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UNUN 9:1 — HIGH-IMPEDANCE RANDOM WIRE MATCHING
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Purpose: Impedance transformation 450Ω unbalanced → 50Ω unbalanced
Type: Voltage transformer (3:1 turns ratio unun)
Insertion Loss: 0.15–0.25 dB (higher loss due to turns ratio)
Primary Use: High-impedance random wires, long-wire antennas

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CORE SPECIFICATIONS
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HF Configuration (160M–10M):
  Core: Single FT-240-43 (adequate for 9:1 unun)
  Material: Mix 43 (µ=850, AL=1100 µH/100T)
  Wire: #14 enameled copper
  Primary: 4 turns (antenna side, 450Ω)
  Secondary: 12 turns (coax side, 50Ω)
  Turns Ratio: 3:1 (gives 9:1 impedance transformation)
  Max Power: 400 W (higher loss than 4:1)
  Insertion Loss: 0.20–0.30 dB

Band-Specific Configuration:
  160M (1.8 MHz):   4 primary, 12 secondary (FT-240-43)
  80M (3.75 MHz):   4 primary, 12 secondary
  40M (7.15 MHz):   4 primary, 11 secondary (compromise)
  30M (10.1 MHz):   3 primary, 9 secondary (reduced turns)
  20M (14.2 MHz):   3 primary, 9 secondary
  10M (28.4 MHz):   3 primary, 9 secondary

Wire Lengths:
  Primary: ~60 inches (4 turns)
  Secondary: ~130 inches (12 turns)
  Total: ~190 inches

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IMPEDANCE TRANSFORMATION
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TURNS RATIO:
  N_ratio = 12 / 4 = 3:1
  Z_out = Z_in / N² = 450 / 9 = 50Ω ✓

VOLTAGE STEP-DOWN:
  V_out = V_in × (1/3) ≈ 0.33 × V_in

POWER CONSERVATION:
  P_in ≈ P_out (minus ferrite losses)
  High impedance → low current, low loss ideal

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FREQUENCY RESPONSE
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FT-240-43, 4:12 turns:

Frequency    Impedance Ratio    Insertion Loss
160M         9.2:1 (450→49)     0.30 dB
80M          8.9:1              0.25 dB
40M          8.5:1              0.20 dB
20M          8.2:1              0.15 dB
10M          7.8:1              0.12 dB

Notes:
  - Impedance ratio flat across HF band
  - Loss decreases at higher frequencies (ferrite loss drops)

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PRIMARY APPLICATIONS
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1. HIGH-IMPEDANCE RANDOM WIRES:
   - Wire feedpoint impedance 400–500Ω
   - Non-resonant long wire (>2λ length)
   - 9:1 unun essential for impedance matching

2. VERY LONG WIRES (300+ feet):
   - Extremely high impedance at some frequencies
   - 9:1 typical for broadband long-wire operation

3. END-FED LONG WIRES (without tuner):
   - Some long wires exhibit high impedance feedpoints
   - 9:1 converts directly to 50Ω (no tuner needed if impedance exact)

4. LOOP ANTENNAS:
   - Some loop designs have high-impedance feedpoints
   - 9:1 unun suitable if feedpoint impedance ~450Ω

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FAILURE MODES
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SYMPTOM: High SWR despite 450Ω antenna impedance
ROOT CAUSE: Antenna impedance changed (frequency dependent)
SOLUTION: Use tuner with 9:1 unun for broadband matching

SYMPTOM: Excessive heating
ROOT CAUSE: High loss (ferrite dissipating energy)
SOLUTION: Reduce power, or use larger core (FT-240-43×2)

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TESTING PROCEDURE
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Setup:
  Port 1: Coax output (50Ω)
  Port 2: Primary antenna connection (450Ω load)
  Use 450Ω resistive load for testing

Measurement 1 — Impedance Ratio (450Ω load):
  Sweep 1–30 MHz
  Expected: Z_out ≈ 50Ω
  S₁₁ <-20 dB

Measurement 2 — Insertion Loss:
  Sweep 1–30 MHz
  Expected: S₂₁ ≈ -0.15 to -0.25 dB
  Accept higher loss (expected for 9:1 ratio)

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DESIGN EQUATIONS
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Turns ratio for 450→50Ω:
  N_ratio = sqrt(450/50) = sqrt(9) = 3:1
  Use 4 primary, 12 secondary (3:1 ratio) ✓
  Or 3:9 (also 3:1 ratio) for higher frequencies

Insertion Loss:
  L_dB ≈ 0.1 + 0.003 × f_MHz (FT-240-43, 9:1)
  Example @ 14.2 MHz: L ≈ 0.14 dB

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POWER HANDLING
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FT-240-43 single core:
  Continuous (CW): 400 W @ 50°C ambient
  Peak (SSB): 600 W
  Thermal rise: ~20°C @ 400W (higher than 4:1)

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