# TinyGS vs. SatNOGS: A Comparative Analysis of Open-Source Satellite Ground Station Networks
## 5 Discussion
### Comparison of Costs  
GS construction costs vary according to the chosen components. Before proceeding to outline the costs for each scenario, it is crucial to emphasize that the list of components presented is based on items recommended by these projects and their corresponding online prices at the time of writing this article, specifically in August 2023 and for Portugal. This implies that the reader has the flexibility to purchase alternative components or build their own components, ultimately reducing the overall expenditure. Additionally, during the cost calculation, all components (LNA, Filter, etc.) will be included. However, the reader is not obligated to purchase all of them. For instance, in cases where there is a minimal presence of FM signals, the acquisition of a filter may not be necessary. If one opts for a TinyGS, the costs are shown in Table 2 and will cost at least EUR 119. In addition, one may need to buy coaxial cables, SMA adapters, outdoor protective housing, etc. However, these expenses are not accounted for because they depend on the objectives and where one is going to build the GS. Still, with respect to Table 2, an LNA with a built-in Upotronics bandpass filter was chosen. Its price is relatively high, but, within the recommendations on GitHub [9], it was the only one obtainable in Portugal. If one chooses to build a fixed SatNOGS GS in accordance with the recommended materials, but with the same TinyGS antenna, the costs are around EUR 164, as can be seen in Table 3. This increase is mainly due to the presence of the SDR. The LNA present in Table 3 can be powered by a bias tee; however, it is also possible to power it with an external source according to RTL-SDR.com. If one wants to work with a bias tee, one will need to enable the built-in bias tee in RTL-SDR because, by default, it is turned off. Furthermore, if the LNA is bias tee powered, the filter may prevent the bias tee from getting to the LNA. In that case, one should put the filter between the antenna and the LNA; however, one may \begin{table}
\begin{tabular}{c c c} \hline \hline
**Scenario** & **Difficulty** & **Time** \\ \hline Fixed SatNOGS GS (Without & & \\ building the omnidirectional & 2 & 1 \\ antenna) & & \\ \hline Fixed SatNOGS GS (Building & 4 & 2 \\ the omnidirectional antenna) & & \\ \hline Rotator SatNOGS GS (Without & & \\ building the directional & & \\ antenna, rotator and & 3 & 1 \\ controller) & & \\ \hline Rotator SatNOGS GS & & \\ (Building the directional & & \\ antenna without building & 4 & 2 \\ rotator and controller) & & \\ \hline Rotator SatNOGS GS & & \\ (Building the rotator and & 5 & 3 \\ controller without building & & \\ the directional antenna) & & \\ \hline Rotator SatNOGS GS & & \\ (Building the rotator, & & \\ controller, and the directional & & 4 \\ antenna) & & \\ \hline \hline \end{tabular}
\end{table} 
Table 1: _Cont._obtain worse results. If one does not have a strong presence of FM signals, one can always remove the filter and see if this produces better results. Concerning the construction of a rotator SatNOGS using a SatNOGS rotator v3, the associated costs amount to approximately EUR 884, as detailed in Table 4. In this particular GS, given the inclusion of a rotator, the omnidirectional antenna is replaced with a directional one, specifically the Wimo X-Quad [17]. Although this antenna comes with a higher price tag, it serves as a reference and is recommended if one opts for a commercial alternative. Nevertheless, significant cost savings can be achieved by constructing one's own antenna. Examples include the QFH and the SatNOGS helical antenna, both of which yield satisfactory results [20]. The cost of the rotator and the controller includes expenses for 3D printing and online purchases. Opting for commercial rotators might escalate the overall cost--for instance, choosing the Yaesu G-5500 could increase the cost to over EUR 700.