YouTube Video of Africube Satellite at AMSATSA

 AfriCUBE Cubsat.

YouTube Video of Africube Satellite at AMSATSA

Some feedback on the AfriCube Satellite

 

How to Create a Linear Transponder using a RTL Dongle and HackRF with Gnu Radio.

How to Create a Linear Transponder using a RTL Dongle and HackRF with Gnu Radio.

I wanted to test the concept of a linear Transponder and how difficult would it be to build it with conventional components.

Hardware Configuration

Hardware required to build the Transponder.

1. SDR IQ demodulator with rtl dongle (RF In)
2. SDR IQ DSP processing system. Gnu Radio (DSP processing)
3. SDR IQ Modulator. HackRF (RF Out)
4. Background management system. (OBC) for additional telemetry.

Software required for Transponder.

1. SDR IQ demodulator. rtl dongle (RF In)
2. SDR IQ DSP processing system. Gnu Radio (DSP processing)
3. SDR IQ Modulator. HackRF (RF Out)
4. Background management system. (OBC)

Video of working Transponder.

Gnu Radio.

Transponder Block Diagram

RTL SDR Block.

RTL-SDR Source

Low Pass Filter Block.

 

Low Pass Filter Block

AGC Block.

AGC Block

Power Squelch.

Power Squelch

Osmocom Sink. (HackRF)

Osmocom Sink (HackRF)

FFT. (Spectrum View of input)

FFT Spectrum View

REF: Power point Slides at AMSAT SA

Ref:Source code is available on Github Version 4

How do you build a 1U Cube-Sat Linear transponder using SDR / DSP technology with limited Power?

How do you build a 1U Cube-Sat Linear transponder using SDR / DSP technology with limited Power?

Requirements:

Satellite requirements.

1. Linear Transponder 70cm (437Mhz) up-link and S band (2.4GHz or 1.2Ghz down) Down-link (Bandwidth ? 250Khz on 70cm ?)
2. Satellite Low Earth orbit (LEO) altitude between 650 kilometers. We need this so we can calculate path loss and RF power and antenna gain requirements.
3. Available Power 1.5W for transponder from Solar panels and battery system.
4. Telemetry mode? CW / AX25 / AFSK 9k6 /....  
1. UHF Beacon recomendation.
   • UHF Beacon interval:  about 55 seconds
   • UHF Transmit power: ~ 1 W
   • AFSK AX25 1k2 and fallback of CW 10WP 
5. Satellite antennas for 70cm ? and (Polarization ?) 
6. Satellite antennas for 2.4Ghz / 1.2Ghz and (Polarization ?) 
7. Telemetry Requirements ? (ID, Temperature, Power in, Power out, Battery left, Transponder Mode status, Antenna Status, Satellite Orientation, ........)
8. Inter board Connector Specification (PC/104 communication)
9. OBC, SOLAR,charger,Orientation and Battery from existing Satellite ?
10. 1 U Cube-Sat Space frame from existing Satellite (10x10x10) 1kg
11. DSP 10 to 14Bit A/D /D/A Dynamic range. what is good enough ?
12. PCB Board size details PC104 with cutouts for wire.
13. Space frame and Solar panel frame and Antenna deployment. (out of scope)
14. Solar panels. (Out of Scope)
15. Power regulator and Charge regulator and Battery. (out of Scope)
16. Orientation controls. (out of scope) (Stabilization)
17. RF Linear Transponder using SDR / DSP. (70cm up 2.4Ghz or 1.2Ghz down)
18. OBC (In scope ARM M4 or possibly A9) (FreeRTOS)
19. Inter board communication standard.

Out of Scope for now:

1. Space frame, Solar panels and panels frame.
2. Solar panels
3. Power regulator and Charge regulator and Battery.
4. Orientation controls.

In scope for now:

1. Linear Transponder using SDR / DSP. (ARM Processor possibly not FPLG due to power constraint.)
2. Telemetry TX
3. Command control RX

Block diagram.

Transponder SDR transmitter. (Down-link 145.9?? MHz USB) (not confirmed) (250Khz)

Telemetry transmitter

• Estimated TX full power for beacon and transponder (300 mW) when Sat is in sunlight.
• When satellite is in eclipse low power of about (30mW). 

Transponder SDR receiver. (Up-link 435.??? MHz LSB ) (not confirmed) (250Khz)

• Estimated maximum TX up-link power of 5 watts with a 7 dBi gain antenna. 

Beacon / Telemetry

Here are several DDS signal generators I'm looking at:

1. AD9833  0 - 12.5 Mhz 
2. AD9850  0 - 50 Mhz
3. AD9851  0 - 70 Mhz 
4. Si5351    0 - 150 Mhz
5. Si5351A 0 - 290 Mhz
6. AD9959  0 - 500Mhz
7. AD9952  0 - 500Mhz Practical max 160Mhz depending on patern

Ref : Examples code for the STM32f4  and AD9850  https://zissisprojects.wordpress.com/2015/01/24/stm32-f4-discovery-and-ad9850-dds/

