TECHNICAL MANUAL

RF HYBRID COUPLERS AND POWER DIVIDERS

Model TM-HYB-001 — Revision A

All Amateur Radio Bands, 160M – 23cm

LIST OF EFFECTIVE PAGES

CHAPTER 1 — GENERAL INFORMATION

1.1 Scope

This manual provides design, construction, operating, and test instructions for the TM-HYB-001 family of RF hybrid couplers and power dividers. Designs cover all amateur radio bands from 160 meters through 23 centimeters (1.85 MHz through 1296 MHz) and are intended for phased array feed networks, circular polarization feeds, antenna switching, and power combining/splitting applications.

The following designs are documented:

1.2 Specifications Summary

1.3 Definitions

Hybrid coupler: A 4-port network that divides power between two output ports with a controlled phase difference.

Power divider: A 3-port network that divides power between two or more output ports with controlled amplitude ratio and phase relationship.

Isolation: The attenuation between two output ports of a divider. High isolation means a mismatch at one port does not affect the other.

Phase balance: The difference in electrical phase between two output ports. For a quadrature hybrid, the target is 90°. For a Wilkinson, the target is 0°.

Amplitude balance: The difference in signal level (dB) between two output ports. Target: 0 dB (equal split).

Return loss: 20 × log₁₀(|Γ|) in dB. A well-matched port shows >20 dB return loss (|Γ| < 0.1, SWR < 1.22:1).

CHAPTER 2 — TECHNICAL DESCRIPTION

2.1 Wilkinson Power Divider Theory

The Wilkinson power divider (1960) achieves simultaneous port matching and output isolation through two λ/4 transmission line sections and a bridging resistor.

Design equations (2-way, equal split):

Quarter-wave arm impedance: Z_λ/4 = Z0 × √2 = 70.71 Ω   (for Z0 = 50 Ω)
Isolation resistor:          R_iso = 2 × Z0 = 100 Ω
Split ratio:                  −3.01 dB (equal)

S-matrix (ideal, at design frequency):

       [  0      -j/√2   -j/√2 ]
[S] =  [-j/√2    0        0   ]
       [-j/√2    0        0   ]

Port 1 is the input; Ports 2 and 3 are the equal-amplitude, in-phase outputs. The isolation resistor (100 Ω between ports 2 and 3) only dissipates power when ports 2 and 3 are presented with unequal loads. Under matched conditions, it carries no current.

Bandwidth: The Wilkinson’s 3 dB bandwidth is approximately 70% to 150% of the design frequency (2.1:1 ratio) for <1 dB amplitude ripple. Multi-section designs extend this to 4:1 or greater.

Lumped-element substitute for λ/4 section (low-pass T-network):

               L/2            L/2
IN ────┤▬▬▬├──────┬──────┤▬▬▬├──── OUT
                 [C]
                  │
                 GND

L = Z_arm / (2π × f₀)       [Henrys, Z in Ohms, f in Hz]
C = 1 / (2π × f₀ × Z_arm)   [Farads]

This single-section approximation gives ±5° phase error and ±0.5 dB amplitude error over approximately ±40% of center frequency.

2.2 Quadrature (90°) Hybrid — Branch-Line Coupler

The branch-line coupler consists of four λ/4 sections arranged in a square, with ports at each corner.

Port definitions:

Standard convention: Phase of Port 3 lags Port 2 by 90°.

Design equations:

Shunt arm (vertical) impedance:  Z_sh = Z0 = 50 Ω
Series arm (horizontal) impedance: Z_sr = Z0 / √2 = 35.35 Ω
All arms: λ/4 at design frequency

S-matrix (ideal):

       [  0    -j/√2   -1/√2   0   ]
[S] =  [-j/√2   0       0    -1/√2 ]
       [-1/√2   0       0     j/√2 ]
       [  0    -1/√2   j/√2    0   ]

The 90° phase difference between Port 2 (Through) and Port 3 (Coupled) makes this network ideal for:

• Circular polarization feeds: Connect Port 2 to one linear element and Port 3 to the orthogonal element. Equal amplitudes with 90° phase difference produce circular polarization.
• Phased array endfire elements: Two λ/4-spaced elements with 90° phase shift produce a cardioid (unidirectional) pattern with ≈5 dB F/B ratio.
• I/Q mixing: The 90° channel is the I path; the 0° channel is the Q path.

