6 votes
Accepted

What is "Billion Code" for garage door openers from around 1996?

The billon code refers to a generation of transmitters that could transmit up to ~3.5 billion different codes. Although there were a large number of codes possible, the transmitter always transmitted ...
Glenn W9IQ's user avatar
  • 18.6k
6 votes
Accepted

Is compression "encryption" under FCC regs?

For governments around the world to continue to trust that amateur radio has no nefarious purpose, it is essential that everyone that wishes to, can "listen in" to any amateur radio communications. ...
Glenn W9IQ's user avatar
  • 18.6k
6 votes
Accepted

Relative computational requirement for various digital modes?

Complexity of your question It's hard to make general statements here, because computational complexity is a property of the implementation of a receiver, which usually is a choice given the ...
Marcus Müller's user avatar
6 votes
Accepted

Transmit data over HF signal 10,000km away

What you're asking for is a link budget. For HF, you can use software like VOACAP to estimate path loss. There are several ways you might use the software, but to start I'd suggest: Click the ...
Phil Frost - W8II's user avatar
6 votes

How does a digital demodulator know which level it is reading?

You're asking exactly the right question – my receiver can't know this property of the transmission, how do I figure it out reliably – and that way of thinking makes for good receiver designs :) There'...
Marcus Müller's user avatar
6 votes
Accepted

Can someone without privileges on a band operate FT8 on it using the callsign of a ham who does and is present?

Apparently, yes. See Part 97, Amateur Radio Service Rules: 97.3.a.47 and 97.115.b. The FCC does not appear to make a distinction as to whether the third party is licensed or not. https://www.ecfr.gov/...
timetraveller's user avatar
6 votes
Accepted

What exactly are Gold sequences and how are they used?

Table of contents But what exactly generally is a Gold code? How exactly are they implemented in order to differentiate multiple signals on the same frequency? What Gold Codes are and aren't How ...
Marcus Müller's user avatar
5 votes

Air gapped digital communications mode on VHF?

Suitable, I suppose, though not especially efficient in terms of spectrum or power. Morse code was never really designed for machine demodulation, so unless you also need the ability to decode by ear, ...
Phil Frost - W8II's user avatar
5 votes
Accepted

Open Source Library for Digital Mode

What you describe is Software Defined Radio! Hurray! So, everyone having read my answers knows: I'm a GNU Radio fanboy. GNU Radio has to be understood as the Free&Open-Source LEGO of Software-...
Marcus Müller's user avatar
5 votes

Pre-transmission burst sent by fldigi

That's a Reed-Solomon identification (RSID). It's purpose is to tell other stations what mode you are using. For PSK it's usually pretty obvious. To disable it, look for the "TxID" button in the ...
Phil Frost - W8II's user avatar
5 votes

What is the minimum equipment necessary to get on the air with FT8?

Without getting into specific product recommendations, I believe the simplest way is as follows: Obtain a license. An amateur license is required for using amateur bands. I am not aware of any non-...
Chris K8NVH's user avatar
  • 1,042

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