Skip to content

README.md

Latest commit

 

History

History
161 lines (117 loc) · 6.35 KB

README.md

File metadata and controls

161 lines (117 loc) · 6.35 KB
Raw

Mergen-21 Logo

Mergen-21: Low-Cost 21 cm Hydrogen Line Radio Telescope

A radio telescope I built for my EE401 graduation project at Ozyegin University. It listens at 1420.405 MHz — the hydrogen line — and I used it to map how fast different parts of the Milky Way are rotating.

Science goal: Galactic rotation curve via the tangent-point method, observed from Istanbul, Turkey.

System Overview

RF System Block Diagram

Antenna mounted for first-light observations

Antenna

  • Type: Pyramidal horn, 1.5 mm aluminum sheet, laser-cut & riveted
  • Design frequency: 1420.405 MHz (HI 21 cm line)
  • Measured S11: -42 dB @ 1.4204 GHz (exceeded simulation by a lot)
  • Simulated S11: ~-30 dB near 1.40 GHz (CST Studio Suite)
  • Directivity: 16.9 dBi at 1.42 GHz
  • 3 dB beamwidth: 22.0° (H-plane), 25.2° (E-plane)

RF Chain

Stage Component Function Gain (dB) NF (dB) OIP3 (dBm)
1 ZX60-P162LN+ LNA 19.7 0.7 +29.8
2 ZX75BP-1450-S+ Bandpass filter (~50 MHz passband @ 1450 MHz) -0.8 0.8 N/A
3 ZX60-V63+ Second amplifier 20.8 3.7 +32.2
Cascade LNA + BPF + Amp 39.7 (meas.) 0.75 (meas.) +29.5 (meas.)

Backend

  • SDR: ADALM-PLUTO
  • Software: GNU Radio for signal acquisition
  • Analysis: Python (NumPy, SciPy, Matplotlib, Astropy)

Here's what the GNU Radio receiver flowgraph looks like:

GNU Radio receiver flowgraph

Mechanical

  • Horn antenna from laser-cut aluminum sheet metal
  • Waveguide-to-coax transition with N-type connector
  • A 3D-printed tripod adapter was designed (files in hardware/antenna/3d-print/) but the mount did not work out in practice and wasn't used for observations

Project Status

Component Status Notes
Hardware (antenna, RF chain, LDO) Complete Fully characterized; measurement data available
Power supply board Complete Gerbers ready; BOM in hardware/ldo-regulator/bom.pdf
Simulations (CST, AWR) Complete Exported results in hardware/simulation/
Measurements (VNA, IP3, NF) Complete 39.7 dB gain, 0.75 dB NF, OIP3 +29.5 dBm (cascade)
GNU Radio flowgraphs Complete reciver.grc (main) + 21cm synth/ test flowgraphs
Analysis software In Progress Waterfall viewer done; full calibration pipeline in development
First-light observations Complete Directional sweeps 2026-04-29; data in observations/data/
Open-source release In Progress Final cleanup underway

Key Results

RF Receiver

  • Cascade gain: 39.7 dB (measured @ 1.42 GHz via ZNB8)
  • Cascade NF: 0.75 dB (measured; agrees with theory to 0.19 dB)
  • Cascade OIP3: +29.54 dBm (-12 dBm tone input; TOI spread 0.3 dB)
  • Measurements traceable to R&S ZNB8 VNA & FSVA3044 spectrum analyzer

Antenna

  • Measured S11: -42 dB @ 1.4204 GHz
  • Simulated directivity: 16.9 dBi
  • 3 dB beamwidth: ~23° (H-plane & E-plane similar due to square waveguide)
  • Material: 1.5 mm aluminum sheet, laser-cut

System Sensitivity

  • System temperature: ~30–40 K (sky + ground + receiver near zenith)
  • MDS: ~-150 dBm @ 1 MHz BW (conservative)

Repository Structure

mergen-21/
├── hardware/                    # All hardware (antenna, RF chain, power, sims)
│   ├── antenna/                 # Horn: CAD, drawings, DXF, STL, photos
│   ├── rf-chain/                # Component datasheets & S-parameters
│   ├── ldo-regulator/           # Dual LDO board (Altium, Gerbers, BOM, STEP)
│   └── simulation/              # CST antenna sims & AWR cascade analysis
├── measurements/                # Lab characterization data
│   ├── rf-chain/vna/            # VNA S-parameters (R&S ZNB8)
│   ├── rf-chain/ip3/            # IP3 / intermodulation
│   ├── rf-chain/nf/             # Noise figure
│   └── antenna/                 # Horn S11 & manufacturing notes
├── software/                    # Data acquisition & analysis
│   ├── gnuradio/                # GNU Radio flowgraphs (.grc)
│   └── analysis/                # Python scripts (waterfall viewer, etc.)
├── observations/                # First-light data & plots (2026-04-29)
│   ├── data/                    # Raw spectra (.dat, NumPy float32)
│   └── plots/                   # Waterfall & sweep plots
└── docs/                        # Build log, status, diagrams

Quick Navigation

Getting Started

git clone https://github.com/AlpGoXd/mergen-21.git
cd mergen-21
pip install -r software/requirements.txt

Dependencies:

  • GNU Radio 3.10+ with PlutoSDR block (gr-iio)
  • Python 3.8+ — numpy, scipy, matplotlib, astropy

CST, AWR, and Autodesk Inventor are only needed to re-run simulations or edit CAD. All exported results (S-parameters, STEP, Gerbers, PDFs) are already in the repo.

Observation Site

  • Location: Istanbul, Turkey (~41.0°N, 29.0°E)
  • Target: Galactic plane HI emission at various galactic longitudes
  • Method: Tangent-point method for rotation curve extraction

Licensing

Why "Mergen"?

Mergen is a figure from Turkic mythology — associated with wisdom, precision, and skilled targeting. Felt like the right name for a telescope.

Acknowledgments

Author

Alp Gokalp — Electrical & Electronics Engineering, Ozyegin University (Class of 2026)