[freehunter]

I've been trying to solve an issue similar to what Beartooth is doing, and 2 miles is amazing range. Bear in mind, these aren't huge towers hundreds of feet above the ground with 50kWh power sources and million dollar price tags, they're battery-powered, handheld, and consumer-priced. And cell towers with all the advantages listed only travel less than 20 miles. 2 miles with those limitations is a great distance.

I think maybe you're looking at the wrong use case. This doesn't replace GSM, it replaces walkie-talkies (or rather updates it for the text-based world). The use case is you and your friends are at an event downtown and cell service goes out (like it does when the sites are oversubscribed). You're camping and there's no service that far in the woods. You're in a disaster and trying to find your loved ones. It's short range communications, not long-distance calling.

Ham radio would go farther, but sending encrypted communications over ham radio is illegal, so that's right out. This is the next best thing.

[sbierwagen]

  2 miles is amazing range. Bear in mind, these aren't 
  huge towers hundreds of feet above the ground with 
  50kWh power sources and million dollar price tags, 
  they're battery-powered, handheld, and consumer-priced

This guy did 7,600Km at 10mW on the 30m band, using a raspberry pi and a couple passives: https://gerolfziegenhain.wordpress.com/2013/04/13/raspi-as-w...

Of course, the antenna was 44 feet long, and he was transmitting at 1.46 baud, using WSPR: https://en.wikipedia.org/wiki/WSPR_%28amateur_radio_software...

As Shannon proved in the 40s, you can get great range if you can sacrifice bandwidth: https://en.wikipedia.org/wiki/Noisy-channel_coding_theorem

[makomk]

It's true that you don't need much power if both parties have ham radio licences, 44 foot wide antennas hoisted 30 foot into the air, and are willing to transmit unencrypted and very slowly. License-free handheld consumer gear is basically limited to UHF, which is pretty much line-of-sight.

[freehunter]

I mean, using a 44 ft long antenna is kind of what I was talking about. This thing has zero external antenna.

[seanp2k2]

Ham can do text and digital voice over e.g. D-STAR. https://en.m.wikipedia.org/wiki/List_of_amateur_radio_modes

Encryption to obscure your communication is technically against the rules, but things like D-STAR need a proprietary decoder (the spec isn't open) to be decoded, so some people consider that encryption even though it's pretty popular and not being shut down: http://www.amateurradio.com/encryption-is-already-legal-its-...

[tjohns]

D-STAR is actually an open standard.

The only part that's closed is the voice codec (AMBE). But if you just want to transmit or decode data packets, you can definitely build your own hardware. There's even a couple SDR modules for it:

http://www.flexradio.com/amateur-products/flex-6000-signatur...

http://www.rtl-sdr.com/listening-d-star-digital-voice-dsd-1-...

[HeyLaughingBoy]

...or you're on a small farm that's half a mile on each side and you need to know that the gate on the opposite corner from the farmhouse is still closed.

A minor change of perspective and suddenly a 2 mile range is fantastic!

[chipperyman573]

>Ham radio would go farther, but sending encrypted communications over ham radio is illegal, so that's right out. This is the next best thing.

How come? I don't know much about ham, but it doesn't seem like it'd make much sense to make it illegal.

[lfowles]

Ham radio spectrum is strictly for non-commercial use. If encrypted communications were allowed, it would be a lot easier to sidestep that with plausible deniability.

[zubeen]

What frequencies are they using (sub 1ghz with audio) ? is 2 miles really possible ?