Working GreenCube digipeater

GreenCube satellite is a microgreens cultivation CubeSat satellite who have a MEO (Medium Earth orbit) that carrying a 1200 Bauds packet radio digipeater on UHF amateur radio band. MEO is a game changer because of his fantastic 5 800km apogee, it let work someone up to 13 000km versus 8 000 for Oscar 7 or RS-44 LEO satellites.

GreenCube have benn build by S5Lab a italian Space Systems and Space Surveillance Laboratory from Roma university. The digipeater has been developed in collaboration with AMSAT Italia.

My distance record QSO is 11761 km with A65BR but I am sure that the distance record is already more than 12 500km soon.

Due to this distance to satellite, this also need a very good setup with a high gain Yagi (10 elements) and good LNA to decode packets. With my setup I can decode packets with less than 5° of elevation but not more below even if I can hear the packets, loss don’t let me decode them.

Follow S5Lab on twitter for updates:

This is a simple description of how I did. You will to adapt to yours but maybe it can help you.

My hardware setup :
– Icom IC-9700 with 2 CAT interface
– 18 elements V/H polarization DK7ZB Yagi (10 dBi at least recommended)
– Yaesu G5500 rotator with EA4TX ARS-USB direct controler (not using the poor Yaesu controler)
– Low loss mast mounted LNA and Polarization mast switch with M5stack console

My software setup under Window 10 :
– PstRotator v17.28
– Omnirig
– SatPC32ISS v12.10

And for decode/transmit GreenCube packets:
– SoundModem by UZ7HO ver 0.05b
– DK3WN GREENCUBE Telemetry Decoder v1.1
– DK3WN GetKISS+ v.1.4.2 (Transfer to SATNOGs)

Icom IC-9700 USB have 2 ports that will let use the first serial port for PstRotator Doppler CAT control but you will also need the second IC-9700 serial port to let SoundModem control TX via PTT RTS command. You will need to update your IC-9700 settings to let change PTT control to the B port. To do that, you’ll need to go in Menu/SET, then Connectors,  USB SEND/Keying and then select “USB (B) RTS” in USB SEND Menu.

My Icom IC-9700 have AGC turned OFF for DATA modes that is very important for decode quality. Noise Blanker and Noise Reductor should be also turned OFF for digital communications. You should adapt Baud rate and of course Port.

You also need to check your IC-9700 setting while you are using USB-D (USA-DATA) mode. The USB audio card input need to be use in Set/Connectors/Mod Input/Data Mod, set-> USB. You you use USB, IC-9700 use the DATA OFF MOD parameter who is normally set to MIC.
It is really important to differentiate this 2 mods otherwise you will transmit your microphone audio during your transmission and nobody want to hear all the wickedness you say when you didn’t succeed to be digipeated 🙂
Also check that none of other software are using your USB card because nobody want to hear on the air the youtube video your are watching (or youp***). That’s a common mistake on FT8 frequencies :-/



Omnirig is a CAT interface for PstRotator and needed to be setup with your usual first port. Your setup will change from my configuration :

PstRotator antenna and Doppler correction :

Assuming you already have download, registered (yes, that’s ham radio life, it is not free but this software is really amazing even if a Linux version doesn’t exist) and also configured to run your antenna manually and had setup your home grid location. Then :

To access to Satellite tracking, you need to launch Tracker/Satellites and change mode de Tracking on main window then a new window will appear for Satellites Tracking. From this window, I will also be able to launch a third window with the Satellites Map.

Then you will need to update TLE in the Menu. You need to remove celestrak and add nasabare TLE file and click on update button :

Then in Satellites menu, you will need to add GREENCUBE:

Then in Favorites, you can click on Greencube, then click on the UP+DN button and enable “Use OmniRig” and your transceiver should start to use the same frequency than PstRotator screen. You may also need to change then mode to DIGR to have USB-D mode enabled.


If you succeed to have the same frequencies on your transceiver and PstRotator on both RX and TX (yes, you can click the TX button to test TX without audio).


SatPC32ISS need to be updated to version v12.10 or more to have ability to run GreenCube specificities.You need to add this line to Doppler.SQF :


If you already use SatPC32, you don’t need to change anything. Just adapt frequency in CAT window. I am using 435308.5 with GPSDO but you need to adapt it to your TCXO precision. USB-D is now supported by this version so you will not have to change to this mode manually and the Doppler correction don’t stop working in the middle of a pass like before.

Decoding GreenCube packets :

Now, you can start SoundModem and launch Settings, , you will then just need to select the second COM port of your Icom in “Select PTT port” in Settings. If you don’t know witch USB ports are used, you can take a look on your Windows Microsoft Management Console :

Due to Sound Card sample rate, Oliver DL6KBG advised me to set the TX/RX SampleRate to 12000 Hz (Maximum available value). You can also check Color waterfall than give you a better readable waterfall.

In Modem settings, you just need to check your TXDelay 400ms for old transceiver but 80ms of TXdelay and 1 ms tail is perfect for Icom IC-9700  but everything should be as default :


You need to check if you can send packet so please check you transmitting power is reduce to 0 and try to listen with a local receiver.

