Hacking Ham Radio for Texting | Hacker News Reader

Hacking Ham Radio for Texting

spectrum.ieee.org

I think if this interests you, you'll like the LoRa-based devices better. They're unlicensed, so you can encrypt, use it without a ham radio license, etc. LoRa is pretty proprietary which is evil and all, but the end result is good.

Hackaday has some good example projects:

https://hackaday.com/2020/04/25/a-lora-im-me-for-the-end-of-...

https://hackaday.io/project/171790-armawatch-armachat-long-r...

Came here to post this; also, https://meshtastic.org/. Still in (very) active development, but it genuinely works quite well and is very exciting.

Imo lora and similar protocols are a great example of the innovation fueled by the existence of the ISM bands.

https://www.f3.to/cellsol/ This one is geared towards low power consumption, for throwies.

Technically we could build something like LoRa on the amateur bands. It's a pretty basic protocol with up/down chirps.

With the kind of power we can use compared to the ISM bands this kind of robust protocol would have a huge range.

To some extent, modes like FT8 have shown how effective modern encoding techniques can be. The problem, I suppose, is that FT8 is ridiculously structured; optimizing to the core the bare necessities of a QSO. I think that is probably the reason for its success; if I want to talk to people, it's easy to find them on the Internet. But accumulating QSOs is an achievement in and of itself, and something you can only do with ham radio, so the optimization is probably perfect.

As someone who's had the most ham radio success with FT8, I do find myself asking "what if there is an emergency"? I probably won't have power for my computer, and WSJT-X is pretty cumbersome to use while mobile. So we should probably be looking into other technologies, but the old standby CW seems good enough, so nobody is really looking.

Have you looked into JS8CALL? It uses the same bones as FT8 but allows for longer exchanges.

Texting via APRS has been a thing for about 20 years. It's also a fantastic way to publish both your phone number and the numbers of the people you are texting in an easy to skim format. Digital modes is one of the areas where the HN crowd could introduce significant advancements to Amateur radio (while pissing off all of the older HAMs who just want to talk about the weather on 40m).

And before APRS we had packet radio[1]. Around 1992/3 I remember going to Boy scout camp at ten mile river and a scoutmaster from another troop had a packet radio setup connected to a luggable PC in one of the buildings. I dont remember what it was for but the idea of wireless digital communications was exciting. Now its everywhere.

1. https://en.wikipedia.org/wiki/Packet_radio

APRS is built on packet radio (AX.25 protocol IIRC).

It's safe only because nobody cares enough about ham radio to bother skimming anything.

I've been pushing for encryption for years but just posting this well get a bunch of elmers posting upset replies.

It's frustrating constantly being under the thumb of a generation that will not yield to progress

How would encryption work?

Encrypted communication is not allowed on the ham radio bands.

One could still run a numbers station? There's no way to prove the code words have any meaning beyond what is obvious.

> One could still run a numbers station? There's no way to prove the code words have any meaning beyond what is obvious.

I'm not so sure one could, legally. A number station would broadcast regularly a one-way communications, with no clear meaning. Here's an excerpt of the law from FCC part 97, which is actually surprisingly short and readable. It prohibits:

"messages encoded for the purpose of obscuring their meaning, except as otherwise provided herein; obscene or indecent words or language; or false or deceptive messages, signals or identification.

(5) Communications, on a regular basis, which could reasonably be furnished alternatively through other radio services.

(b) An amateur station shall not engage in any form of broadcasting, nor may an amateur station transmit one-way communications except as specifically provided in these rules..."

https://www.ecfr.gov/current/title-47/chapter-I/subchapter-D...

That’s a sure way of ending up with several old men yielding yagis like swords descend upon your house.

FCC rules won't allow encryption. I'm not sure why the rules were made originally.

Ham radio relies on self-policing within the community to ensure compliance with the rules - the biggest one being "no commercial use".

The "no commercial use" rule ensures companies aren't using the limited ham radio spectrum as a workaround to getting their own dedicated license and frequency allocation.

If encryption were allowed, there'd be no way for other users to verify whether traffic is commercial or not.

I always thought that encryption not being allowed was a way to discourage illegal commercial use of it.

No business wants their comms in the clear with no means of verifying the sender of the message - so ham radio would be useless to them.

