Show HN: Sending and Receiving SMS via APRS (VHF Amateur Radio) | Hacker News Reader

Show HN: Sending and Receiving SMS via APRS (VHF Amateur Radio)

smsgte.org

134 pointsjlturner44 comments

All these messages are of course completely public, and you can even get a full history of people using this service here:

https://aprs.fi/?c=message&limit=50&call=SMSGTE

Very cool stuff.

Because it’s a legal requirement to not encrypt the message?

Legal requirement to not encrypt any Amateur Radio transmissions, yes.

Not actually enforced, and in some cases Amateur Radio transmissions are actually required to be encrypted:

https://www.amateurradio.com/encryption-is-already-legal-its...

If you have enough money you can build a system that is technically encrypted. See Fusion, d-star, and the other one I can't remember.

What the FCC doesn't want is message passing that is not decryptable by them. They could care less if me or you can't decrypt fusion with an sdr.

An interesting grey area is pactor. And not just for encryption, but also "symbol rate". If anything is going to bring ham radio into this century kicking and screaming it is stuff like aprs and pactor; and I say that knowing how awesome JT and wspr are.

No. Neither fusion, dstar, nor DMR use encryption. They are all publicly published modes.

This has to be one of the most practical applications of amateur radio. Keep in mind that all of these comms are unencrypted and are visible by anyone who has the ability to receive.

SMS (especially traditional GSM SMS) is often unencrypted or poorly encrypted and visible by anyone.

Yeah, but that was considered a problem and subsequently fixed.

Can't fix that in the context of HAM radio

And "the ability to receive" means "has a browser and internet access".

https://aprs.fi/

These are visible not just by anyone who can receive, but pretty much everything on APRS ends up online. Most areas have an igate that forwards messages from the radio to the Internet. https://www.aprsdirect.com/center/40.55354,-104.97842/zoom/1... is my favorite site for seeing what is going on in an area and where digipeaters and igates are. https://aprs.fi also works.

Some areas have one that works in reverse, taking what is seen on the internet and relevant to the active stations in the area and broadcasting it out over radio.

When I started using SMSGTE I had great success getting a SMS from my radio to a phone, but only 1 in 10 replies from SMS made it back to my radio. I put up a gateway for my area and so we have some decent bi-directional coverage.

Hold up, does that mean you are allowed to transmit on SMS/GSM/?? frequencies with a "end user/private operator" type license? Or do you have to fiddle with your phone to get it to listen to an alternative band? (As is probably obvious I have no experience with radio)

Not exactly, you transmit on a “normal” VHF frequency (which you must be a licensed amateur to broadcast on) and the data gets picked up by a “digipeter” (radio to internet repeater) which then gets picked up and relayed to SMS by a gateway (a server looking for messages to send). This infrastructure exists and only requires a license, radio, and APRS interface (probably your iPhone/ Android device).

Where would I find out how to set up bidirectional APRS for our local club?

Google “APRS digipeter setup”, you’ll find lots of solutions which fit your needs (mobile, home station, etc).

This video explains a raspberry pi setup with Dire Wolf (software TNC): https://m.youtube.com/watch?v=YqTpyPLtjUA

thanks! direwolf comes up often in those searches.

I used this because my hardware list was similar. https://www.foodstoragenow.com/non-food_essentials/communica...

Aprx works for me, Direwolf seems pretty popular. There are many different ways.

I'll look into it, thanks!

Also supports optional message ack by placing ? after callsign. I’m looking to use this in the woods in case of emergency as you can forward your APRS message through one of the many digipeters available on mountain tops. Interested to hear of anyone has given this a try yet!

It supports an ACK, but unless you have a two-way i-gate nearby you should probably consider it to be a one-way protocol. All of the ones near me just go RF -> internet so there's no way to get a response back to RF unless you're running your own.

Still useful for sending out quick status updates like "I'm doing fine but running late" but not good for full blown communication.

Exactly this. My wife knows not to panic if she can get my messages, but I don't reply to her. If any hams live in an area w/o a two-way i-gate, consider putting one up. It isn't that hard and provides a nice service.

It does work! I have called for help in a non-life threatening situation with no cell service by using APRS to SMSGTE while doing some off-roading. Even better, you don't even have to have a digipeater nearby. About once every 1.5 hours you can get a chance to send the packet via the ISS during a pass. SMS via space. :-)

Holy shit game changer. Finally time to dust off that ham license. Any tips on how to setup this ? Ideally I want a cheap handheld system I can send apfrs messages.

Yeah you can use a cheap Baofeng radio (can get as low as $15-20), an “APRS cable” for it (about $20 on Amazon or make your own) which takes mic/ptt and audio out and feeds it to a 3.5” TRRS plug (think iOS / android headphones with mic plug), and an APRS app on your phone.

