I noticed another news story from Outernet and I have some comments.
For those who don't know Outernet is a "commercial" /for the greater good, satellite downlink only service providing low bandwidth data, aimed at filling and updating a hard drive with news and info, aimed at developing nations, a free to receive data stream, for educational purposes etc. Their latest stunt/change is to downlink on 12Ghz from a Geostationary satellite, with reception without using a satellite dish, but instead just a bare LNB pointed in the direction of the geostationary satellite, using the gain of the horn inside the LNB.
News stories here: https://hackaday.com/2018/02/22/at-71572-km-you-wont-beat-this-lora-record/
I would hesitate to recommend this system, as it is vapour-ware at the moment, and all the previous kits/hardware released have been dropped and made obsolete by changes to the broadcast. Previous broadcasts were 12Ghz geostationary, but decoded using a DVB-S tuner demodulator, then they changed to L-band low earth orbit immarsat and now they are back on geostationary, this time with a new modulation scheme making pointing easier. They are using the "LoRa" standard, basically just using a protocol that allows low signal margin decoding ( Chirp Spread Spectrum modulation (CSS) which trades data rate for sensitivity within a fixed channel bandwidth. ), similar to WSJT/PSK31 and other low data rate weak signal modes.
It is interesting they thing that a bare LNB (about 80 degree beam width) that seems to be doing the trick, although they also show pictures of patch antennas which presumably are designed for narrower beam width more suited to this.
The main caution I would have is they seem to be constantly peddling hardware, which soon becomes obsolete, without in fact any real business model to fund the venture. They claim their business model will be advertising or donations, obtained after the system catches on, on a large scale, but I have not seen any real attempt to get wide scale adoption in poor regions. They either do not have the funds or cannot get critical adoption for this one-way solution. Anyway I would encourage Amateurs to look at the "technology demonstration" they have made and consider if similar techniques could be applied to LEO or Geostationary Amateur or Emergency uses. Assuming they are still relaying the weekly AMSAT news (I have not seen any actual listing of what is actually downlinked, except for vague references to tests and some of Wikipedia) it might be a good fun project, but beware the technology is very untested and if (or when) they go bust, then the signals will stop. I have to wonder if the L-band service was a short term contract, that they can no longer pay for, and that they have fallen back to cheaper geostationary data.
If someone could set up a receiver (when they actually re-launch/start a new service) and list what is actually down linked, that would be good to know, but for now I would consider it still very much in the testing phase.
I would have thought if they were serious they would have launched a finished tested solution by now, aimed at developing nations and have it backed by advertising to make broadcasting self funding.
On 24/10/2016, Robert Bruninga [email protected] wrote:
The Outernet L-band feed is now carrying a condensed version of the AMSAT and ARISS weekly news files. (Global Geosat coverage except for Northern Alaska)...
Receivers are simple: http://aprs.org/outnet.html
For ARISS, I manually added a 2 char grid square to each school listed in the school schedule and am asking the outernet folks to parse out that location info and plot a 1200 km footprint on their weather globe showing where people can tune in the ARISS contacts. Then their RTL-SDR dongle could then actually be retuned to hear the contact. Just an idea...
-----Original Message----- From: AMSAT-BB [mailto:[email protected]] On Behalf Of Dani EA4GPZ Sent: Saturday, October 15, 2016 7:36 AM To: [email protected] Subject: Re: [amsat-bb] New Outernet L-Band service...
I hope someday a service like this will be available from an AMSAT geostationary service.
I'm pretty confident that the guys at AMSAT-DL are capable of doing this much better on the upcoming EsHail'2 than what Outernet is currently doing on Inmarsat...
They already have in mind a "DVB-S beacon"... broadcast from the ground station at Qatar ... carrying videos about Ham radio and Ham radio events on this signal.
What is more, if you have equipment to operate EsHail'2 on SSB, it's more or less easy to use either the narrowband transponder or the wideband transponder to transmit an Outernet-type signal through EsHail'2, so anyone can have a go with this.
Outernet uses 4200baud BPSK and half of the bitrate is spent for FEC. You can use a bit less bitrate to get a signal that will even pass through a conventional 2.7kHz SSB filter and you can use less bits for FEC to get increased data throughput (but more SNR required).
Sent via [email protected]. AMSAT-NA makes this open forum available to all interested persons worldwide without requiring membership. Opinions expressed are solely those of the author, and do not reflect the official views of AMSAT-NA. Not an AMSAT-NA member? Join now to support the amateur satellite program! Subscription settings: http://www.amsat.org/mailman/listinfo/amsat-bb