[amsat-bb] Lilacsat-1 QSO - Could be first over US?

Scott scott23192 at gmail.com
Fri Jun 2 07:55:14 UTC 2017

Thanks Bob, a real thrill to be one of the first to have success with a new satellite.  

I know that using a computer to extract voice from a data stream on the receive side adds complexity, but it was a fun challenge to get working.  One side benefit is that you can record & replay the entire satellite pass because the whole QSO is received as computer data and saved as a file.  

I have uploaded a video made while replaying my contact with Bob; that can be found at:  https://youtu.be/BjWZJBBcQfQ

Also, I re-recorded the audio recording that Bob made at his end to a .wav file that might be easier for Windows users to play.  That can be found at: 


If you watch the YouTube video, you'll hear that I received Bob's signal from the satellite much better than my own.  This is for a number of reasons that everyone on this list is already familiar with, but I wanted to list them anyway since using a computer to decode a voice stream from data might be new to some.

#1, Bob knew what he was doing.  This was maybe my 4th or 5th satellite contact

#2, the satellite was at a much higher elevation for Bob; from my house it was much lower in the sky and it's summer in the U.S. & I'm surrounded by trees full of leaves

#3, when you hear my audio, that is coming down from the satellite at the same time I'm transmitting, so we're in a full-duplex situation.  Fortunately, my SP-70 pre-amp and Airspy SDR receiver combine to block out most of the attenuation caused by the 2-meter uplink

... I'm only going into this detail to illustrate that this isn't so different from any other satellite QSO.  So, I hope many others will get setup to decode this digital downlink.  I've seen many of the more experienced folks already using SDR's for their receive radio, so this isn't much different from that - you just need to run software that's more involved than HDSDR or SDRSharp.

It would be a challenge to teach Linux from scratch remotely, but beyond that with the GNU Radio portion of this, I'll be glad to help anyone who has the basics in place and just needs a hand with the details.  There's a 100% guarantee that you'll be much more experienced with satellites than I am, but maybe I've done more on the computer side than a portion of the people out there.  Anyway, glad to help if I can.


-Scott,  K4KDR
Montpelier, VA  USA


From: Robert Mattaliano 
Sent: Friday, June 02, 2017 1:28 AM
To: amsat-bb at amsat.org 
Cc: Scott 
Subject: Lilacsat-1 QSO - Could be first over US?

Just completed QSO with Scott K4KDR in VA (FM17) from RI (FM41) on Lilacsat-1.  This may very well be the first digital amateur downlink QSO over the US. Thanks Scott!   

DK3WIN and GI7UGV were also successful across the pond a few days ago.  Congrats guys! 

Recall that Lilacsat-1 is among the QB50 constellation recently launched from the ISS.  This bird is has a Codec2 1300bps digital downlink.  Setting up the decoder requires an SDR for RX on a Linux platform.  

A few hints - run low power (5-10 watts), keep mic gain down for better audio clarity, watch out for desense since 2M up and 436 down with the SDR

More information at http://lilacsat.hit.edu.cn/?page_id=257.  Tks BG2BHC and the Harbin team.  
Also, a lower latency decoder from EA4GPZ at http://destevez.net/2017/05/low-latency-decoder-for-lilacsat-1/#more-2671.  
M6SIG also has an updated ISO here https://t.co/vmARZqIBoU

Hope to hear you on,


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