But even not-for-business, I don't want someone else to be able to impersonate others, so signatures/verification still needs to be supported. Otherwise someone who's good at voice impersonations of others could wreak havok.

There is no rule against using digital signatures for authentication. Your actual message just has to be in the clear.

The exact wording is in 97.113: "No amateur station shall transmit... messages encoded for the purpose of obscuring their meaning".

Because way back when long range radio was a plausible way for spies to communicate back to the homeland.

Encryption is indistinguishable from noise. So the difference between a high power encrypted transmission and high power jammer is semantic. Radio transmissions also propagate. Sometimes they propagate in unexpected ways reaching much farther than expected.

If you combine these things you end up with encrypted transmissions raising the noise floor for everyone in a band with no way to know if that noise is a transmission or actual noise. A lot of ham bands are already very noisy from natural sources, a bunch of encrypted transmissions increasing the noise floor just serves to make those bands inaccessible.

The propagation makes this problem even worse because encrypted transmissions can raise the noise floor for hams hundreds or even thousands of miles away. Even if an encrypted transmission uses a very narrow bandwidth (no worse than other digital modes) you're still monopolizing part of a very small band with a private conversation preventing others from using the shared resource.

To make matters worse encryption necessitates some form of error correction. Whether this is forward error correction, retransmission, or whatever it's necessary for a receiver to receive a correct ciphertext in order to decrypt a message. Error correction necessitates a higher duty cycle in order to send the error correcting overhead. So encrypted transmissions last longer than the equivalent unencrypted digital mode tying up limited bandwidth for a longer duration.

> Encryption is indistinguishable from noise. So the difference between a high power encrypted transmission and high power jammer is semantic

The difference, from an RF perspective, of an encrypted signal and a non encrypted signal is non-existent as the encryption takes place before the modulator. Therefore encrypted signals won't impact the noise flow for everyone in the band. This would only occur if the operator were using frequency hopping.

>you're still monopolizing part of a very small band with a private conversation preventing others from using the shared resource

Depending on the technology used in the receiver, this also isn't true. There are numerous techniques to allow for multiple carriers on the same band. CDMA for example would allow for this. It would take some coordination to make sure each carrier is using a different code but should be feasible for amateur radio operators. It all depends on how sophisticated their receiver is.

>Error correction necessitates a higher duty cycle

This is true and is why encrypted signals have lower data rates. So instead of having a longer transmission you lower the data rate to get the same effect.

Ham bands are pretty small. Like the two most popular HF bands are only 300-350 kHz and not all of them are allocated for voice.

> Therefore encrypted signals won't impact the noise flow for everyone in the band. This would only occur if the operator were using frequency hopping.

While the encrypted transmission will look like a regular digital mode the fact it can't decrypt the decoded symbols means it's effectively noise. Ham bands are for all hams. There are innumerable other ways to have a private conversation with targeted recipients.

> Depending on the technology used in the receiver, this also isn't true. There are numerous techniques to allow for multiple carriers on the same band. CDMA for example would allow for this. It would take some coordination to make sure each carrier is using a different code but should be feasible for amateur radio operators. It all depends on how sophisticated their receiver is.

Ham bands already have de facto CSMA, you wait for open air to transmit.

I am hoping they explained why.

Most people who complain about the encryption regulation just completely disregard the reason for encryption in the first place (ie, all other regulations become unenforceable if encryption is allowed).

Do they? Maybe we need to figure out the essential subset of regulations that preserves the most essential aspects of the system while still permitting encryption.

I have no doubt it will be a huge mess and take a few tries to get right.

We should get started already -- if we don't, HAM will die, and it will deserve to die.

Mostly. Ham is meant for play, not as a primary means of communication or for commercial purposes.

If everything is encrypted, how could you tell? How could you even tell that the users were licensed?

By not encrypting the call signs because unencrypted call signs aren't the problematic restriction. It's the content restrictions that are stifling in the modern world.

Also: progress has changed the landscape. HFDF used to be difficult for the military but now it's easy for hobbyists, and not just in last-mile form, but in coordinated always-on infrastructure form. The regulations were not written with this in mind. With an active community this fact alone might obviate the need for many a regulation.

And I'm not broadcasting my legal name and mailing address so i can "play" with radio transmissions.