2.3 Rat-Race (180°) Hybrid

The rat-race (ring) coupler consists of a single transmission line ring of 3λ/2 circumference, with four ports connected at λ/4 intervals.

Key dimensions:

Ring characteristic impedance: Z_ring = Z0 × √2 = 70.71 Ω
Total ring length:              3λ/2
Port spacing:  P1→P3 = λ/4,  P3→P2 = λ/4,  P2→P4 = λ/4,  P4→P1 = 3λ/4

Operation:

Phased array application (2-element):

• Drive P1 (Σ): both antennas in-phase → broadside radiation
• Drive P2 (Δ): antennas 180° out of phase → endfire radiation (null at broadside, two endfire lobes)
• Switch between P1 and P2 for switchable pattern diversity

Monopulse DF (direction finding):

• Connect two antennas to P3 and P4
• P1 (Σ): maximum signal in boresight direction → tracking
• P2 (Δ): null at boresight, proportional to angular error → steering

2.4 Transmission Line Transformers (TLT)

TLTs exploit the transmission-line mode (as opposed to transformer flux) for bandwidth. The transmission line passes differential-mode signals unchanged while the core suppresses common-mode (choking action).

Key principle: The core does not transform voltage or current. It provides high impedance to common-mode currents, forcing all current to flow as differential mode through the line. This gives decade-wide bandwidth.

Guanella balun (1:1): A single coaxial or bifilar pair wound on a ferrite core. Converts unbalanced (coax) to balanced (dipole/balanced line) feed. Common-mode impedance: >500 Ω across 1–30 MHz with 6 turns on BN-43-202.

Guanella 4:1 balun: Two 1:1 sections in series at balanced (200 Ω) end, in parallel at unbalanced (50 Ω) end. Voltage across each line = V/2; current doubles; impedance ratio = 4:1.

Ruthroff 4:1 unun: Voltage-addition type. Input voltage appears at both primary and secondary ends; output = 2V, output impedance = Z_in/4. Narrower bandwidth than Guanella (limited by propagation delay through line).

2.5 Circular Polarization Feed

For a phased array or single antenna requiring circular polarization:

             ┌─────────────────────────────────────┐
    RF in ───┤  90° Hybrid Coupler (Branch-Line)   │
             │   Port 1 → Input                     │
             │   Port 2 → Element A (0°)             ├──→ Element A (horizontal)
             │   Port 3 → Element B (−90°)           ├──→ Element B (vertical)
             │   Port 4 → 50Ω load (isolated)       │
             └─────────────────────────────────────┘

RHCP (Right-Hand Circular):  Element A=0°,  Element B=−90°
LHCP (Left-Hand Circular):   Element A=0°,  Element B=+90°  (swap P2/P3)

Axial ratio (quality of circular polarization):

AR (dB) = 20 × log₁₀ [ tan(45° + ε_phase/2) ]    (ε_phase = phase error in degrees)
AR (dB) ≈ 20 × log₁₀ [ (1 + δ_amp) / (1 − δ_amp) ]   (δ_amp = amplitude error ratio)

For AR < 1.5 dB: phase error < 5°, amplitude error < 0.5 dB. For AR < 3 dB: phase error < 10°, amplitude error < 1 dB.

CHAPTER 3 — OPERATING INSTRUCTIONS

3.1 Initial Setup and Connections

WARNING: Do not connect any port to a transmitter without first verifying the hybrid is terminated in 50 Ω at all ports. An open or short at any port will appear as a partial mismatch at the input and may damage the transmitter or the hybrid’s resistors.

CAUTION: Never exceed the power rating of the isolation resistors. At HF (100 W input), use 2 W resistors. At VHF/UHF, 0.5 W SMD resistors are adequate for up to 25 W.