From this point, you need to wait a Greencube pass and try to receive packets. You will need to adjust Doppler to your receiver. Because I am using GPSDO source, I founded a -1 300 Hz difference but you will need to adjust it with arrow on the PstRotator window :

Before transmitting you have to wait if the transponder is active and you are able to receive all incoming packets. If not, don’t try to transmit! You will also have to wait until the Digipeater Status is no more undefined in the bottom page of GreenCube Digipeater software :

If the Digipeater is OFF, DO NO TRANSMIT. Command station is maybe sending data to the satellite, don’t disturb the operations but participate collecting the telemetry by sending them to SatNogs DB.

You will get a minimum of one packet each 45 seconds. It is the telemetry packet that you can send to SatNogs with both DK3WN software.

It is really easy to hear packets not so easy to decode it! GreenCube will be 6000 to 10000 km far away from you.

Polarization match, good decodes :

Polarization mismatch, no decodes :

Also check the arrow horizontal line is perfectly centered to the packet. PstRotator calculate doppler correction with a very high accuracy so you should not have to change it during a pass or maybe because of IC-9700 TCXO precision trouble. Because I am using my 9700 also for EME, I have a LeoBodnar GPSDO and injection board installed and that’s a good help for GreenCube Doppler correction as well.

If you have difficulties to decode packets bellow 20°, that’s normal. It is very challenging. But if you have difficulties upper than 20°, you need to check if:

– you have sufficient amount of gain from your antenna (7 elements is a minimum)
– you don’t have coaxial loss or LNA working
– your rotator don’t have positioning problem.
– your polarization (Circular is -3dB loss, wrong polarization is -20dB). I am adapting polarization under 20° for best reception to optimize decodes. If you loose packet for few minutes et get them few minutes : check the polarization harness or if switching is good. If you only have one polarization (horizontal or vertical), you will loose the digipeater frequently : During a pass, satellites antennas looks vertical to horizontal due to relative orientation (the satellite don’t change is orientation but you are changing).

Use the Digipeater :

If the Digipeater is ON, DON’T TRANSMIT packets if you can’t read it! Respect the usual Amsat rules : Don’t call CQ more than one per minute, don’t try to do more than one qso at a time. Don’t call CQ or answer if there is already too much qso in progress.

GreenCube Digipeater software is a great piece to be able to make qsos. Macros let do easy stuff but MSG input text area let you transmit specific messages. More long is the message, more it will take to be transmit and more the errors risk is high.
The digipeater is a store and forward packets. The ReTX Delay is the delay after the digipeater will retransmit your packet. If the delay equal to 0 (that I recommend), the digipeater will retransmit your packet as soon you will transmit it. If the delay is more than 0, the digipeater will answer you a ACK packet that will add more traffic on the digipeater. If you use this function, please don’t call CQ but use it to send your greetings to other continents based to the time in second the bird will moved to this part of the world.
Most of the time, your first goal will be to make qsos with stations around so this delay need to be to 0.

To give the best chance to be decoded use short message and restrict your message’s length to essential datas.

Not a good idea :
CQ DE XXXXX Michael in Boumourt sur Oise BA22ZE85 <-:>

Good idea :

Read and Send the telemetry to SatNogs :

Telemetry packets each 45 seconds :

DK3WN GREENCUBE Telemetry Decoder software in action. You just need to click on TCP client to enable it.

DK3WN GetKiss+ software. It will allow you to send packets to SatNogs database. To enable it, you will need to check TCP Client and select GREENCUBE in the top right select menu and then , in TLM Forwarder tab, select allow data transfer to NORAD ID 53106.

SatNogs GreenCube telemetry dashboard :

A huge thank you to Scott K4KDR and Doug K8DP for the great help provided to me to be able to get on this bird.

  • FG8OJ
  • Bertrand "Burt" FG8OJ is an amateur radio who has been passionate about radio for almost 40 years. I like all activities: tweaking my station, making antennas, doing DX on HF, doing satellite and EME. I also love participating in HF contests or in Europe in VHF/UHF. Everything excites me.


  • Thanks for the great summary and tips Burt…. Yesterday I did my initial basic set-up ready for testing. Hope to work you soon! Nick M1DDD

    • It will be great to see there Nick, 73!

  • Hope to catch you soon on GC !

    • That’s great article Burt FG8OJ!
      I shall be trying to keep ready my setup soon & work via this bird. This satellite attract me due to MEO Orbit (to work large footprint). Also I liked space vegetation experiment carried out on this 3U bird, just amazing.
      Again thanks for all your great efforts to make this article available for us.
      Rajesh Vagadia VU2EXP

  • Excelente information I will put it into practice I copy it with 6 element directional but I have not encoded the frame, I hope to copy it soon via GC! 73dx´S YV6AE GRID: FJ79

  • Great article! Thank you, and now I do not need to write an article at AMSAT-SM website 🙂
    73 Lars SM0TGU

  • TNX Burt for info
    73 de Paulo PV8DX

  • Excellent guide to learn how to work the SAT thanks Burt, XE1KW Omer 🇲🇽

  • Excellent guide to learn how to work the SAT thanks Burt, XE1KW

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