L Band Do-It-Yourself (DIY) Receiver

#1

We have all had good luck building the DIY ORxPi receivers operating over geosynchronous Ku Band satellites. Of course, not without some glitches :hushed:

Now, with L Band potentials being worked by Outernet, I think it would be a good idea to collect L Band work in one spot.

Questions to addressed would be how modify the ORxPi for L Band, how to make a Lighthouse work in L band, etc. I would also suggest we leave out the Lantern receiver since none of us have one yet.

Please add your ideas here. Thanks, Ken

#2

Ken this is a great idea putting all L-Band ideas in one3 spot.

My L-Band interest would be a L-Band Antenna for a moving vehicle if such a thing is possible.

I would also appreciate if the people with Industry experience could take the Time to use all the Correct abbreviations and terms so I can start to learn L-Band terminology.

George

#3

Ken can you define the L-Band experience.

What will the footprint look like?
What will the data rate be?
What size antennas will we need?
Can RTL-sdr realtek usb dongle work with a “UP” converter or will we need different hardware?

#4

The receiver,s picture is here:
https://github.com/Outernet-Project/RTL-LNB/blob/master/LNB.jpg

#5

Will Outernet be selling these as a kit?
Any idea on Price.

My summation is it will receive

L-Band 10 MB a day mobile Outernet service with small patch antenna…

Ku, C Band service …1 GB a day fixed large dish service.

#6

Probably so as you say

But, what can we do now with our Raspberry Pi ORxPi devices to receive an L Band signal when Outernet starts to broadcast one? I’m thinking we add some appropriate software defined dongle type receiver with an appropriate L Band antenna and create an LORxPi :yum:

Hopefully, we can add the same dongle/antenna to a Lighthouse and do L Band downloads there too.

Rather than beating the ORxPi/Lighthouse to death in Ku Band, we start working it over in :wink: L Band. Ken

#7

Can we use L band to Ku band converter to mapping the signal? Just an idea :slight_smile:

#8

The goal is to definitely offer an L-band version of ORxPi, but there is a serious bit of work that needs to take place before that can happen. You’ll note that in ORxPi there is one closed source binary blob. This is a piece of code that turns the DVB-S2 stream into files. For L-band, the modulation scheme is highly proprietary (not by our choice; it belongs to ViaSat) and so they need to release a software-based demodulator. Once we have that, then we can use general processing power to demodulate and decode the content that is delivered over L-band.

They have already done a comprehensive engineering study and they peg the project to take 6 months. ORxPi-L will be awesome, as it will only require a 4-inch antenna. But we may be jumping the gun a bit, because the software to make it run won’t be available for a little while.

#9

Syed, when Outernet is ready to suggest a method for DIYers to tinker, please post a note - - pin it!

In the mean time, we will continue our efforts with the ORxPi and Lighthouse. Ken

#10

Syed does this mean the Lantern hardware release will be effected by this same issue?

If you have solved this issue for lantern why cant we use that solution with the Linux Vesion of Outernet Rx which could on a powerful pc have plenty of decoding grunt.

George

#11

Actually, the new Lantern handles demodulation with an FPGA and DSP. The goal of the software demodulation project is to move all of that processing into a PC. The engineering review showed that an Intel i3 should be able to do the job.

#12

This Blog has a lot of Info On Outernet L-Band.

http://www.rowetel.com/blog/?p=4538

2 Likes
#13

Here is a picture of the proposed Outernet L-Band patch antenna from David Rowe’s Blog.

#14

http://blog.outernet.is/update-on-lantern-hardware/

This Blog has a picture of the improved L-Band SDR Dongle receiver.

#15

That’s actually old information now. This is prior to us signing the ViaSat relationship. The antenna is still usable, but we’ll need to use ViaSat’s waveform. We could always lease our own bandwidth and install our own modulator, but that adds considerable cost to the equation.

#16

Thanks Syed,

Is ViaSat’s waveform propriatry or Open Source?

What are the charactoristics of ViaSat’s waveform and what is the benefit of signing with them>

#17

ViaSat’s waveform is proprietary. The benefit of working with them is leveraging their engineering efforts, as it relates to hardware development–especially much lower cost satellite terminals that they have in their roadmap. We also benefit from their experience in developing network hubs. If we were to limit ourselves to just a broadcast service, this is something we could/can do ourselves. But adding in even a tiny return link significantly complicates things. And lastly, there was also the matter of dollars and sense. Satellite bandwidth is the most expensive line item in our budget.

#18

Thanks Syed.

I think the Viasat relationship raises a couple of Open-source and Community vs Propriety issues.

Will we still be able to “Copy Outernet Technology” and build our own “DIY L-Band Receiver.” Even though Viasat is propriety technology.

Will Outernet be selling L-Band OrX kits like it did Lighthouse kits? Any idea on pricing.

What kind of Antenna does Viasat technology use?

Also is Outernet proposing a possible future return path on L-Band satellites.

George

#19

Has any one tried decoding Inmarsat L-Band frequencies as per the tutorial below. These frequencies will be very very close to Outernet’s future frequencies and also GPS frequencies. Hence you can use a old GPS antenna possibly. Any antenna you build could also work with Outernet L-Band offering.

http://www.rtl-sdr.com/rtl-sdr-tutorial-decoding-inmarsat-std-c-egc-messages/

I have a Circular UHF TV antenna with 15 meters of 75ohm coax that I have connected a RTL dongle with the highly sensitive e4000 (Elonics tuner no longer available). This plugs into my Ubuntu Linux I7 Laptop. I run Andy 18 Ham radio 64 Bit Ubuntu virtual disk in Virtualbox as for some reason the RTL dongle crashes in 32 bit Ubuntu.
I can get the Windows Inmarsat decoding software and the Java decoding software to go into sync mode when monitoring Inmarsat L-Band frequencies. But I cannot get it to receive text safety and Navigation warnings from Inmarsat.

I am unable to be certain that I am connecting to the Correct NCS transponder on the Inmarsat 4-F1 Satellite that is above the Philippines. Does any one know the NCS frequencies that can be publicly monitored on the Inmarsat satellites?

80%Quality Inmarsat 1545.59721:47.png1366×768 288 KB

#20

Thanks @Seasalt, This is very interesting.
I think we can use the Java based decoder at http://www.tekmanoid.com/egc.shtml

I’d like to test this but it will take some time. :smile:

@Syed, what you think about this?

Pasted image720×516 292 KB