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back to article GoTenna: How does this 'magic' work?

You may have been hearing about a well-nigh miraculous device called GoTenna lately - a gadget which, apparently, lets your phone work even if there's no network coverage to be had. GoTenna is a two-way radio for mobile phones: it pairs with an Android or iOS device using Bluetooth and uses 151-154 MHz radio to communicate with …

Meh

What's the frequency Kenneth?

I think you might want to note that across the pond (or Pacific), the 151 - 154 MHz block operates as licence free general user spectrum for our cousins. Elsewhere in the world, that block is occupied by licensed services so any Gotenna use outside of the 50 might prove problematic to say the least, you might even get a visit from one of your local spectrum police if you are really lucky

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Coat

Re: a visit from one of your local spectrum police if you are really lucky

Presumably, if you're unlucky, the Mysterons get to you first?

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Re: a visit from one of your local spectrum police if you are really lucky

SIG

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WTF?

If you want line of sight PTT why not just by a VHF transceiver aka walky-talky?

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Pint

Re: WTF?

Then settle for UHF, specifically 'Family Service Radios'. They can also achieve 50+ km range *.

(* No they can't. Not without aircraft or mountains being involved.)

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Anonymous Coward

Re: WTF?

"VHF transceivers require licenses and training?"

PMR433 (as in 433MHz) or maybe 446 kit is unlicenced (no licence needed for operator or equipment), dirt cheap, and available from all fine high street electrical shops for less than £50 for a pair of handsets.

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Re: WTF?

"Because VHF transceivers require licenses and training?"

Not all of them, PBR licence is £60 for 3 years for any number of radios.

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Facepalm

Re: WTF?

Damn, just took the walkie-talkies we used to use on holiday* when the kids were little to a charity shop. I could have been at the cutting edge of physics.

/* These days they probably all have mobiles with a roaming tarif. But 5 or 10 years ago it was a great compromise when they wanted to go off in the resort hotel themselves.

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In fact, goTenna will even work if your smartphone is in “Airplane Mode”! How does this magic work?

It could achieve this by receiving messages and buffering them till the phone bluetooth comes back online

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Enabling flight mode will disable Bluetooth but you can toggle Bluetooth back on, leaving the phone otherwise in flight mode (it's the same for WiFi too). At least on Android anyway.

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not really flight mode then is it :/

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Bad choice for a name too

Tenna ~= Tena... as in Tena Lady?

The part about Cambridgeshire being a mob dead spot made me smile. So often I've been somewhere in Cambridgeshire, thought "I'll just check my... no I won't...".

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Pint

Re: Bad choice for a name too

"Cambridgeshire being a mob dead spot"

Not sure what it means but I'll avoid going there just in case.

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Re: Bad choice for a name too. Yes but how does Tenna Lady work?

My immediate thought was of Tenna Lady and as I'd always wondered how 'one way' fabrics work hoping for an answer!

I remember 'one way' nappy liners 30 years ago when my children were babies and thinking, but they don't tell me which side to put next to the skin?

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Anonymous Coward

Re: Bad choice for a name too

"Not sure what it means but I'll avoid going there just in case."

For reasons of name association that conjured visions of the shop in Royston Vasey**.

**Which was supposed to be set in the Pennines

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Anonymous Coward

Re: Bad choice for a name too

Never been there (in Cambridgeshire), but not having mobile coverage makes it a rather attractive place to be.

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Boffin

"... We are operating at the limits of physics,"...

One wonders if perhaps Ms. Perdomo is operating at the limit of her understanding of physics.

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Re: "... We are operating at the limits of physics,"...

... Professor Wagadogo of the University of Balaloosha grunted.

"Now look at this, youngsters!"

He pulled a tiny square box from his pocket. He pressed on one side of it, and a section of the box slid out, revealing row upon row of minute little sticks each topped with a reddish blob at the end. It was a matchbox. Some of the students in the audience had seen similar ones before, in the 20th century section of the Balaloosha District history museum.

Then Wagadogo pulled one of the matches and struck it against the box. A bright flame appeared at the end of the tiny stick, drawing muffled gasps of amazement from the lecture theatre.

"How does this magic happen? said Wagadogo, pushing away one particularly reckless and annoying student who was about to get his hand burnt. "Don't touch it you id...Brilliant Hope of the New Generation! We are at the very limits of Chemistry!"

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Anonymous Coward

Re: "... We are operating at the limits of physics,"...

Classic Asimov... great reading

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151-154 MHz

Only in USA.

USA FRS and Europe PMR446 are not compatible.

There is no PMR443, In Europe there is SRD433 and SRD864, SRD = Short Range Device, i.e. about 30m range, a few mW for lower power "toy" walkie talkies, video sender reverse remote links, Wireless door bells, wireless Weather sensors etc. Similar short range for 49MHz CE and so called "iTrip" VHF 88-108 FM Stereo transmitters. CB is legal in most of Europe (but not all on same bands/modes) and can be SSB, 4W or 5W, I think. Decent very large Whip aerials are needed for range, but can seriously beat PMR446. But a special new regulation would be needed for Data use like this. You could just talk on a legal licence free CE marked hand held CB (8ft whip is good!) or a PMR446.

