GoTenna – Send and receive messages even when you don’t have service • Hacker News Board

Re: GoTenna – Send and receive messages even when you don’t have service

#151

Post by TD-Linux » Sat, Jul 19, 2014, 6:06 PM UTC

glomek wrote: post #116

daniper wrote: post #84

Earlier quoted context omitted.

We want to do that, but FCC regulations don't enable meshing (currently) on the bands we're using (151-154 MHz, aka the MURS band). We considered releasing a 900 MHz device that the FCC allows to mesh but then you only get, if you're lucky, up to 0.5 km range and it has to be line-of-sight. So we went with MURS because you can get greater range and don't have to be line-of-sight; the propagation characteristics are b…

Do you intend to release the specifications for the protocol you are using? For example, would I be able to hook a computer with gnuradio up to a MURS radio and write software that could communicate with a goTenna?

This. I am super excited about the GoTenna because it is basically Ham Radio for the masses. But I'd also like to talk to GoTenna users with SDR or similar - in the spririt of non-encrypted ham communication.

Re: GoTenna – Send and receive messages even when you don’t have service

#152

Post by TD-Linux » Sat, Jul 19, 2014, 6:07 PM UTC

spiritplumber wrote: post #148

So my guess is, it's a bluetooth radio and a XBee. Nice? I think? What surprises me is the size of it; I've deployed exactly this (minus the spiffy packaging, admittedly) for barge tracking applications since 2008, and the whole thing ended up being roughly the size of an early 2000s palmtop computer, so good job on that! The schematic is trivial: a xbee XSC (we used XStreams at the time) with a decent antenna couple…

No. It is in the 150MHz (VHF) range, which is probably one reason why it is as long as it is. I assume they rolled at least a semi-custom radio solution.

Re: GoTenna – Send and receive messages even when you don’t have service

#153

Post by GrinningFool » Sat, Jul 19, 2014, 6:07 PM UTC

Offtopic:

Yet another site that uses a ton of scrolling, space, and images to provide information that would fit in a couple of paragraphs. It's true that a picture can speak a thousand words. On the other hand a few dozen words can make up for six giant pictures that convey little information.

Note to mention the giant video that greets me. Has this actually proven effective, as it becomes more and more common? I don't know about most, but I will seldom watch a product video during my day - I don't have time or patience to wait for speed-of-speech delivery of information.

Re: GoTenna – Send and receive messages even when you don’t have service

#154

Post by TD-Linux » Sat, Jul 19, 2014, 6:12 PM UTC

meatmanek wrote: post #129

sbierwagen wrote: post #107

Earlier quoted context omitted.

CFR 2009 § 95.1311 MURS stations are prohibited from operating as a repeater station or as a signal booster. This prohibition in- cludes store-and-forward packet oper- ation. http://www.gpo.gov/fdsys/pkg/CFR-2009-title47-vol5/pdf/CFR-2... Pretty clear cut. No packet routing, at all, for any reason, using any method. Doesn't matter if the radio firmware is doing it or if the client is doing it. (There is a general exe…

I wonder whether the FCC is going to consider Bluetooth MURS interconnection to be in violation of this rule.

Bluetooth is a short range encrypted point to point link. It would be considered part of the station. Repeaters, in radio jargon, generally accept input from many sources, often without access control.

Re: GoTenna – Send and receive messages even when you don’t have service

#155

Post by peaton » Sat, Jul 19, 2014, 7:06 PM UTC

njloof wrote: post #147

peaton wrote: post #141

Earlier quoted context omitted.

I mean, I know it's not secure. But I had no clue it was down-vote-not-secure!

They're not downvoting you because it's not secure; they're downvoting you because you don't understand what the product does.

Then you misunderstood, or I am perpetually misunderstanding. The comment that I responded to asked for a way to use this product to send actual text messages. He wanted to relay a message to another phone via this product and then have his phone send an actual text message using information from the initial message. I gave a suggestion about how to do that.