Initial setup procedure:

1. Terminate all output ports in matched 50 Ω loads (SMA or BNC terminations).
2. With an RF source (QRP transmitter at low power, or signal generator), apply a signal to Port 1 (input).
3. Measure signal level at each output port with a power meter or calibrated receiver.
4. Verify amplitude balance: outputs should be equal within 0.5 dB.
5. Proceed to Chapter 4 for phase verification.

3.2 Wilkinson Divider — Operation

Power dividing (1 to 2): - Port 1: RF input - Ports 2 and 3: equal-power outputs; load both with 50 Ω antennas or stages - Each output receives −3 dB (half the input power)

Power combining (2 to 1): - Ports 2 and 3: input signals (must be coherent — same frequency and phase) - Port 1: combined output (−3 dB per input port) - The isolation resistor absorbs any power difference between inputs

NOTE: For power combining, the two input signals must be coherent (in-phase, within ±5°). If signals are out of phase, the isolation resistor absorbs the mismatch power. At 180° phase difference, all power is absorbed by the resistor and no output appears at Port 1.

3.3 Quadrature Hybrid — Operation

Circular polarization feed: 1. Connect Port 1 to the RF source (transceiver or power amplifier). 2. Connect Port 2 (0° output) to one linear polarization element. 3. Connect Port 3 (−90° output) to the orthogonal element. 4. Connect Port 4 to a 50 Ω termination. 5. Verify axial ratio per Chapter 4 procedure.

Switchable polarization: - RHCP: Port 2 → Horizontal element, Port 3 → Vertical element - LHCP: Port 3 → Horizontal element, Port 2 → Vertical element - Use a DPDT relay or manual switch to swap P2/P3 connections

2-element endfire phased array: 1. Connect Port 1 to RF source. 2. Port 2 (0°): Element 1 (rear element for +X endfire). 3. Port 3 (−90°): Element 2 (front element, λ/4 spacing toward +X). 4. Port 4: 50 Ω load. 5. Endfire direction: toward Element 2 (+X axis).

3.4 Rat-Race Hybrid — Operation

2-element phased array (switchable broadside/endfire): 1. Antennas connected to Ports 3 and 4 (the two driven ports). 2. Drive Port 1 (Σ): Both antennas in-phase → broadside radiation. 3. Drive Port 2 (Δ): Antennas 180° out-of-phase → endfire radiation. 4. Terminate unused port (Σ or Δ) in 50 Ω when driving the other.

Direction-finding (monopulse): 1. Antennas to Ports 3 and 4. 2. Port 1 (Σ) → receiver channel A: sum signal. 3. Port 2 (Δ) → receiver channel B: difference signal. 4. Bearing: signal is maximum on channel A when beam is on target. 5. Null on channel B confirms boresight.

3.5 Band Switching (HF Lumped-Element Version)

The band-switched lumped-element Wilkinson has dual rotary switches (SW1, SW2) on the lid for selecting the inductor and capacitor values.

Procedure: 1. Identify operating band. 2. Set SW1 (inductor switch) to the position labeled for that band. 3. Set SW2 (capacitor switch) to the matching position.

NOTE: Both switches must be on the same position (same band) at all times. Operating with mismatched switch positions will result in incorrect phase and amplitude, potentially damaging connected equipment.

4. Verify match with antenna analyzer before applying transmit power.

CHAPTER 4 — PHASE AND AMPLITUDE BALANCE MEASUREMENT

4.1 Overview

Phase and amplitude balance measurement verifies that the hybrid coupler is performing to specification. Two methods are described:

• Method A — Using the CYD monitor (firmware/hybrid_monitor_cyd.ino)
• Method B — Using general-purpose instruments (VNA, oscilloscope, spectrum analyzer)

4.2 Method A — CYD Hybrid Monitor

The CYD firmware measures amplitude balance using two AD8307 log detectors and phase balance using zero-crossing time measurement.