Radio -> cable -> cellphone audio jack -> APRS app

If you have an iOS device probably using a lightning / usb-c to 3.5” TRRS jack too.

Wow, do you have a parts list on that cheap radio and APRS cable?

I’m using a Baofeng UV-5R (radio) and the APRS-K1 cable. I’ve linked Amazon pages but you can get them for slightly cheaper off eBay or AliExpress.

Radio: https://www.amazon.com/Baofeng-UV-5R-136-174-400-480Mhz-1800... Cable: https://www.amazon.com/BTECH-APRS-K1-Interface-APRSDroid-Com...

"Radio -> cable -> cellphone audio jack -> APRS app"

While this works, it is just the start. Soon you realize that you want to actually use your phone AND APRS at the same time and that your audio and mic are busy. I did this for about a day before seeking out something better.

Radio -> cable -> Mobilinkd Bluetooth TNC paired to your phone -> APRS app

Now you can take calls, play music in the car and drive down the road with a radio paired and use APRS. This isn't a bad setup, the big pro us the multitasking and using the APRS app on your phone to write messages.

The other way I've done this is a radio that has the TNC and APRS built in. A handheld like the Kenwood TH-D74 can send and receive messages without any additional hardware, but you have to write the messages on a lame keypad like in the dumb phone days. I like this for backpacking as there are fewer pieces to worry about.

It is fun stuff, and can be a life saver. Check out https://hamstudy.org/ the easiest level (Tech.) is enough to get you access to all of this.

Yep totally right. Worth noting that you can use an older phone repurposed for connecting to a cheap baofeng for just APRS purposes. Radios with APRS are great but quite expensive.

Also 100% recommend anyone interested getting their Amateur Radio Technician license. TBH you can pass the test with an afternoon of study, and the advanced licenses are really only needed for additional HF spectrum privileges.

I'm starting to see a lot more interest in shortwave radio and radio in general recently. Is it just me being out of the loop or is anyone else noticing this?

Maybe it has to do with the start of solar cycle 25? Expect to see improving HF propagation over the next 3-5 years. It's an exciting time for radio nerds.

I've read that we're at sar minima until the most 2040s, so I'm not holding my breath for better propagation anytime soon.

Bit of a nitpick, but the standard APRS frequency in North America is 144.390MHz, well above the "shortwave" bands (granted, it's still "radio in general").

Yeah... I hear shortwave and amateur radio (aka ham radio) used interchangeably all the time - but it isn't correct.

a lot of folks (me included) have no idea what the differences are :)

Shortwave refers to a band of frequencies with particular characteristics. Ham refers to radio bands allocated to amateur radio. There are shortwave frequencies that hams can’t operate on and there are frequencies outside of shortwave that amateurs can operate on.

"Shortwave" just refers to a range of frequencies (which, counter intuitively, are on the longer end of the wavelength spectrum). It's generally used to refer to the 3-30 MHz range.

Ham (amateur) radio is a pretty wide range of radio activities performed by folks who have passed an exam and received a license to transmit using various modes on various frequencies (there are a few different licensing levels that grant different privileges). Activities include everything from talking to other hams in your local area using a VHF/UHF handheld radio (often via a repeater), to long range voice or "morse code" communication over hundreds (or thousands) of miles using the "shortwave" bands, to very long range (and very low bandwidth) modes like FT8 (Ever wanted to send 12 bytes to someone on the other side of the world? With FT8, you can!)

Data on shortwave is really cool. You can get super long distances bouncing off the ionosphere or even meteor scatter trails.

My speculation is that being surrounded by ubiquitous wireless technologies, some people are going to be curious about the nuts and bolts of it all and want to understand how it works. A second factor is that things like RTL-SDR that allow exploring interesting signals for about the cost of two decent burritos makes it very low friction to get started. I hope the interest continues to grow.

Might be because there is now inexpensive gear available, eg Baofeng?

SDR. Easy to interface radios with computers so like every other thing you hook computers up to, it rockets the state of the art forward.

APRS is cool, but it’s also somewhat… complex. I wonder how hard it would be to write a “modem chat” phone app, with the ability to translate text into audible Bell beeps, slow enough to work without cables, to be used over ordinary voice frequencies.

There are apps that decode via phone microphone, most of the stuff that fldigi and radios can do out of the box (for example, rtty)

It works well, and is bi directional, you can key a transmitter and hold its microphone to your phone speaker and transmit valid "digital" modes.

Works fine, especially over repeaters, which annoys the old folks and the lids alike.

Look up PSK31, RTTY.

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