The purpose of this thesis is to design FSK modem for Packet communication. In accordance with accessible literature was constructed functioning circuit schema and subsequently there was constructed a motherboard which is mainly assembled from SMD technology. It makes this modem mobile and very easy usable in terrain. Modem communicates with PC via USB bus. Also this bus is used as power source for this device. Communication between modem and PC is realized by KISS protocol and connection with tranciever is realized by AX.25 protocol.

No description available.

APRS system is described are sent toin my essay, which is used for sending and receiving text messages. The text messages frequenc 144 MHz by using the modulation scheme AFSK. APRS communicate by using the protocol AX 25, which sends and receives the text messages in the area where are carried despatches and control bits as well. The whole area of high frequency part is in one integrated circuit. The control, coding and decoding of the area is the microcontroller’s job.

APRS system is described are sent toin my essay, which is used for sending and receiving text messages. The text messages frequenc 144 MHz by using the modulation scheme AFSK. APRS communicate by using the protocol AX 25, which sends and receives the text messages in the area where are carried despatches and control bits as well. The whole area of high frequency part is in one integrated circuit. The control, coding and decoding of the area is the microcontroller’s job.

Thesis (MEng)--Stellenbosch University, 2014. / ENGLISH ABSTRACT: Nano-satellites are mostly used in lower earth orbit applications, where communication intervals are limited, often to a combined total of less than one hour per day. With these type of inherent limitations of lower earth orbits, there are also the physical size and equipment restriction of nano-satellites to consider, especially those of the CubeSat specification. It is of critical importance to use the limited time and communication resources as effectively as possible. The network protocol has a huge influence on reliability and throughput of a satellite network. An important requisite for designing, comparing and improving network protocols is a network protocol simulator, that is able to envisage the design results. Simulation can facilitate rapid development and unforeseen discoveries. Very little information is currently available regarding communication protocols used in nano-satellites. This thesis aims to explore and improve the current status of nano-satellite network simulation, as well as to demonstrate the development of an improved communication protocol strategy. It was found that there is a lack of proper simulation tools for satellite networks, which led to the development of SatSim. SatSim is a discrete event network simulation tool, developed in Python, which can be used to develop and analyse network protocols. SatSim was verified by comparing simulation results with other published results, which made use of different software tools and theoretical throughput calculations. AX.25 is one of the most commonly used network protocols in the nano-satellite industry. It was implemented in SatSim and verified with theoretical throughput calculations, as no other simulation data on AX.25 was available. AX.25 was used as a baseline protocol to improve upon. FX.25 was developed by the Stensat Group in an attempt to improve AX.25. FX.25 adds forward error correction to AX.25, by wrapping additional data around the AX.25 frames. This method maintains backward compatibility with AX.25. FX.25 was implemented in SatSim and the simulation results proved that FX.25 was a more reliable protocol than AX.25, as it can communicate at lower elevations and over noisier communication channels. However, the drawback of the additional forward error correction is the increased overhead, which reduces the overall payload data throughput. A modular AX/FX.25 protocol was then implemented in SatSim, to exploit the strengths of both protocols. This hybrid protocol yielded significant improvements to data throughput and can enable future software defined radio or hardware developments. / AFRIKAANSE OPSOMMING: Nano-satelliete word hoofsaaklik gebruik in lae-aard wentelbaan toepassings waar kommunikasietyd beperk is, soms tot minder as een uur per dag. Gepaardgaande met hierdie inherente beperking van lae-aard wentelbane, is daar ook die verminderde omvang en kapasiteit van nano-satelliete, veral ten opsigte van die CubeSat spesifikasie. Effektiewe aanwending van die beperkte tyd en kommunikasie-hulpbronne is dus noodsaaklik. Die keuse van netwerk protokol het ’n beduidende invloed op die betroubaarheid en data deurset van ’n satelliet netwerk. ’n Belangrike voorvereiste vir die ontwerp, vergelyking en verbetering van netwerk-protokolle, is ’n netwerk simulator. Beperkte inligting is tans beskikbaar oor kommunikasie protokolle in nano-satelliet toepassings. Hierdie tesis fokus op die verbetering van nano-satelliet netwerk-simulasie, asook die ontwikkelling van ’n verbeterde netwerk-protokol strategie vir nano-satelliet toepassings. Dit het na vore gekom dat daar ’n leemte is in die beskikbaarheid van simulasie sagteware wat gerig is op die ondersoek van satelliet netwerke. Hierdie waarneming het die ontwikkeling van SatSim genoop. SatSim is ’n diskrete-gebeurtenis netwerk-simulasie sagtewarepakket wat in die Python programmeertaal ontwikkel is om netwerk protokolle te ontwikkel en te analiseer. SatSim was geverifieer deur simulasies te vergelyk met die resultate van ander navorsingspublikasies, wat van verskillende sagtewarepakkette gebruik gemaak het, sowel as teoretiese deursetberekeninge. AX.25 is een van die netwerk protokolle wat mees algemeen in die nano-satelliet bedryf voorkom. AX.25 was geïmplementeer in SatSim en geverifieer met teoretiese deursetberekeninge. AX.25 was gebruik as ’n grondslag om op te verbeter. FX.25 was ontwikkel deur die Stensat Group in ’n poging om op AX.25 te verbeter. FX.25 voeg vorentoefoutkorreksie by tot AX.25, deur addisionele data tot die AX.25 netwerk pakkies te voeg. Hierdie benadering bewerkstellig agteruit-verenigbaarheid met AX.25. FX.25 was geïmplementeer in SatSim en simulasieresultate dui daarop dat FX.25 ’n meer betroubare protokol is as AX.25, omdat dit teen laer elevasiehoeke en oor swakker kommunikasiekanale kan kommunikeer. Die verbeterde betroubaarheid is ten koste van datadeurset, as gevolg van die toevoeging van die vorentoe-foutkorreksiedata. ’n Modulêre AX/FX.25 protokol was geïmplemeteer om te kapitaliseer op die sterk eienskappe van beide protokolle. Hierdie hibriede protokol het ’n beduidende verbetering gelewer ten opsigte van data deurset en kan toekomstige sagteware-gedefinieerde radio en hardewaretoepassings stimuleer.

In this thesis, we present the design and implementation of a CubeSat receiver system using the Universal Software Radio Peripheral (USRP) and GNU Radio. The goal of this project is to develop a low-cost and flexible ground station capable of receiving telemetry and payload data from CubeSats in real time. The CubeSat receiver operates in the UHF frequency range with a center frequency of 435 MHz and uses a software-defined radio (SDR) approach to provide wideband signal processing and demodulation capabilities. The satellite transceiver transmits an Ax.25 Transciever packet every 1 second using the Pumpkin CubeSat kit programmed in MPLab. To achieve this goal, we discuss the design considerations for the receiver system, including the selection of suitable hardware components and the development of custom software blocks in GNU Radio. We also developed the GFSK-based transmitter and receiver in GNU Radio, as well as a tracking system for the satellite. To decode the Ax.25 radio packet transmitted by the Pumpkin CubeSat kit, we developed an Ax.25 deframer in GNU Radio to decode the received signal. Our results demonstrate that the CubeSat receiver is capable of receiving and demodulating AX.25 formatted radio signals from Transciever. Additionally, we show that the receiver system is scalable and can be easily adapted for use with other CubeSat missions. Overall, our work provides a practical solution for CubeSat communication and lays the groundwork for future developments in low-cost CubeSat ground station technology.