Re: GoTenna – Send and receive messages even when you don’t have service

#156

Post by daniper » Sat, Jul 19, 2014, 7:37 PM UTC

TD-Linux wrote: post #150

ryanmarsh wrote: post #145

Say you are just 1 mile from a friend, at 151Mhz the fresnel zone is 72ft tall. If you are both at equal elevation on flat land then 50% of the signal is going to be absorbed by the ground. How exactly does this scenario work? Source: I used to build outdoor medium distance (~1mi) wireless data networks with 900Mhz and at 1 mi the fresnel zone is roughly 30ft tall so we would put our antenna 20ft in the air. The awes…

The propagation characteristics of VHF are substantially better than 900MHz. I've used voice radios in the VHF band in urban Minneapolis, and have been able to easily surpass a mile of range. I'm surprised they didn't choose a lower frequency still. In addition, using something like DSSS, a low data rate, and retransmission ability will probably help a lot for this application.

Agreed. Substantially better. Our first goTenna prototypes worked at 900 MHz band and we could barely get 0.5 km (NOT MILES) line of sight. With the goTennas that are now out for pre-order, we've gotten anywhere from 0.5 miles to 3.5 miles in NYC (where we're based), to give you an idea -- and there's little that is as non-ideal for RF propagation than a metropolitan city.

Re: GoTenna – Send and receive messages even when you don’t have service

#157

Post by daniper » Sat, Jul 19, 2014, 7:38 PM UTC

TD-Linux wrote: post #152

spiritplumber wrote: post #148

So my guess is, it's a bluetooth radio and a XBee. Nice? I think? What surprises me is the size of it; I've deployed exactly this (minus the spiffy packaging, admittedly) for barge tracking applications since 2008, and the whole thing ended up being roughly the size of an early 2000s palmtop computer, so good job on that! The schematic is trivial: a xbee XSC (we used XStreams at the time) with a decent antenna couple…

No. It is in the 150MHz (VHF) range, which is probably one reason why it is as long as it is. I assume they rolled at least a semi-custom radio solution.

Yes, we've built everything from scratch! It's been fun/impossible. :)

Re: GoTenna – Send and receive messages even when you don’t have service

#158

Post by daniper » Sat, Jul 19, 2014, 7:38 PM UTC

glomek wrote: post #116

daniper wrote: post #84

Earlier quoted context omitted.

We want to do that, but FCC regulations don't enable meshing (currently) on the bands we're using (151-154 MHz, aka the MURS band). We considered releasing a 900 MHz device that the FCC allows to mesh but then you only get, if you're lucky, up to 0.5 km range and it has to be line-of-sight. So we went with MURS because you can get greater range and don't have to be line-of-sight; the propagation characteristics are b…

Do you intend to release the specifications for the protocol you are using? For example, would I be able to hook a computer with gnuradio up to a MURS radio and write software that could communicate with a goTenna?

We have an open SDK coming out soon -- you can sign up for developer updates at our website

Re: GoTenna – Send and receive messages even when you don’t have service

#159

Post by daniper » Sat, Jul 19, 2014, 7:39 PM UTC

konstruktor wrote: post #136

andruby wrote: post #133

Earlier quoted context omitted.

What's the rationale of the FCC to disallow this? Purely economic reasons?

I think congestion is the main reason. If a transmission had unlimited range (hypothetically), the band would fill up pretty quickly, so it would stop being useful. Natural limits of signal transmission and power limits are what makes public, unlicensed bands feasible. They limit the possible uses, but, stochastically, enables many people to use it at the same time. At any repeater hop, the transmission uses double t…

Congestion is definitely the main reason. What we've done at goTenna's networking layer though, is we've made it listen-before-talk. That, added to the fact that we're only doing short-burst transmissions, makes it highly unlikely goTenna will ever "step on other tranmissions' feet."

Re: GoTenna – Send and receive messages even when you don’t have service

#160

Post by daniper » Sat, Jul 19, 2014, 7:40 PM UTC

chrisBob wrote: post #32

UweSchmidt wrote: post #17

Earlier quoted context omitted.

For now the chances of finding a third GoTenna user is quite low. In the future though this could be an alternative private Internet. A BitTorrent client could be a hit.

I think you are over estimating the bandwidth involved. They don't state much about the wireless protocol, but I am betting you don't want to send much more than a text message to get that range.

goTenna's transmission rate goes up to 19,200 baud