Preliminary Design
Version 5 (J. Simmons, 12/24/2013 10:17 am)
| 1 | 1 | Jeremy Wright | h1. Preliminary Design |
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| 2 | 1 | Jeremy Wright | |
| 3 | 2 | J. Simmons | {{toc}} |
| 4 | 2 | J. Simmons | |
| 5 | 2 | J. Simmons | h3. Introduction |
| 6 | 2 | J. Simmons | |
| 7 | 4 | J. Simmons | This document covers the preliminary design decisions for the *Ground Sphere* ground station. The document includes three sections: technical background on *SkyCube's* radio, hardware design of *Ground Sphere*, and software design of *Ground Sphere*. The design is structured in parallel with the [[Requirements Document]] to ensure all requirements are satisfied. |
| 8 | 2 | J. Simmons | |
| 9 | 2 | J. Simmons | h3. SkyCube Radio Details |
| 10 | 2 | J. Simmons | |
| 11 | 2 | J. Simmons | ... |
| 12 | 2 | J. Simmons | |
| 13 | 3 | J. Simmons | h3. Hardware Design of Ground Sphere |
| 14 | 1 | Jeremy Wright | |
| 15 | 3 | J. Simmons | * TR 1.1 Enable users to receive "space tweets" |
| 16 | 3 | J. Simmons | ** TR 1.1.2 Receive radio signals on 915 MHz |
| 17 | 3 | J. Simmons | *** Antenna |
| 18 | 5 | J. Simmons | **** Dimensions ("source":https://opendesignengine.net/news/46 | "link budget":https://opendesignengine.net/news/50) |
| 19 | 5 | J. Simmons | ***** Phasing line: 2.7745" of RG-62 90 ohm coax cable |
| 20 | 5 | J. Simmons | ***** Ground plane: 6.3" diameter disk of conductive rip stop fabric |
| 21 | 5 | J. Simmons | ***** Ground plane radial arms: 2.3925" of rigid material (need not be conductive) |
| 22 | 5 | J. Simmons | ***** Aerial length (circumference): 13.7075" of 12ga copper wire or better |
| 23 | 5 | J. Simmons | ***** Distance between bottom of aerials and ground plane: 1.6475" |
| 24 | 3 | J. Simmons | *** "Preamp":http://www.g0mrf.com/432LNA.htm |
| 25 | 1 | Jeremy Wright | *** "RTL2832U SDR":http://www.realtek.com.tw/products/productsView.aspx?Langid=1&PFid=35&Level=4&Conn=3&ProdID=257 |
| 26 | 5 | J. Simmons | * TR 1.2 Be easy to assemble from kit components |
| 27 | 3 | J. Simmons | ** TR 1.2.1 Time to assemble |
| 28 | 3 | J. Simmons | *** Ground station will be shipped as a kit |
| 29 | 3 | J. Simmons | ** TR 1.2.2 Tools for assembly |
| 30 | 3 | J. Simmons | *** Preamp will ship already assembled, ground station structure will include all drill holes and all other component fabrications steps |
| 31 | 3 | J. Simmons | * TR 1.3 Have low shipping costs for the packaged kit |
| 32 | 3 | J. Simmons | ** <insert max dimensions here?> |
| 33 | 3 | J. Simmons | * TR 1.4 Operate using a modern Windows PC |
| 34 | 3 | J. Simmons | ** TR 1.4.3 Hardware must connect to PC using standard port(s) |
| 35 | 3 | J. Simmons | *** The SDR connects to host computer through USB 2.0 |
| 36 | 3 | J. Simmons | * TR 1.5 Hardware must be robust |
| 37 | 3 | J. Simmons | ** All connectors will be designed to ensure long life (internally mounted, have adequate strain relief, etc) |
| 38 | 3 | J. Simmons | * PR 2.1 Budget |
| 39 | 3 | J. Simmons | ** PR 2.1.1 Unit cost |
| 40 | 3 | J. Simmons | *** <insert current materials cost here from BoM> |
| 41 | 3 | J. Simmons | |
| 42 | 3 | J. Simmons | h3. Software Design of Ground Sphere |
| 43 | 3 | J. Simmons | |
| 44 | 3 | J. Simmons | * TR 1.1 Enable users to receive "space tweets" |
| 45 | 3 | J. Simmons | ** TR 1.1.1 Predict SkyCube flyover opportunities |
| 46 | 3 | J. Simmons | *** Using "GPredict":http://gpredict.oz9aec.net for flyover prediction |
| 47 | 3 | J. Simmons | ** TR 1.1.2 Receive radio signals on 915 MHz |
| 48 | 3 | J. Simmons | *** SeeDeR software (provided by Southern Stars) can tune SDR to 915 MHz |
| 49 | 3 | J. Simmons | ** TR 1.1.3 Decode "space tweet" message from SkyCube |
| 50 | 3 | J. Simmons | *** SeeDeR software (provided by Southern Stars) can decode the BPSK-modulated, unencrypted AX.25 data packets sent at 9600 baud "space tweets" sent out by *SkyCube* |
| 51 | 3 | J. Simmons | ** TR 1.1.4 Account for Doppler shift |
| 52 | 3 | J. Simmons | *** SeeDeR software (provided by Southern Stars) will be updated to account for Doppler shift |
| 53 | 3 | J. Simmons | * TR 1.4 Operate using a modern Windows PC |
| 54 | 3 | J. Simmons | ** TR 1.4.1 Software must run on Windows |
| 55 | 3 | J. Simmons | *** GPredict runs on Windows 7 |
| 56 | 3 | J. Simmons | *** SDR drivers <get link from Aaron> run on Windows 7 |
| 57 | 3 | J. Simmons | *** SeeDeR runs on Windows 7 |
| 58 | 3 | J. Simmons | ** TR 1.4.2 Software must be easy to install |
| 59 | 3 | J. Simmons | *** GPredict includes a Windows installer |
| 60 | 3 | J. Simmons | *** SDR drivers include a Windows installer |
| 61 | 3 | J. Simmons | *** Southern Stars will provide a Windows installer for SeeDeR |