[amsat-bb] Global Geo SATCOM system?

Scott scott23192 at gmail.com
Fri Oct 7 05:28:39 UTC 2016

I have a couple of additional pieces of information to pass along on this
topic as of tonight.

As many are aware, the Outernet hardware "package" consists of a patch
antenna, LNA, and unmarked SDR with bias-T enabled.

Tonight I remembered that some time ago I could not resist buying a couple
of the second (?) generation metal-case RTL-SDR dongles from rtl-sdr.com.
I have been using one on my linux computer but the other one was unused.
Remembering that these rtl-sdr dongles had 5v bias-T as an option, I took
the unused one apart and soldered the appropriate pins to enable the
bias-T.  That allowed me to do a comparison with the unmarked SDR that came
with the other Outernet items.

Setting Outernet aside for a moment, I did an apples to apples comparison
of the L-Band AERO signals coming from Inmarsat 4-F3.  The difference in
signal strength was obvious and substantial.  The rtl-sdr gave me over 10db
more SNR, so in addition to the 600 & 1200 AERO data streams, I could now
easily decode the 10k AERO signals where there is a lot more (and more
interesting) traffic.

So with that test complete and fairly conclusive, I reconnected everything
to the Raspberry Pi but with the rtl-sdr dongle this time.  Not
surprisingly, the L-Band Outernet signal was also greatly improved.  Where
my SNR figure had been around 3, with the rtl-sdr dongle it was varying
between 6 & 8.  Please keep in mind that I do not have a clear sky view, so
take all of these findings with that in mind.

A few minutes after powering up the Pi and seeing the improved SNR figure,
content from the satellite started downloading.  As you might expect, the
rate seemed to be noticeably quicker than before.

Imagine my surprise to see the first file arrive as a .tgz compressed
archive that, when extracted, contained some amateur radio content!  Here
are the first few lines from the file that just arrived:

OUTERNET>APRS:>OUTERNET file created Fri Oct  7 05:00:19 UTC 2016
VI50CC>APRS,RS0ISS*,qAR,ZL4JL-6::RS0ISS   :Hello ZL   James G/day Mate
RS0ISS>CQ,qAS,ZL1KM-H:>ARISS - International Space Station
K6PKL>CQ,RS0ISS*,qAS,KK6RKY:=3748.51N/12112.44W-Solar powered, 20 watts
j-pole {UIV32N}
RS0ISS>CQ,qAS,KK6RKY:>ARISS - International Space Station

... and it continued with similar APRS type traffic.

So, if my finding is any example, if anyone would like to optimize their
Outernet reception, or for that matter ANY L-band reception, you can do it
without dedicating one of the expensive SDR's to this function.  The
metal-case rtl-sdr dongle with bias-T enabled was an excellent step up in
performance for me.

-Scott,  K4KDR


On Wed, Oct 5, 2016 at 6:51 PM, Robert Bruninga <bruninga at usna.edu> wrote:

> AMSAT tinkerers?
> OUTERNET is a free worldwide Geostationary Satellite downlink system
> designed to bring content to remote areas all over the globe.  They have
> six geostationary birds covering the entire globe EVERYWHERE.  All you need
> is a small 18” (or 36” in some very remote areas) to receive content via
> your own home-made receiver based on a TV dongle and Rasberry Pi.
> Is there anyone on AMSAT-bb that is already receiving this content?  We’d
> like to hear about how easy it is to set up a receiver.
> We have some ideas on how this can be used to augment Ham radio in our
> Emergency Response and remote operations missions.  See
> http://aprs.org/outnet.html
> Bob, WB4APR

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