Required hardware: - CYD (ESP32-2432S028) with hybrid_monitor_cyd.ino firmware loaded - Two AD8307 log detector modules (one per output port) - Signal source at band center frequency, −20 to 0 dBm

Connection:

  Signal source ──── Port 1 (input) of hybrid under test

  Port 2 output ──── AD8307 module #1 ──── CYD GPIO36 (ADC1)
  Port 3 output ──── AD8307 module #2 ──── CYD GPIO39 (ADC1)

  Port 2 output ──── (after resistive divider) ──── CYD GPIO34 (zero-crossing)
  Port 3 output ──── (after resistive divider) ──── CYD GPIO35 (zero-crossing)

  Isolated port (Port 4) ──── 50 Ω termination

Procedure:

1. Flash hybrid_monitor_cyd.ino to CYD.
2. Connect hardware as shown above.
3. Apply power. CYD startup screen shows “HYB-001 Monitor”.
4. Touch BAND tab. Select band under test and hybrid type (WILKINSON / QUADRATURE 90° / RAT-RACE 180°).
5. Touch LEVEL tab. Verify both AD8307 readings appear. Amplitude balance (ΔAmp) is displayed in dB.
6. Touch PHASE tab. Verify phase angle is displayed. Phase error vs. target is shown in green (PASS) or red (FAIL).
7. Record readings. Touch HIST tab to view statistics after multiple measurements.
8. Touch SPEC tab to configure pass/fail limits and view GO/NO-GO result.

Expected readings (at design frequency):

4.3 Method B — VNA or Network Analyzer

A 2-port VNA (such as NanoVNA or miniVNA Tiny) can measure phase and amplitude at each port relative to Port 1.

Procedure (2-port VNA, S21 measurement):

1. Calibrate VNA (SOL at Port 1, Open at Port 2).
2. Connect VNA Port 1 to hybrid input (Port 1 of DUT).
3. Terminate hybrid’s isolated port (Port 4 for quadrature hybrid) in 50 Ω.
4. Connect VNA Port 2 to hybrid Port 2 (through output).
5. Sweep frequency through design band.
6. Record: |S21| (amplitude) and ∠S21 (phase) at design frequency.
7. Move VNA Port 2 to hybrid Port 3 (coupled output).
8. Record: |S21| and ∠S21.
9. Amplitude balance = |S21 at P2| − |S21 at P3| in dB.
10. Phase balance = ∠S21 at P2 − ∠S21 at P3 in degrees.

Expected S21 values:

NOTE: Absolute phase values depend on measurement cable lengths and calibration. Only the relative phase difference between ports is meaningful in these measurements.

4.4 Method C — Oscilloscope (Two-Channel)

For frequencies below 50 MHz, a dual-channel oscilloscope can directly display the phase difference.

Procedure:

1. Apply a 1 Vpeak sine wave at band center frequency to hybrid Port 1.
2. Connect oscilloscope Channel 1 to Port 2; Channel 2 to Port 3.
3. Terminate all unused ports in 50 Ω.
4. Set oscilloscope to display both channels at same scale.
5. Verify amplitude balance: channels should be equal amplitude.
6. Use oscilloscope cursors to measure time difference between zero crossings of Channel 1 and Channel 2.
7. Phase difference = (Δt / T) × 360° where T = 1/f₀.

Example (40M, 7.150 MHz, 90° hybrid):

  T = 1 / 7.150 MHz = 139.9 ns
  Expected Δt (90°): 139.9 / 4 = 35.0 ns
  Acceptable range: 31.4–38.6 ns (±5°)

4.5 Return Loss (Port Match) Measurement

IMPORTANT: Return loss must be measured with all other ports terminated. An unterminated port causes reflections that make the measurement invalid.

Using NanoVNA (S11 measurement):

1. Calibrate NanoVNA with SOLT (Short-Open-Load-Through).
2. Terminate hybrid Ports 2, 3 (and 4 if applicable) in 50 Ω loads.
3. Connect NanoVNA CH0 to hybrid Port 1.
4. Measure S11 (return loss) across frequency band.
5. Acceptance criterion: S11 < −20 dB at design frequency.

Using directional coupler bridge: See Chapter 3 of TM-FC-001 (frequency counter manual) for SWR bridge construction. Place bridge between source and hybrid Port 1. Null indicates perfect match (SWR = 1.0:1).