The unenforceable argument isn't really a thing. If we look at some common encryption standards, the call sign is in the clear as it has to be for routing.

In the case where someone is swearing with their friends over an encrypted channel, it's just not a problem, no child will hear the swears without a quantum supercomputer.

In the case where a business is illegally using ham bands to avoid paying license fees, they can already do this, nobody is actually checking. You can encrypt P25 on the bands all day long because nobody has radios that work with that digital mode and nobody will spend the time running signal analysis to figure out that A) it's P25, B) it's encrypted and C) where it's coming from. If it became rampant the FCC has the tools to very quickly figure out all of these things and if the broadcasts don't have a call sign and are coming from a business premises then it's obviously breaking the law anyway.

If it could be a problem, it already would be. All the Chinese digital business radios support encryption now. We're just not allowed to use it because people are scared of bogeymen

Yes, people are checking. Repeated abuse of ham radio (in the US anyways) will eventually get enough hams mad that they will report to the FCC, which does investigate and crack down from time to time.

No, it isn't an instant 100% chance of retribution.

People are checking FM because it's trivial. I have yet to hear of someone getting caught using digital encryption entirely through band monitoring (ie not doing something obviously stupid elsewhere like bragging about it on social media)

It's 2021... ham operators hear someone using the band for something digital, and then use the one of the many cheap SDR sticks to check what is using the channel.

One call to a regulator, and it's done.

I think it's also because ham radio is supposed to be shared experimentation. Part of this is hearing someone trying something out and replying.

If everyone starts chatting with their friends on encrypted channels, we don't really have a community anymore. It was never meant to be a private chatbox.

I think it should be a bit less rigid in this day and age though. For example it should be allowed to use encryption for authentication purposes IMO. It's too easy now on digital modes to fake someone's callsign. Brandmeister has built some cool stuff with one time password but more complex authentication mechanisms aren't allowed. Apparently the FCC allows an exception for this but not every country does.

Don't conflate "it's extremely obviously not legal" with "people don't like it" (the latter camp you can always ignore, they fundamentally can't do that much in most cases except not support you. See e.g. the whining about pretty much any digital mode ever). But encryption on ham bands falls in the first bucket, which is a problem, and I doubt that's simply a "we need to advocate for changing it" matter.

Fun fact: in parts of the world, you can transmit pretty much whatever you want on CB, nobody is stopping you from running encrypted digimodes there. And for slow transmissions, one can probably squeeze something through ISM bands, despite the limitations there.

And you probably could develop a good mode on ham bands that has the foundations and does signatures but not encryption, and can switch to encrypted on other bands.

I have yet to hear what “progress” encryption enables that operating via and open protocol doesn’t.

Unfortunately the FCC's rules around the Ham bands and digital modes ends up restricting a lot of potential for advancement and experimentation.

That and anyone using this would need a ham radio license

IMO that's a great way to set up a sandbox: it has built in crowd control and a mechanism to keep out flagrant abuse.

Yeah, it doesn't scale to the moon, but that's the whole point: it's a proving ground, not a moon rocket.

It's not that it doesn't scale - it's just there's a reason people use letters to communicate and not postcards.

People expect a modicum of privacy which ham radio, to its detriment, denies.

It also completely prevents any interesting radio experimentation. There isn't anything left on that frontier that couldn't be conflated with encryption.

As someone who once believed this, this statement is simply not true. Experimentation in ham radio is largely about the physical layer, with maybe some layer 2-4 work when it comes to building low-scale communications infrastructure. Encryption is not implemented at this level, and the limitations on encrypted content do not impede research into new digital modes or actual radio science.

I think it is worth asking why modern digital radio standards (e.g. P25, DMR, LTE, 5G) were largely developed outside the ham community. My survey level understanding is they came from the communication needs of their users and are not a natural evolution of something that hams would build, with or without encryption. When I was researching DMR, there's a lot of stuff that is unnecessarily clunky when considering the use case of a ham QSO. Conversely, the business users of DMR want more structure than what's provided with amateur-designed digital modes. With 5G, I think there are some real technical and capital barriers, i.e., very few amateurs have access to the grade of test equipment needed to engineer and experiment with systems at those frequencies.

