updated faq page with com, added com hardware page

Author: balotofi

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_site/index.html

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+---
+title: COM Hardware
+parent: For COM Team Members
+nav_fold: false
+layout: default
+lang: en
+---
+
+# COM Hardware
+{: .no_toc }
+
+time to complete: 7 mins
+{: .label}
+
+
+<details markdown="block">
+<summary>Table of Contents</summary>
+
+- Table of Contents
+{:toc}
+
+</details>
+
+# 📡 Communications (COMM) Subsystem Guide
+
+This page covers key practices, materials, configurations, and frequently asked questions related to the COMM subsystem of the BIRDS satellite project.
+
+---
+
+## 🔑 Uplink Detection Codes
+
+> **Q: Can multiple uplink detection codes be set? How are they controlled or differentiated?**
+> **Tag**: Uplink
+
+Yes, it is technically possible to set multiple uplink detection codes. However, the current BIRDS configuration uses a single uplink detection code, and this has proven sufficient for its mission requirements.
+
+---
+
+## 📡 Antenna Design & Assembly
+
+### 1. **Antenna Connection Materials**
+
+* **Wire Type**: Leads from DIP resistors
+* **Surface Preparation**: Sanded with sandpaper
+* **Connection Method**:
+
+  * Lead wrapped 1.5 times clockwise around a bolt (2 mm gap), then tightened
+  * Example PhotoMOS for nichrome wire heating: **AQZ102** (DIP part with bent leads for SMD mounting)
+  * [AQZ102 on Digikey](https://www.digikey.com/en/products/detail/panasonic-electric-works/AQZ102/)
+
+### 2. **Antenna Fixture (White POM Resin)**
+
+* Designed and processed locally (e.g., Kyushu University workshop)
+* Alternatively, use general-purpose metal manufacturing companies
+
+### 3. **Antenna Wire and Hole Drilling**
+
+* **Vendor**: Osaka Heat Treatment Co., Ltd. (material only, not hole processing)
+* **Recommendation**: Use external companies for hole drilling due to breakage risks
+* **Nichrome Coil**: Can be handmade in the lab (no need to outsource)
+
+---
+
+## 🛰️ Antenna Type and Cable Management
+
+### 4. **Antenna Types**
+
+* Typically **monopole** or **dipole**
+* Operate in **UHF/VHF bands**
+* Refer to the subsystem’s **design document** for exact specifications
+
+### 5. **Coaxial Cable Length**
+
+* BIRDS used **180 mm** cables; excess cable was tucked between the antenna board and RAB
+
+### 6. **Cable Routing and Fixation**
+
+* **Route**: From COMM board (UHF TRX) top side (+Z) to the antenna board
+* **Fixation**:
+
+  * Use tape to suppress vibration
+  * During FM assembly: SMA connector torqued to **56 N·cm**, a small amount of **Araldite epoxy** applied (avoid threading area)
+
+---
+
+## 🔧 Drilling Thin Elements
+
+### 7. **Fixing and Drilling Methods**
+
+* Use **scribing** for positioning
+* Drill with wood backing; scrape rather than pierce
+* Drill press must be in good condition (check bit quality)
+* For batch drilling, use metal scrap fixtures with upper templates
+
+---
+
+## 📶 Amateur Band Considerations and Uplink Security
+
+### 8. **Frequency Use & Encryption**
+
+* **Regulation**: Both **uplink and downlink** must benefit the amateur community
+* **Kyutech Policy**:
+
+  * Uplink commands are **not encrypted** (encryption not permitted in amateur service)
+  * **Pseudo-encryption**: Actual frequencies hidden (e.g., “430.XXX \[MHz]”)
+  * Uplink frequencies removed or masked in internal/public presentations
+
+> ✅ As per UNISEC’s coordination guide, pseudo-encryption of uplinks is acceptable if command content is not publicly disclosed.
+
+---
+
+## 📊 Link Budget Calculation
+
+### 9. **Excel Tool Usage**
+
+* **Input Frequency**: Row 3
+* **Receiver Sensitivity**: Row 31 (based on COMM board test data)
+* Reference File: `119_120_121_BIRDS-5 LinkMargin.xlsx`
+
+### 10. **Adding a Preamp (31 dB)**
+
+* Added in **Row 28 (Downlink Summary)** as `Preamp[dB]`
+* Adjusted signal power at LNA input by including preamp gain
+
+> ⚠️ Preamp amplifies signal and **noise**; does **not increase link margin** by the full gain value.
+
+### 11. **Accounting for Noise**
+
+* **LNA Role**: Placed close to the antenna to reduce **cable loss** and **system noise**
+* **Adjustments**:
+
+  * Row 29: Cable Loss
+  * Row 30: Input Noise Temperature (Kelvin)
+
+### 12. **Noise Temperature Calculation**
+
+* **Noise Figure (NF)** to **Temperature**:
+
+  * NF = 0.2 dB → \~14 K
+  * Use [Noise Temp Calculator](https://www.pasternack.jp/t-calculatornoisefigure)
+  * Reference Temp: 290–300 K (room temperature)
+
+> Galactic noise in some directions can reach **\~200 K**. Use [this source](https://www.jstage.jst.go.jp/article/nictkenkyuhoukoku/6/22/6_23/_pdf) for reference.
+
+---
+
+## 🧮 Formulae & Notes (For Reference)
+
+* **Noise Temperature (T)** from NF:
+
+$$
+T = 290 \cdot \left(10^{\frac{NF}{10}} - 1\right)
+$$
+
+
+* **Effective Link Margin** is not linear with preamp gain due to noise figure influence
+
+---
+
+## 📁 Resources
+
+* 📄 `119_120_121_BIRDS-5 LinkMargin.xlsx`
+* 🔗 [Pasternack Noise Temp Calculator](https://www.pasternack.jp/t-calculatornoisefigure)
+* 🔗 [Galactic Noise Reference (J-STAGE)](https://www.jstage.jst.go.jp/article/nictkenkyuhoukoku/6/22/6_23/_pdf)
+* 🔗 [AQZ102 PhotoMOS Datasheet](https://www.digikey.com/en/products/detail/panasonic-electric-works/AQZ102/)
+