Show HN: Sending and Receiving SMS via APRS (VHF Amateur Radio) (opens in new tab)

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.

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.

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").

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.

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

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.

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

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

https://aprs.fi/

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. :-)

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.

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

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.