4.6 Isolation Measurement

Procedure:

1. Connect signal source to Port 2.
2. Terminate Port 1 and Port 4 (if applicable) in 50 Ω.
3. Measure power at Port 3 (the isolated port).
4. Isolation (dB) = P_in(dBm) − P_at_P3(dBm).
5. Acceptance criterion: Isolation > 20 dB.

Typical results: - At design frequency: 25–35 dB (excellent) - At ±20% of design frequency: 15–20 dB (adequate) - At 2× design frequency: 8–12 dB (significant leakage — use LP filter)

4.7 Phase and Amplitude Balance Record Sheet

Copy this table for field measurements:

TM-HYB-001 BALANCE MEASUREMENT LOG

Date: ____________  Operator: ____________  Band: ____________
Hybrid type: [ ] Wilkinson  [ ] Quadrature  [ ] Rat-race
Frequency: ____________ MHz  Signal level at Port 1: ________ dBm

AMPLITUDE BALANCE:
  Port 2 level: ________ dBm
  Port 3 level: ________ dBm
  ΔAmp (P2−P3): ________ dB   Spec: ±0.3 dB   [ ] PASS  [ ] FAIL

PHASE BALANCE:
  Phase at Port 2: ________ °
  Phase at Port 3: ________ °
  Phase difference: ________ °   Target: ________ °
  Phase error: ________ °        Spec: ±5°       [ ] PASS  [ ] FAIL

RETURN LOSS:
  Port 1 S11: ________ dB   Spec: <−20 dB   [ ] PASS  [ ] FAIL
  Port 2 S11: ________ dB                   [ ] PASS  [ ] FAIL
  Port 3 S11: ________ dB                   [ ] PASS  [ ] FAIL

ISOLATION:
  Port 2 → Port 3: ________ dB   Spec: >20 dB   [ ] PASS  [ ] FAIL

REMARKS: _______________________________________________

CHAPTER 5 — CONSTRUCTION PROCEDURES

5.1 General Construction Guidelines

Component quality: - Use NP0/C0G capacitors for all RF applications. X7R and Y5V dielectrics have value shifts with temperature and voltage that degrade performance. - Use ±5% capacitors as minimum tolerance. ±1% for VHF/UHF. - Wind all inductors on cores of correct permeability for the band. Measure finished inductors with an LC meter before installation. - Use E96 resistors (1%) for isolation resistors. 0.5 W for up to 25 W RF power; 2 W for up to 100 W.

PCB construction: - HF (through 30 MHz): Perfboard or Manhattan-style construction is adequate. Keep leads as short as possible. Star-ground at circuit center. - VHF (50–200 MHz): Use double-sided FR-4. Continuous ground plane on bottom. Short component leads (< 5 mm). - UHF (200 MHz+): Microstrip PCB construction required. Use 50 Ω trace width on FR-4 (h=1.6 mm): w ≈ 2.9 mm for 50 Ω. Controlled impedance board recommended for 23 cm and above.

5.2 Toroid Winding Procedure (HF Inductors)

1. Measure core OD. Use appropriate wire gauge (see parts list).
2. Thread wire through core hole. First pass through counts as one turn.
3. Wind evenly distributed around circumference (not bunched).
4. Leave 30 mm leads at each end.
5. Measure inductance with LC meter after winding.
6. Adjust turns as needed:
   • Too high by X%: Remove √X% of turns (inductance ∝ N²).
   • Too low by X%: Add √X% of turns.
7. Secure winding with one drop of nail varnish or varnish at two points.
8. Trim leads to 10 mm.

Target tolerance: ±3% of design value.

5.3 Coaxial λ/4 Section Construction (VHF/UHF)

1. Calculate physical length:

   length_mm = (c × VF / (4 × f)) × 1000

   Where VF = velocity factor (0.66 for RG-58/RG-59; 0.70 for PTFE; 1.0 for air-spaced line).