To your first point I think you are missing their meaning a bit. There is actual encryption, like AES. And then there are communications methods that aren't open by default. The way in which the FCC regulations are penned means Ham transmissions can't be private in any way. So no just actual encryption but pretty much anyone with a compatible transceiver should be able to listen in to what you are saying at any time.

That level of permissiveness can be problematic because some technologies are by their nature not compliant. FHSS comes to mind. Its not encrypted but if you don't know know the sequence it might as well be. WiFi, bluetooth and most cell protocols use FHSS. So if you wanted to experiment with digital data transfer and make it in any way robust in a congested area you could not do so as a Ham. Its implicitly illegal.

To your second point I agree. DMR, P25, TETRA etc were developed with police departments and such in mind. To get the full use out of them requires a heavy investment infrastructure for trunking systems. And their programming models assume a set it and leave it use case where the operators are not trained or even savvy to RF comms.

This makes them at best clunky for Hams. DMR has caught on not because its the best, but I think because its easier and cheaper for radio makers to license it. In Europe Type 1 is also allowed unlicensed which gives the market momentum.

What's more conflated with encryption than e.g. the level of encoding you find in DVB-S or FT-8?

Ft-8, jt-9, jt-65, and wspr all break the rules when on 60 meters.

No one cares...

You're only allowed to transmit square on center of the allotted channels, and, this is the important bit, one person at a time. All the modes that JT invented flat out ignore both rules for 60 meter transmissions.

I don't care, but I get sick of people telling me that my pactor modem is "illegal".

60m in the US I guess, where it's a very restricted secondary use of a military band. That's quite a special case.

Also these modes being ok or not on 60m has nothing to do with the question I asked?

FT-8 has issues beyond what is or is not encoding that could be argued (and is) to be in violation of certain rules.

Ham radio is not meant for that though. Its expressly meant for education and scientific experimentation by amateurs. What it actually gets used for is Boomers chewing the fat and LARPing as emergency services dispatchers mostly but the allocations were put in place to allow people to connect with one another and learn the science of RF in a practical way.

The sad part is that the FCC has been more interested in maintaining the status quo than actually continuing the spirit of the hobby. There is nothing experimental or ground breaking about talking to someone states away using an HF transceiver that cost $4k in analog FM. That stopped being innovative 80 years ago. There are a lot of interesting things being done with RF that are off limits to amateurs because they require a business license.

But you are talking about normal people using radio for normal conversations. That's a distinct use case. Its something worth discussing, the FCC has lagged behind there too but its not the same thing as Ham.

> But you are talking about normal people using radio for normal conversations.

> What it actually gets used for is Boomers chewing the fat

I'm only one data point, but I doubt my generation would 'chew the fat' on a call that anyone else in a wide radius would be listening in on. Not, at least, about anything that's personal. That's the point of my postcard analogy.

Have you never heard of twitter?

>and LARPing as emergency services dispatchers

Uh, they might LARP in your neck of the woods but my county HEAVILY relies on amateur operators for weather related emergencies all year long (tornado country plus snow country).

It's the primary reason my wife and I are getting into amateur radio.

> IMO that's a great way to set up a sandbox: it has built in crowd control and a mechanism to keep out flagrant abuse.

Sadly nothing is really stopping anyone from buying radios online and transmitting garbage. Sure the FCC will come knocking if someone flagrantly transmits without regard for others.

Then again, there are people who police themselves and others. Here's an interesting story about an investigation into a camouflaged jammer:

https://www.youtube.com/watch?v=wZjInmHsWdM

HFDF used to be difficult for the military. Now it's easy for hobbyists. Times change. Rules need to keep up.

I don't mean "chase a squealer with a truck and a dimensional antenna," either, I mean persistent always-on infrastructure to plot emissions on a map. That's a hobby thing now.

Don't scale to the moon, but with a full license you can put out enough power to bounce a signal off the moon...

Getting a technicians license is probably easier than you think. I've heard of amateur radio clubs putting on all Saturday classes with people taking the test at the end. VHF radios aren't expensive, in fact they're importing some from China that are dirt cheap.

Course if you want to work on the HF bands then it requires a bit more work to get the higher class licenses.

This is a pro... learn some radio stuff, pay a tiny amount of money, and get a licence to communicate without the need for random providers.