1.2Ghz band plan for Downlink

TX

1. https://github.com/F5OEO/rpitx
2. http://ebrombaugh.studionebula.com/radio/txdac/index.html
3. https://www.etherkit.com/rf-modules/si5351a-breakout-board.html
4. http://www.simplecircuits.com/files/Download/QEX_release.pdf
5. http://www.amrad.org/projects/sdr/
6. https://myriadrf.org/projects/rdk/
7. http://www.eevblog.com/forum/projects/the-sdr32-a-stm32-based-software-defined-radio/
8. http://www.stm32-sdr.com/styled/index.html  (PSK)
9. https://wiki.analog.com/resources/eval/user-guides/ad-fmcomms2-ebz/software/baremetal?rev=1395324588#code_size_information ( AD9361 NON OS Drive)
10. https://github.com/GomSpace/libcsp (Cubesat Space Protoco)
11. https://github.com/robots/APRS  (STM32 APRS code)
12. https://michaldemin.wordpress.com/2012/02/27/cheap-afsk-tnc/  (AFSK stm3  2)
13. https://github.com/athirasubhash/AX25MODEM (AX25 for STM32)
14. www.analog.com/en/education/education-library/videos/3845680080001.html (Video Analog devices)
15. https://datasheets.maximintegrated.com/en/ds/MAX2837.pdf  (IQ front end Maxim)
16. https://www.maximintegrated.com/en/products/analog/data-converters/analog-front-end-ics/MAX5863.html (A/D and D/A MAXIM)
17. https://github.com/mossmann/hackrf/blob/master/firmware/common/max2837.c (max2837 c Library)
18. http://www.g4jnt.com/DDSVHFBeaconDriver.pdf  (DDS beacon generation)

Possible def tools.

1. GNU radio
2. Math lab
3. ARM DEV board tools. (How to setup Eclipse for Arm development)
4. Real time OS https://istarc.wordpress.com/2014/08/04/stm32f4-behold-the-project-wizard/
5. Installing FreeRTOS on STM32F4 https://istarc.wordpress.com/2014/07/10/stm32f4-deploy-freertos-in-under-10-seconds/

Ref :

1. http://sigalrm.blogspot.co.za/2012/09/stm32f4-discovery-quick-start-guide.html
2. https://groups.google.com/forum/#!searchin/mbed-devel/stm32f4$20discovery%7Csort:relevance

What a satellite frenzy

What a satellite frenzy.

Satellite prediction software Gpredict

Not more that a year ago you would not have seen anything like this. Its satellite heaven.

I was looking at the Gpredict screen this morning and could not believe what was happening.

There was 5 Amateur Satellites (ZACUBE-1, FUNCUBE, EAGLE2,DELFI-N3XT,CUTE-1.7  ...) above me and I had a quick look at the webSDR and could see multiple beacons all over the screen. Well there is now no excuse not to work satellites. You can pick and chose, Packet store and foreword FM transponders and Linear transponders, some even have cameras on board. What fun!. Some of the Satellites like the FM transponders can be communicated with a simple HF handheld transceiver. ($50 max)

Enjoy the Satellites.

New Amateur radio Cubesats will be launched from the International Space Station on Thursday, February 6, 2014.

New Amateur radio Cubesats will be launched from the International Space Station on Thursday, 6 February 2014. ( 18:07 UTC) new date (February 28 at 07:30 UTC)

1) LituanicaSat-1 (

• Onboard VGA camera
• GPS receiver.
• UHF CW beacon 100mW, 9k6 AX25 FSK telemetry TX 2 watts.
• FM Mode V/U transponder 150mW Voice Repeater.
• 145.950 Mhz Uplink FM transponder.
• 435.180 MHz Downlink FM.
• 145.850 MHz AX25 Uplink.
• 437.550 MHz AX25 Downlink.
• 437.275 MHz CW Beacon .
• https://www.facebook.com/Lituanicasat1

2) LitSat-1

• Beacon/TLM down link 145.850 MHz
• Beacon RF packets are AX.25 UI frames https://www.tapr.org/pub_ax25.html Main parameters of the beacon frames are: TX baud rate 9600 bps (G3RUH), repetition period ~4.5s, beacon duration ~0.5 s, source call address – TNC, destination call address – LY1LS.

Linear Transponder details

• Uplink 435.150 MHz LSB 
• Downlink  145.950 MHz USB 
• Bandwidth ±15 kHz from centre
• CW beacon   435.1375 MHz (LY1LS/B)
• Normal mode – transponder, beacon OFF
• 437.550 MHz AX25 Uplink.
• 145.850 MHz MHz AX25 Downlink.
• LitSat-1 on Facebook https://www.facebook.com/palydovas
• 
  

3) UAPSAT

• 145.980 MHz AX.25 Packet Radio uplink.
• 437.385 MHz downlink.
• http://www.uap.edu.pe/

4) ArduSat-2

• 437.? MHz 9k6 MSK CCSDS downlink.
• http://www.kickstarter.com/projects/575960623/ardusat-your-arduino-experiment-in-space

5) UKube-1
The Ukube-1 Satellite was lunched on 8 July at 18:32:42 UTC. kep details at http://www.dk3wn.info/p/?p=46812UKube-1 CW was confirmed over Europe ;-)

UKube-1 communications subsystem:

• Telemetry downlink 145.840 MHz

• FUNcube subsystem beacon 145.915 MHz

• 400 mW inverting linear transponder for SSB and CW

- 435.080 -435.060 MHz Uplink

- 145.930 -145.950 MHz Downlink

• 2401.0 MHz S Band Downlink

• 437.425-437.525 MHz UKSEDS myPocketQub Downlink

More details is available from http://amsat-uk.org/2014/02/04/ham-radio-cubesats-to-deploy-thursday/