2. Cut coax longer than calculated by 5 mm.

3. Install SMA or BNC connectors on both ends.

4. Trim in steps of 1–2 mm, measuring electrical length with VNA (S11 phase response) until the section is exactly 90° (λ/4) at design frequency.

5. Seal both ends with heat-shrink tubing after final trim.

CAUTION: Cutting is irreversible. Always start long and trim toward the target length.

5.4 Microstrip Hybrid Construction (UHF)

1. Print PCB with controlled impedance (specify to fab if ordering). Alternatively, etch at home: use photoresist or toner transfer.

2. Trace widths:

   • 50 Ω on FR-4 (h=1.6 mm, εr=4.4): w = 2.9 mm
   • 35.35 Ω on FR-4: w = 5.2 mm
   • 70.71 Ω on FR-4: w = 0.9 mm

3. Verify trace widths with Saturn PCB Toolkit or AppCAD before ordering.

4. Solder SMA edge-launch connectors at each port. Keep solder joints small; excess solder creates capacitive discontinuities at UHF.

5. Mount isolation resistors (for Wilkinson) as close as possible to the output junction pads. For >500 MHz, use 0402 SMD MELF resistors.

5.5 Weatherproofing Procedure

For outdoor (mast-head) installation, all hybrid enclosures must be weatherproofed before deployment.

1. Apply conformal coating (Humiseal 1B31 or equivalent) to all PCB surfaces after testing is complete and verified. Apply 2 coats.

2. Allow 24 hours cure time at room temperature.

3. Install completed PCB in ASA enclosure (openscad/enclosure_hybrid_hf.scad or enclosure_hybrid_vhf.scad).

4. Install O-ring in lid groove. O-ring should protrude 0.3 mm above groove face when uncompressed.

5. Torque lid screws uniformly. M3 screws: 0.5 N·m (5 in-lbf). M4 screws: 1.0 N·m (9 in-lbf). Do not overtighten (cracks ASA).

6. Apply self-amalgamating (self-fusing) tape over all SMA/BNC connector bodies and coaxial cable entry points. At least 2 layers.

7. Apply silicone sealant around cable gland entry.

8. Label box with: band, hybrid type, date of construction, and port ID.

CHAPTER 6 — EZNEC/NEC PHASED ARRAY MODELING

6.1 Overview of NEC Model Files

Three NEC model files are provided in the nec_models/ directory:

6.2 Running NEC Models

With 4nec2 (Windows, free):

1. Open 4nec2 application.
2. File → Open → select .nec file.
3. Run → Calculate.
4. View → Far Field Plot for radiation patterns.
5. View → Currents for element current distribution.
6. View → Impedance at feed points.

With EZNEC (Windows, paid — EZNEC Pro/2 or EZNEC+):

1. Open EZNEC.
2. File → Open NEC file (some syntax differences may require conversion).
3. Run Frequency Sweep to see pattern vs. frequency.
4. Patterns → 3D Pattern for full visualization.

With PyNEC (Python, cross-platform):

import PyNEC
c = PyNEC.nec_context()
c.geometry_complete(0)    # GE
c.gn_card(2, 0, 0, 0, 13.0, 0.005, 0, 0)  # GN
# Load GW, EX, FR, RP cards from .nec file
# See PyNEC documentation for card mapping

With xnec2c (Linux):

xnec2c phased_2el_endfire_20m.nec

6.3 Interpreting NEC Output

Gain: Shown in dBi (isotropic) or dBd (over dipole; dBd = dBi − 2.15 dB). The pattern shows gain vs. azimuth and elevation angle.

F/B ratio: Maximum forward gain minus rearward gain at 180° from the main lobe. Read at the same elevation angle.

Feed impedance: NEC reports complex impedance Z = R + jX at each feed point. For a phased array with mutual coupling, impedance may differ significantly from a free-space single element. A matching network may be required.

Current forcing: A quadrature hybrid or Wilkinson divider enforces equal currents regardless of element self-impedance changes from mutual coupling. This is the key practical advantage of these networks over simple L-C phasing: the hybrid’s port isolation prevents mutual coupling from affecting the feed currents.

