satx

Building a DIY Satellite Antenna

Complete guides for building cost-effective satellite antennas.


1. VHF Turnstile Antenna (137 MHz - NOAA Weather Satellites)

Cost: ~$15-25
Difficulty: Easy
Performance: Excellent for NOAA APT reception

Materials Needed

Construction Steps

  1. Cut Elements:
    • Each dipole element: 53.4 cm (quarter wavelength at 137 MHz)
    • Cut 4 pieces of copper wire
  2. Prepare PVC Mast:
    • Drill hole for SO-239 connector at center
    • Drill 4 holes at 90° intervals for dipole elements
  3. Assemble Dipoles:
    • Create two dipoles perpendicular to each other
    • Phase one dipole 90° ahead using coax delay line
  4. Connect Feed:
    • Solder dipoles to SO-239 center and shield
    • Waterproof all connections

Detailed Guide


2. QFH Antenna (137 MHz - NOAA/METEOR)

Cost: ~$25-40
Difficulty: Moderate
Performance: Superior circular polarization, best for LEO

Materials Needed

Construction Steps

  1. Calculate Dimensions for 137.5 MHz:
    • Small loop circumference: 216.8 cm
    • Large loop circumference: 217.6 cm
    • Height: 54.4 cm
  2. Build Support Structure:
    • Use PVC pipes to create vertical supports
    • Space them at calculated loop diameter
  3. Form Loops:
    • Bend copper wire into helical loops
    • Small loop: 2 turns
    • Large loop: 2 turns, slightly larger diameter
  4. Phase and Connect:
    • Connect loops with 90° phase difference
    • Use balun to match impedance

Detailed Guides


3. UHF Yagi Antenna (435-438 MHz - CubeSats)

Cost: ~$30-50
Difficulty: Moderate
Performance: High gain, directional (requires tracking)

Materials Needed

Construction Steps

  1. Calculate Element Lengths (435 MHz):
    • Reflector: 35.8 cm
    • Driven element: 32.6 cm (dipole)
    • Director 1: 31.2 cm
    • Director 2: 30.5 cm
    • Director 3: 30.0 cm
  2. Element Spacing:
    • Reflector to driven: 16.5 cm
    • Driven to director 1: 15.0 cm
    • Directors spaced: 12-15 cm apart
  3. Assembly:
    • Drill holes in PVC boom for elements
    • Insert and secure elements
    • Connect driven element to SO-239
    • Isolate driven element from boom
  4. Tuning:
    • Use antenna analyzer or SWR meter
    • Adjust element lengths for minimum SWR

Detailed Guide


4. Helical Antenna (2.4 GHz - S-band Satellites)

Cost: ~$40-60
Difficulty: Advanced
Performance: Circular polarization, high gain

Materials Needed

Construction Steps

  1. Calculate Helix Dimensions (2.4 GHz):
    • Circumference: 12.5 cm (1λ)
    • Pitch: 3.125 cm (0.25λ)
    • Number of turns: 10-12
    • Diameter: 4 cm
  2. Wind Helix:
    • Mark PVC pipe with spiral guide
    • Wrap copper wire following marks
    • Secure with epoxy or hot glue
  3. Ground Plane:
    • Cut circular reflector
    • Mount at base of helix
    • Connect N-connector
  4. Feed Point:
    • Connect helix start to center conductor
    • Ground plane to shield

Detailed Guide


5. Eggbeater Antenna (145/435 MHz - Dual-band LEO)

Cost: ~$35-50
Difficulty: Moderate-Advanced
Performance: Dual-band, circular polarization, omnidirectional

Materials Needed

Construction Steps

  1. VHF Elements (145 MHz):
    • Loop circumference: 207 cm
    • Height: 51.8 cm
  2. UHF Elements (435 MHz):
    • Loop circumference: 69 cm
    • Height: 17.3 cm
  3. Nested Construction:
    • Mount UHF loops inside VHF loops
    • Use separate feed points
    • Maintain 90° phase offset for each band
  4. Tuning:
    • Test each band independently
    • Adjust loop sizes for resonance

Detailed Guide


Antenna Testing and Tuning

Equipment Needed

Testing Procedure

  1. SWR Measurement:
    • Connect antenna to analyzer
    • Sweep frequency band
    • Target SWR < 2:1 at center frequency
  2. Pattern Testing:
    • Use known satellite pass
    • Compare signal strength vs. time
    • Verify omnidirectional or directional pattern
  3. Tuning:
    • Adjust element lengths for minimum SWR
    • Trim in small increments (1-2mm)
    • Retest after each adjustment

Antenna Mounting

Weatherproofing

Mounting Hardware

Positioning


Performance Comparison

Antenna Frequency Gain Pattern Difficulty Cost
Dipole VHF/UHF 2 dBi Omni Easy $10
Turnstile 137 MHz 3 dBi Omni Easy $20
QFH 137 MHz 4 dBi Omni (CP) Moderate $35
Yagi UHF 10+ dBi Directional Moderate $45
Eggbeater Dual-band 5 dBi Omni (CP) Advanced $50
Helix S-band 12+ dBi Directional Advanced $60

CP = Circular Polarization


For beginners: Start with a VHF Turnstile or QFH

For intermediate: Add a UHF Yagi


Safety Notes


Resources

Online Calculators

Communities

Suppliers


Build once, receive forever!