Open IP over VHF/UHF
rowetel.com
rowetel.com
So if you research learning materials for those licenses you’ll be off to an awesome start. There’s excellent free and paid books available.
You’ll learn how to build a basic fm radio using gnuradio along with other cool stuff, like a simple explanation of decibels among other things.
Lots more recommendations here: https://news.ycombinator.com/item?id=14584377
Some DSP books (Like Proakis's) are incredibly long-winded and totally detached from the real world (and I say that as a theoretical physics student) and don't cover the sampling topologies that many SDR's use.
Interestingly, I have some very old communication theory books from the 50s and 60s - they are still useful for Software Defined radio stuff today. The only thing they didn't foresee is the throughput of a modern digital filter being as high as it is.
However, digital TV is allowed. Some folks have circumvented the rule by sending a low bitrate video stream as a small part of their overall data.
The article is using FSK with a bandwidth of at least 300 kHz, so it's not legal in the US (for data only).
In theory, you should be able to run 780p in a 6 MHz wide channel in the 430Hz band, or even squeeze 480i down to fit a 2MHz wide channel. (The max bandwidth allowed for amateur video in the USA on 430 is 6MHz, DVB-T does have 8MHz wide formats used in some countries for broadcast.)
Contact KH6ATV if you are interested in doing some experiments. I recommend reading his notes first: https://kh6htv.com/application-notes/
For those that haven't stopped reading already: DVB-C -- optimized for cable. DVB-S -- optimized for satellite path loss and fading, but not for multi-path. DVB-T -- optimized for terrestrial paths which may suffer from significant multi-path propagation. ATSC -- The US standard, which unfortunately was standardized earlier than the rest and is expensive to generate and has outrageously poor weak-signal performance, both of which make it a ridiculously bad choice for amateur radio.
GNU Radio is also capable of transmitting DVB-S, DVB-S2, DVB-T, DVB-T2 and cable TV 64QAM/256QAM. With DVB-T2, you can even send a MIMO (actually MISO) signal with dual TX SDR's.
I agree that these things should be kept off the air, but I don't think it's a "money talks" situation.
FCC/CRTC: On July the 1st at 14:00 you transmitted an undecipherable message on 28MHz.
Amateur Radio operator: I used y-modem protocol to transmit an image using 7P1 (7bits Parity 1 Stop bit).
FCC/CRTC: but's that's stupid! Nobody has used that in 40 years!
AMO: But it wasn't encrypted. Good bye.
- Use rare/odd frequencies that are hard to access with commercial off the shelf gear
- use esoteric modes and modulations (like you mention)
It's hard for me to imagine that they have an army of radio engineers to go looking at all signals, figuring out which ones are "undecipherable", physically identifying the transmit locations and then determining who did it.
The entire culture works hard to weed out anybody that doesn't follow the rules. If you do something you're not supposed to, there's a good chance someone will figure it out and report you.
Foxhunting is a sport for them.
Its especially common these days with the advent of software defined radio, spectral displays and large amounts of storage for operators to come across a strange transmission and record it for further analysis, often posting in forums and sending the recordings to other people for them to try and analyze it.
And some times those recordings are sent to the FCC and the FCC sends out strongly worded letters.
If it really gets bad, the FCC will act and IIRC they average about 20~50 or so fines a year.
Even the DTMF tones to control repeaters aren't encrypted. Some repeaters do obscure the re-transmission of the DTMF codes by muting the output, but this is legal.
To clarify what percentage of your clubs repeaters are reachable through one or more encrypted connections?
Sailmail is super valuable for its users, but is breaking the rules in various ways. I’ve been a user and am also a ham.
"What's the difference between encryption and steganography? You don't know."
Plausible deniability.
Amateur radio enjoys the privilege of pretty lax regulation, largely due to the players not making any trouble. Speaking as a fellow radio amateur, we don't want our hobby ruined just because someone wants to be a troublemaker.
What. You literally have to have a license issued to you personally (no anonymity) by the government to even be allowed to do it. And the rules of what can and can’t be sent are, to my Internet-accustomed mind, excruciatingly onerous. No encryption? No foul language?
1. You need a personal license to identify you, as an operator of a radio station. This is similar to how radios on ships and airplanes work - you need to be able to identify every transmission (even cellphones are uniquely identifiable). This is not only part of the entire sport (we're trying to contact and identify each other), but is also used to identify problems.