6.4 Modifying NEC Models for Other Bands

To adapt the 20M model to another band, scale all dimensions by f₂₀/f_target:

scale_factor = 14.175 / f_target_MHz

New element length = 10.470 × scale_factor   (meters)
New element spacing = 5.292 × scale_factor   (meters)
New height = 10.0 × scale_factor             (meters, optional)

For the 40M version (7.150 MHz): scale_factor = 14.175/7.15 = 1.982 - Element length: 10.470 × 1.982 = 20.75 m (half-wave) - Element spacing: 5.292 × 1.982 = 10.49 m (λ/4)

6.5 4-Element Square Array — Phasing Network

The phased_4el_square_20m.nec model uses sequential phasing:

Element 1:   0°  → direct feed (reference)
Element 2: −90°  → one all-pass section
Element 3: −180° → two all-pass sections  (or reverse-polarity feed)
Element 4: −270° → three all-pass sections (or +90° directly)

All-pass 90° section for 14.175 MHz (from §2.4 of sch_lumped_element_hf.txt):

Connect in series: source → L → node → C to GND → 50 Ω load. Phase shift: −90° at 14.175 MHz, ±10° from 8–25 MHz.

CHAPTER 7 — MAINTENANCE

7.1 Routine Maintenance Schedule

7.2 Connector Maintenance

SMA connectors: - Inspect center pin for straightness. A bent center pin causes VSWR degradation. - Apply a small amount of Dow Corning 111 compound or PTFE lubricant to threads before assembly. This prevents galling and ensures waterproof seal. - Torque: hand-tight + ¼ turn with wrench. Do not use pliers directly on the connector hex.

BNC connectors: - Inspect bayonet pins for wear. A worn bayonet allows connector to rotate, causing intermittent contact. - Replace BNC if bayonet is loose.

7.3 O-Ring Replacement

1. Remove lid screws. Carefully pry lid from box body.
2. Remove old O-ring. Clean groove with isopropyl alcohol.
3. Measure O-ring groove dimensions: width and depth.
4. Order replacement O-ring: 2 mm cross-section, continuous loop matching groove perimeter. Use EPDM or silicone material (UV resistant).
5. Apply thin coat of silicone grease to new O-ring.
6. Seat O-ring in groove without twisting.
7. Reinstall lid; check O-ring protrusion before final tightening.

CHAPTER 8 — TROUBLESHOOTING

8.1 High Insertion Loss (>3.5 dB)

8.2 Poor Amplitude Balance (>0.5 dB)

8.3 Phase Error (>5°)

8.4 Poor Isolation (<15 dB)

8.5 Hybrid Works at Test, Fails Outdoors

CHAPTER 9 — PARTS LIST

9.1 2-Way Wilkinson Divider — HF (One Unit)

9.2 4-Way Wilkinson Divider — HF (One Unit)

9.3 Quadrature Hybrid — HF (One Unit)

9.4 Rat-Race Coupler — VHF/UHF (One Unit)

9.5 TLT Balun — HF (Guanella 1:1, One Unit)

9.6 CYD Monitor — Hybrid Test System

9.7 Enclosure Components

APPENDIX A — COMPLETE COMPONENT VALUE TABLES

A.1 Wilkinson 2-Way — All Bands

For 50 Ω system; Z_arm = 70.71 Ω; T-network (L/2, C, L/2); R_iso = 100 Ω. L = 70.71/(2πf), C = 1/(2πf × 70.71)

A.2 Quadrature Hybrid — All Bands

L_sh = 50/(2πf), C_sh = 1/(2πf×50), L_sr = 35.35/(2πf), C_sr = 1/(2πf×35.35)

APPENDIX B — TRANSMISSION LINE LENGTH TABLES

B.1 λ/4 Coaxial Sections (50 Ω, RG-58, VF=0.66)

Length (mm) = 49,500 / f_MHz

B.2 Rat-Race Ring (3λ/2, RG-59, VF=0.66)