It's easy though. You can memorize the Technician pool in 5-10 hours with https://www.hamstudy.org or their app - the app is GREAT - (I know, my wife and I just did it and are testing for the tech Saturday, I've passed the last 100 something practice tests in a row) and the General is only slightly harder.

I'm working 60-70 hours a week, plus class, plus church responsibilities and I'm consistently getting 70-71% correct on the General already just from using the app for a half hour or so a day and listening to the question pool via KB6NU's book while I work since Monday morning. I probably won't get up to passing it Saturday but I can just do an online test in the next few weeks once my Tech is in the database Monday or Tuesday.

Getting the General gives you plenty of room to do stuff like this.

I'm gonna be a little bit of a jerk, here. The general can be crammed for but I don't think it should be. Cram the technician license if you just "gotta get on air". The general and extra should be reserved for people who can answer questions at their level and below. Merely reading part 97 of the FCC regulations is enough to technically pass the parts of all three that don't have anything to do with "a station", yet 90% of every argument I've had with hams is interpretation of said rules ( and part 95, and part 90.)

I don't want to discourage anyone, but the investment in effort and money between tech and general is in the 4-5 digit range of dollars and hours.

By all means study. But cramming the test questions isn't studying and will leave you as an appliance operator that will constantly be told, if ever on the air, that they're doing something either rude, against the rules, or dangerous.

I don't feel that any of the questions on the general actually equip me to know how to even connect the components of a complete radio setup up, so I'll just have to agree to disagree.

A good chunk of the questions are memorizing frequencies and wattages you're allowed to use for various things... something you can print off on a chart and tape to the wall.

there's questions about common mode interference and other RFI things, cabling, antennas, and things like that. strict "rules only" is technician - what bands, how much power (which gets interesting in quite a few bands), and so on. Technician is like "set up a modem to get on a BBS."

I assume you're referring to the rule prohibiting "messages encoded for the purpose of obscuring their meaning" (e.x. encryption).

I don't think it's particularly limiting, as you can still use cryptography for purposes other than "obscuring [the message's] meaning", e.x. authentication. You just can't encrypt the payload.

It's also likely necessary to prevent the bands from being overrun with people using them for commercial purposes.

Encryption is a nerd sniping/clickbait topic. I would argue there are other rules with worse impact:

- Baud rate vs symbol rate vs bandwidth occupied

- No spread spectrum south of ~2.4GHz

- New protocols/modes are a catch-22 of needing to be well known to be legal but then how do you create a new one from scratch?

- Use-case specific power limits, like radio control.

- "Gotcha" technicality fines like incidental broadcasting of music or "fleeting" curse words. Intent and pattern of behavior isn't considered.

The symbol rate vs bandwidth is hopefully changing; the ARRL is petitioning the FCC to make it a bandwidth limit instead. On many HF bands, there is limited bandwidth anyways, so the proposed 2.8kHz is a good balance without letting a single individual consume an entire band (i.e. 30m).

Spread spectrum usually requires significant bandwidth, and there just aren't amateur bands below 222MHz that are large enough for that to be truly useful. (The lower limit is 222MHz AFAIK, not 2.4GHz.) Even the 222MHz band is only 3MHz wide, and the largest below that is 4MHz. Spread spectrum starts to make more sense at higher frequencies with 50+MHz bandwidth. If you have examples of SS uses that could work well on the order of kHz instead of MHz, I'd be interested in learning more.

You can absolutely create a new digital mode protocol from scratch. You just need to make the protocol publicly available and let others know what you're doing. You could do a CW or SSB voice transmission before and after each transmission of your custom protocol, explaining where to go to find out more information. (And of course, station identification.) I'd recommend experimenting on some of the wider/shorter-range bands like 70cm first though, and QRP.

This also applies to encryption - if you make the decryption keys publicly available, and you make it clear how others can decrypt what you're transmitting, it is possible to experiment with radio encryption on amateur bands. That goes to the nature of amateur radio - learning and experimentation. But what you can't do is use it for private purposes - there are other bands for that (i.e. ISM). Most of the conversations around this are people frustrated that they can't browse HTTPS sites or have private communications on amateur channels. It would be nearly impossible to ensure people aren't hogging the amateur bands for inappropriate purposes if you can't decrypt/decode what is being transmitted. With such limited bandwidth available, especially on some HF bands as small as 50-100kHz, prohibiting encryption helps ensure equitable access for everyone. It's like complaining about not being able to drive a non-street-legal vehicle on highways. You can still take that vehicle to off-road tracks if you wish and have fun.