2. Just like for airplanes and ships, there are some rules to what you can transmit, as your transmissions can be heard (and cause troubles) for tens, hundreds and even thousands of kilometers away.
3. You have countless frequency allocations available, all over the spectrum, despite the scarcity.
4. Unlike everyone else, holding that license permits you to build your own equipment and transmit with kilowatts with no certification needed. It's extremely easy to cause massive issues with this, such as interrupting cellular communication/gps/wifi an a large area, blowing up your neighbors stereos, and fun things like that.
There's a reason that everything else needs to be tested, certified, and require dedicated band allocations - we avoid it by showing that we have the sufficient skills to practice our hobby and not cause trouble.
Unlike everyone else, we can do pretty much whatever we want as long as we keep it around a kilowatt and talk nice. I consider that to be extremely relaxed rules.
- General Mobile Radio Service (GMRS) which is limited to a set of frequencies in the UHF band, 50w repeaters, and a few watts handheld, and requires an $80? license.
- Family radio service (FRS) which is limited to store-bought handheld units with 0.5W maximum output
- Citizens Band radio which is limited to 40 channels at 4 watts and is highly abused by its users and relatively unenforced
- Multi-Use Radio Service (MURS), which is limited to a six VHF channels and 2 watts and shared with many users
- Business Band/LMR Part 90, which is licensed and regulated for business/commercial use with many other shared users
- Microwave, which is licensed and heavily regulated
- Broadcast radio, which is licensed and very heavily regulated (and is one-way only)
None of these services allow you free reign over a wide spectrum of radio with home-built equipment for the purposes of experimentation and recreation, except for the experimental license, which only allows you specific frequencies, power limits, and other regulations based on your license application and grant.
I agree that amateur radio regulations are relatively relaxed, if not very generous, liberal compared to the other radio services.
Those rules about absolute identifiability are only “part of the entire sport” because you have defined it to be that way. What if Internet chat had been defined the same?
Also, enumerating what you are allowed to do once you are granted a license does not help the argument that the requirement for a license is oppressive.
> There's a reason that everything else needs to be tested, certified, and require dedicated band allocations
Maybe there were reasonable technical reasons in the 1970’s, but now with modern technology, there should be no problem, or at the very least significant relaxations of what the regular public is allowed to do.
I repeat: Having to get an individual government license to practice your hobby is draconian. But, of course, regulations don’t really ever get less restrictive.
Secondly, the original argument was that, and I quote, “Amateur radio enjoys the privilege of pretty lax regulation”. And a requirement to get a government license, tied to your personal name and identity, gated by a large fee and difficult exam, is not my idea of “lax regulation”.
As to the difficulty, children at about 5 or 6 have passed the Technician class test. It takes some studying, but it is really easy. The most difficult part is in understanding the bands that you're permitted to operate on.
In reality, getting a license is easier than it's ever been. There are no more requirements for Morse Code - though some still use it. There is no longer a requirement to go to an FCC field office for testing - your local Ham Radio club can give you the exam. It used to be that you got your Novice ticket, and had to upgrade to Technician within a fairly short period of time - now you begin with the Technician exam.
As for the regulation, there is a real legit reason for this. As Amateurs, we're permitted to operate on a wide range of frequencies - some of which are close to those used for Radar, Wi-fi, and many other services. Some of the frequencies we can use are very long range. The reason for the regulations that exist are in order to prevent interference to other services, to avoid breaking international treaties, etc.
The technical knowledge is important because you're permitted to build your own equipment. It's important, if you do, to know that your equipment is operating properly, so that you don't disrupt many other services with transmitters that are spewing noise and harmonics on many unintended frequencies.
In short, Amateur Radio is FAR LESS regulated than any other service, because of the technical abilities that we have historically displayed. It's a worthwhile hobby and lots of fun. I don't know of any other hobby that has its own satellites in orbit, that has bounced radio signals off of the planet Venus - and regularly uses the Moon or even ionized meteor trails as a reflector for radio signals...
Seriously, given what we can do with the hobby, passing a relatively simple test and paying $15.00 to get your license - and no recurring annual fee ... I don't consider that restrictive at all.
There are places you can use secure communications, for example in the ISM bands (like wifi) or you can license a chunk of frequency for your own use.
Still, very cool.
Fascinating stuff.
People have been able to eavesdrop on homes by targeting pretty much anything containing metal coils (including appliances) with advanced HAM radio equipment since the early 1970s.