This GoTenna is mostly marketing hype. Also in Europe a PMR446 version would need a new derogation from the regulators for text data use. Do-able though. There may be some short range (1km to 5km) application for the idea on Moorland, mountainsides or water where there is no cellular coverage.

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Re: 151-154 MHz

I mean no PMR433, not PMR443 (well that doesn't exist either)

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Anonymous Coward

So it's a proprietary...

...and amateur version of LTE D2D, with fewer capabilities, no standardization, and bugger all chance of finding somebody to communicate with when you really need it?

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*Duncan Bannatyne voice* I'm out

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Sounds like packet radio to me

Sound alike old-skool VHF packet radio with the GoTenna acting as a TNC & BBS. This was being done in 1980. Nothing new here.

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Re: Sounds like packet radio to me

I was just thinking that … Basically a TNC with a Bluetooth interface.

I already have an equivalent that does text messaging on 145.175MHz* with 5W transmit power, just lacking in the Bluetooth connectivity.

(* Australian National 2m APRS frequency.)

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No, point to point only

GoTenna operates under FCC MURS rules, which allow point to point voice or data (rather narrowband, to be sure, by today's standards), but do not permit repeating (the heart of packet radio) or interconnection (to use it to extend cell coverage). So it basically does a little FRS-like thing for your smartphone, for fully off-grid use.

Multi-Use Radio Service, with five channels in the 151-154 land mobile range, is one of the more obscure FCC rules. I've never seen anything else use it.

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Re: No, point to point only

So it's castrated packet radio… even better. A bit like my Garmin Rino then.

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Tetra

Isn't this one of the selling points of the Tetra tech used by the emergency services?

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Re: Tetra

Yes, TETRA does the funky ad-hoc mesh network setup if your handset can't see a base station; but it does voice and data.

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Or without any additional hardware at all

You can add an app to your smart phone that creates an ad-hoc mesh network on the 2.4Ghz ISM band that does the same kind of thing.

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Re: Or without any additional hardware at all

A bit more detail would be welcome.

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Re: Or without any additional hardware at all

Won't work on Android unless you root the phone. Google has disabled ad-hoc WiFi apparently due to pressure from carriers.

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Black Helicopters

Citizens' Band

Perhaps the manufacturers could consider using this? Or did they never watch those anarchic trucking movies of yesteryear?

But maybe the operation of this would be stuffed by sunspots...

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Anonymous Coward

Re: Citizens' Band

Packet radio is legal on CB - has been for years across UK and europe. Radio amateurs have been sending each texts since the 1980's.

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Re: Citizens' Band

Packet is legal on 10m Amateur.

Not on CB 11m in most of Europe. I'm sceptical that Ofcom allows it.

CB != Amateur

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Icom ID-5100 can already do this...

Icom ID-5100 and the icom android app RS-MS1A (snazzy title!) can do exactly the same thing, and more... bit more expensive though for the hardware.

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Text over PMR??

Garmin "Rino" walkie talkies can send txt between each other. They also have built in GPS

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Re: Text over PMR??

"Garmin "Rino" walkie talkies can send txt between each other. They also have built in GPS"

They communicate via FRS, only available (legal) in the US. It tends to clash over other bands in other countries.

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Perhaps the GoTenna could be used standalone?

Some kind of mechanical key switch device could allow the user to send text messages, having first translated them into a sequence of variable length key-presses

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Somewhere without mobile connectivity

"The thought being, if you are somewhere without mobile connectivity – like the wilds of Cambridgeshire" If your with 3 Network that's pretty much most of the UK outside of the major cities.

I don't even get a signal in my office in London. Perhaps its called 3 as three times a year you will get a signal.

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P.T. Barnum validated...

One is born every minute...

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Roll your own

1, *Buy/build (its open source) this bluetooth TNC: http://www.mobilinkd.com/

2, Check this out to your laptop: https://github.com/lulzlabs/AirChat

2a, Or port to java app for your phone if you like.

3, Buy cheap Baofeng UV-5R radio off ebay for £25

4, Keep moving so OFCOM don't catch you in the unlikely event they aren't asleep at the wheel

*You dont actually need the TNC and indeed it probably isnt supported with airchat as is, it just uses the soundcard of a laptop as a modem but using a TNC shouldnt require too much of a change

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Paris Hilton

If your smartphone is in Airplane Mode...

shouldn't your goTenna be in “Airplane Mode” too?

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Free dosh required...

I am designing a new system that let's mobile phones communicate even when there is no wireless signal. The patented signalling device, the FocusLensingAirGewGaw or "flagg", is used in tandem with an app on the mobile that uses the camera to identify a number of error-correcting changes in position of the "flagg". This system operates at the limits of physics and the boundaries of belief. Together with our patented signalling protocol DynamicAirFlaggTilting or "daft", we are able to probably demonstrate on a good day with your cash in our pocket that you will definitely be occupied sending terse, unprintable audible messages until the mobile network is restored or you reach the limit of messages that can be encoded in this way.

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Re: Free dosh required...

it was one of the things the Romans did for us

http://www.nationaltrust.org.uk/document-1355766855655/

You will need:

sheets of A4 card

felt tips or crayons

sticky tape

scissors

garden canes/thin sticks

pens

coded grid keys

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Airplane Mode does not disable BT

Airplane mode on my phone does NOT disable BlueTooth.

Maybe you need to get a new phone?

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