Total length = 3 × (λ/4 × 4) × VF / 4 = 3 × (c×VF)/(4f) × … = 3×49500/f_MHz mm

APPENDIX C — NEC MODEL QUICK REFERENCE

C.1 NEC Card Summary for Phased Arrays

GW  wire geometry (tag, segs, x1,y1,z1, x2,y2,z2, radius)
GE  geometry end (0=free space, 1=ground present)
GN  ground parameters (type, -, -, -, εr, σ_Sm, -, -)
EX  excitation (0=voltage, tag, seg, 0, re(V), im(V))
FR  frequency (0=single, 0, 0, 0, f_MHz, 0)
RP  radiation pattern (0=gain, θ_pts, φ_pts, mode, θ0, φ0, Δθ, Δφ)
EN  end of model

C.2 Phase Encoding for EX Card

APPENDIX D — WEATHERPROOFING AND FIELD INSTALLATION

D.1 Outdoor Installation Checklist

[ ] Conformal coat applied (2 coats); cure complete
[ ] O-ring installed; groove clean and grease applied
[ ] Lid torqued to spec (M3: 0.5 N·m; M4: 1.0 N·m)
[ ] SMA/BNC connectors hand-tight + 1/4 turn
[ ] Self-amalgamating tape over connector bodies (min 2 layers)
[ ] Silicone applied at cable gland entry
[ ] Drain hole provided (bottom of enclosure, 3 mm dia)
[ ] Label: band, type, date, port ID, operator callsign
[ ] Mast clamp secure; lock-washer on clamp bolt
[ ] Drip cap installed if in direct rain exposure
[ ] Test: apply 100 mL water; no ingress after 5 minutes

D.2 Cable Entry and Weatherproofing

For each SMA or BNC connector passing through the enclosure wall:

1. Use chassis-mount SMA with PTFE gasket (Amphenol 901-9703-RFX or similar).
2. Apply Loctite 569 thread sealant to panel thread before nut.
3. After final positioning, apply bead of silicone (Dow 738 or equivalent) around connector body on exterior face.
4. Apply self-amalgamating tape starting below connector body, overlapping onto the coaxial cable for at least 50 mm.

APPENDIX E — GLOSSARY

Amplitude balance: Difference in insertion loss between two output ports of a divider or hybrid. Units: dB. Target: 0 dB (equal power split).

Axial ratio: Figure of merit for circular polarization quality. 0 dB = perfect circular; 3 dB = 2:1 ellipse; >6 dB ≈ nearly linear. Measured in dBic.

Branch-line coupler: See quadrature hybrid.

Cardioid: Heart-shaped antenna radiation pattern; maximum in one direction, null at 180° opposite. Typical of λ/4-spaced dipoles fed with 90° phase shift.

Current forcing: A feed method that enforces equal current magnitudes at array elements regardless of impedance changes due to mutual coupling. Achieved by using a hybrid coupler with high output-port isolation.

Endfire: Radiation from an array in the direction of the element axis (the direction along which elements are physically aligned and spaced).

Isolation: Attenuation between two output ports. High isolation (>20 dB) means loading one port does not affect the other.

Monopulse: A direction-finding technique using a sum (Σ) and difference (Δ) output from a rat-race coupler. Maximum sum signal + null difference = boresight.

Phased array: Multiple antenna elements fed with controlled phase and amplitude to produce a steerable or shaped radiation pattern.

Rat-race coupler: A 4-port ring hybrid providing sum and difference ports. Also called a ring coupler or hybrid ring.

Return loss: Ratio of incident to reflected power at a port: 20·log₁₀(1/|Γ|) dB. A well-matched port shows >20 dB return loss.

S-parameters: Scattering parameters; used to describe RF network behavior. S11 = input return loss. S21 = forward insertion gain/loss.

TLT: Transmission line transformer. Uses coax or twisted-pair on a ferrite core; provides wideband operation because signal travels in TEM mode.

Wilkinson divider: A 3-port power divider providing equal-power in-phase outputs with resistive port isolation. First described by E. Wilkinson in 1960.

End of TM-HYB-001 Rev A

Documentation standard: TM-HYB-001 follows Navy technical manual format. For corrections or additions, file at project issue tracker.