Power limits - I don't know what to say on this one, other than if you have a good case for exceeding them for a specific use, contact the ARRL or your regional radio organization. Drum up support in the community. If there's enough interest and justification, rules can change. But QRP is sometimes a fun challenge too.

As for fines, I have not heard of fines being issued as "gotchas" or for minor infractions. Do you have examples? Most of what I've seen are people causing blatant intentional interference or flagrantly violating the rules with inappropriate behavior, repeatedly after several warnings.

Great write up. Took the words out of my mouth.

I'm not sure about the FCC, but usually, only encryption is prohibited.

Otherwise, there are many data protocols, even new ones developed for ham networks, in ~10mbit range for IP, eg:

http://lea.hamradio.si/~s53mv/nbp/nbp.html

Thanks this protocol is very interesting. Hadn't heard of it yet.

Same guy also build his own gps receiver from scratch(!) in 1991(!)

http://lea.hamradio.si/~s53mv/navsats/theory.html

Only a small portion of the worlds Hams are subject to the FCC. Digital experimentation is wide open and active here.

"Texting via APRS has been a thing for about 20 years."

Yes, that's true.

If, by "texting", you mean either:

- A handheld radio attached to a laptop with a serial cable.

- One of two (three ?) models ever produced that allowed you to key in APRS with T9 typing on a number pad.

Yep, it's awesome.

Nailed it. It wasn’t and still isn’t useful or interesting because of the technical overhead of APRS reporting.

Much prefer delving into the weak signal modes. JS8Call is interesting http://js8call.com/

I wanted to write an iOS version of it. Just an iPad and a radio using the audio interface and you’re there. But I don’t have the time to do it.

> If, by "texting", you mean either a handheld radio attached to a laptop with a serial cable, or one of two (three ?) models ever produced that allowed you to key in APRS with T9 typing...

Actually, you can do a good amount of digital modes radio stuff using nothing more than a radio and a smartphone. For example, I myself have made a lot of contacts with people using PSK31 without a cable, using my iPhone speaker and mic near the radio handset.

Digging into how these digital modes work is interesting intellectually. It's doable to implement the signal processing to implement these modes in code. And once you have one mode well-understood, it's also doable to come up with ideas on how to improve upon them and make new modes. Lots of HN readers would be able to do both of those things, and probably enjoy it.

("Modes" here means a way to communicate information over the radio.

https://en.wikipedia.org/wiki/List_of_amateur_radio_modes )

I've sent an SMS over the APRS gateway using nothing but a cheap handheld radio and the APRSdroid app. The app can emit audible data chirps, so you just compose your APRS message, hold your phone near the radio, and push the PTT button. Not very practical, but there's no custom hardware or connector required!

And texting over AX.25 packet radio was a thing before that :) We used to have whole conversations on the local BBS and sometimes even in UI broadcast frames watched in the Rx monitor. Repeated a few times to compensate for loss of course.

After all APRS is just a protocol atop AX.25.

To be honest I never saw the fun in APRS. I don't want to broadcast my position all the time. And that's really all its used for, save the occasional 1:1 text message.

When APRS became popular it took the whole packet group chat thing away. That was a bit like IRC. The old packet radio had much more to offer. It was amazing because the internet wasn't available to us at that time and BBSes required phone calls by the minute. Being online all day would cost more than a monthly wage. But I could be online and chat on packet all day for free.

But because its speed never continued scaling up, it was just too slow for anything but APRS in the end. It's sad that this whole community has gone. I kinda hoped the Digi modes would bring something back but it's mainly just voice. International group voice which is in itself amazing but I miss the chats.

Why use a complete radio when there are cheap modules that could be enclosed along with the logic and screen?

https://www.ebay.com/itm/112889227124

Data sheet here: http://www.dorji.com/docs/data/DRA818U.pdf

Just remember to add an antenna output filter: those modules emit all sorts of harmonics (just like many cheap handhelds such as Baofengs etc).

A 2-way pager! That's so retro.[1]

[1] https://youtu.be/E_nGZ36M0Qo

Perfect for HFT.

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