================================================================================ SCHEMATIC: LUMPED-ELEMENT HYBRIDS FOR COMPACT HF DESIGNS TM-HYB-001 Rev A L-C networks; single-band and switchable multiband 160M – 10M; compact, hand-portable, weatherproof ================================================================================ OVERVIEW -------- At HF frequencies, quarter-wave transmission line sections are impractically long. Lumped L-C networks can substitute for λ/4 sections in all hybrid designs, trading bandwidth for compactness. Single-section lumped approximation (bandwidth ≈ 40% of center frequency): L = Z / (2πf₀) [series inductor] C = 1 / (2πf₀ × Z) [shunt capacitor] Multi-section approximation (Chebyshev or Butterworth, wider bandwidth): 2 sections: bandwidth ≈ 80% 3 sections: bandwidth ≈ 150% This file covers four compact HF hybrid designs: 1. Band-switched Wilkinson divider (160M–10M) 2. Band-switched quadrature hybrid (160M–10M) 3. Wideband HF hybrid using ferrite transmission lines 4. VSWR/isolation bridge for production test ================================================================================ DESIGN 1: BAND-SWITCHED WILKINSON DIVIDER (160M–10M) ================================================================================ OVERVIEW: Single PCB with switched L and C values for each band. Rotary switch or relay array selects component sets. CYD firmware monitors SWR and amplitude balance at each port. SCHEMATIC (one arm shown; duplicate for arm B): PORT 1 ──┬─── [SW_L: selects L_a/2] ─── [SW_C: selects C] ─── [SW_L: selects L_a/2] ───┬─── PORT 2 │ │ │ [R_iso = 100Ω] │ │ └─── [SW_L: selects L_b/2] ─── [SW_C: selects C] ─── [SW_L: selects L_b/2] ───┘─── PORT 3 SW_L: 12-position rotary switch; 10 positions for 160M–10M, 2 spare. SW_C: 12-position rotary switch (or relay matrix for remote switching). COMPONENT MATRIX (both arms identical, values per arm): Pos Band f₀(MHz) L_total(µH) L/2(µH) C_shunt(pF) --- ---- ------- ----------- ------- ----------- 1 160M 1.850 6.08 3.04 1216 2 80M 3.750 3.00 1.50 601 3 40M 7.150 1.574 0.787 315 4 30M 10.125 1.111 0.556 222 5 20M 14.175 0.793 0.397 159 6 17M 18.118 0.621 0.311 124 7 15M 21.225 0.530 0.265 106 8 12M 24.940 0.451 0.226 90 9 10M 28.850 0.390 0.195 78 10 6M 50.500 0.223 0.111 44.7 11–12 (spare) INDUCTOR CONSTRUCTION TABLE: All on T-50-6 (yellow) or T-37-6 cores; #26 AWG: Band Core Turns Expected L (µH) Wire length (cm) ---- ---- ----- --------------- ---------------- 160M T-94-2 22 6.1 62 80M T-68-2 16 3.0 44 40M T-68-6 11 1.57 30 30M T-50-6 10 1.11 27 20M T-50-6 8 0.79 22 17M T-50-6 7 0.62 19 15M T-50-6 7 0.53 18 (adjust spacing) 12M T-37-6 8 0.45 20 10M T-37-6 7 0.39 18 6M T-37-6 5 0.22 14 Wind evenly distributed; measure with LC meter before installation. Target: ±3% of tabulated value. CAPACITOR SELECTION: All NP0/C0G type; ±5% tolerance minimum. For values not available: parallel/series combination. Common E12 capacitor combinations: 1216 pF: 1200 pF + 18 pF (C0G 1200+18) 601 pF: 560 pF + 39 pF 315 pF: 270 pF + 47 pF 222 pF: 220 pF + 2.2 pF (or single 220 pF, ≈1% error) 159 pF: 150 pF + 10 pF 124 pF: 120 pF + 3.9 pF 106 pF: 100 pF + 6.8 pF 90 pF: 82 pF + 8.2 pF 78 pF: 75 pF + 3.3 pF (or 82 pF, ≈5% error) 44.7 pF: 39 pF + 5.6 pF ================================================================================ DESIGN 2: SINGLE-FREQUENCY QUADRATURE HYBRID (COMPACT HF) ================================================================================ OVERVIEW: Fixed-frequency 90° hybrid for a single band. Designed for antenna phasing in compact portable station. All four arms in compact layout, hand wound on T-50 cores. DESIGN PROCEDURE for 40M (7.150 MHz): Z_shunt_arms = 50Ω → L_sh = 50/(2π×7.15e6) = 1.113 µH Z_series_arms = 35.35Ω → L_sr = 35.35/(2π×7.15e6) = 787 nH C_sh = 1/(2π×7.15e6×50) = 446 pF C_sr = 1/(2π×7.15e6×35.35) = 630 pF SCHEMATIC (T-network per arm): [L_sh/2 = 557nH] [C_sh = 446pF] [L_sh/2 = 557nH] P1 ─────────────────────┬──────────────────────────────────────────── P2 GND [L_sh/2 = 557nH] [C_sh = 446pF] [L_sh/2 = 557nH] P4 ─────────────────────┬──────────────────────────────────────────── P3 GND P1 [L_sr/2=394nH][C_sr=630pF][L_sr/2=394nH] P4 │ ─────────────────────┬──────────────────────────────────── │ GND P2 [L_sr/2=394nH][C_sr=630pF][L_sr/2=394nH] P3 │ ─────────────────────┬──────────────────────────────────── │ GND (P1–P2 = left shunt arm; P4–P3 = right shunt arm; P1–P4 = top series arm; P2–P3 = bottom series arm) PORT SUMMARY: P1 = Input P2 = Through output (0°) P3 = Coupled output (−90°) P4 = Isolated (terminate 50Ω) 40M COMPONENT LIST: L_sh: 2 pcs × 557 nH each (wound T-50-6, ~8t, #26 AWG) L_sr: 2 pcs × 394 nH each (wound T-37-6, ~7t, #26 AWG) C_sh: 4 pcs × 446 pF (4 shunt caps: use 390 pF + 56 pF) C_sr: 4 pcs × 630 pF (4 series caps: use 560 pF + 68 pF) R_term: 1 × 50Ω (P4 termination) Total: 8 inductors, 8 capacitors, 1 termination resistor. BAND-SPECIFIC COMPACT HYBRID TABLES: Band L_sh_half(nH) C_sh(pF) L_sr_half(nH) C_sr(pF) ---- ------------- -------- ------------- -------- 80M 1059 849 749 1201 40M 557 446 394 631 30M 392 315 277 446 20M 281 225 198 318 15M 188 150 133 213 10M 138 110 97.5 156 ================================================================================ DESIGN 3: WIDEBAND HF HYBRID (1.5–30 MHz) — FERRITE TLT ================================================================================ OVERVIEW: Uses transmission line transformers (see sch_tl_transformer.txt) to build a hybrid with inherently wide bandwidth. Not limited to single frequency. WIDEBAND 3 dB HYBRID SCHEMATIC: PORT 1 ──────────────────────────────── PORT 2 (0°) │ │ [T1: 1:1 TLT balun, BN-43-3312, 6t] [R1: 100Ω, 2W] │ │ └────── reversed polarity ────────── PORT 3 (180°) This is a wideband 180° hybrid (splitter), not 90°. For WIDEBAND 90° HYBRID: Pair with an all-pass network for the 90° shift: PORT 1 ──────────────── PORT 2 (0°) │ [All-pass 90° network: L = 50/ω₀, C = 1/(50ω₀)] │ PORT 3 (−90°) Combining TLT (wideband amplitude balance) with an all-pass network (frequency-dependent phase) gives a hybrid with: Amplitude balance: < 0.3 dB, 2–30 MHz Phase balance: ±10°, 2:1 bandwidth around center Insertion loss: < 0.5 dB WIDEBAND ALL-PASS QUADRATURE NETWORK (center 14 MHz): L1 = 50/(2π×14.175e6) = 561 nH (T-50-6, 9t, #22 AWG) C1 = 1/(2π×14.175e6×50) = 225 pF (C0G) Phase: −90° at 14.175 MHz, ±10° from 8–25 MHz Bandwidth for ±5°: 10–20 MHz (2:1) ================================================================================ DESIGN 4: HYBRID PORT TEST / VSWR BRIDGE ================================================================================ PURPOSE: Inline SWR bridge measures return loss at each hybrid port. Used to verify port match before connecting to antenna or amplifier. SCHEMATIC (Wheatstone bridge SWR meter): RF IN ─────────────────────────────────────────── To DUT (hybrid port) │ [R1: 50Ω]─────────[D1: BAT43]──── FWD detector (ESP32 ADC) │ [R2: 50Ω]─────────[D2: BAT43]──── REF detector (ESP32 ADC) │ GND Bridge balance: when DUT Z = 50Ω, detectors read equal. Imbalance gives SWR reading. For CYD integration: see firmware/hybrid_monitor_cyd.ino. COMPACT PCB LAYOUT GUIDELINES ------------------------------- General HF hybrid PCB: • Star ground; single ground plane if 2-layer, or use bus wire. • Keep all inductors physically separated (>1 inductor-diameter spacing). • Orient inductor axes perpendicular to each other to minimize coupling. • Shield adjacent L-C pairs if crosstalk is suspected. • SMA or BNC connectors at PCB edges. Board sizes (typical): Single-band HF (80M-20M): 60 × 60 mm Band-switched (160M-10M): 100 × 80 mm VHF/UHF hybrid: 50 × 50 mm PERFORMANCE EXPECTATIONS -------------------------- Parameter Single-section 2-section TLT wideband --------- ------------- --------- ------------ Bandwidth 40% of f₀ 80% of f₀ 1.5–50 MHz Insertion loss < 0.3 dB < 0.4 dB < 0.5 dB Return loss > 18 dB > 18 dB > 20 dB Isolation > 18 dB > 18 dB > 15 dB Phase balance < 2° < 3° < 5° Amplitude bal. < 0.2 dB < 0.3 dB < 0.3 dB PARTS LIST — DESIGN 1 (BAND-SWITCHED WILKINSON) ------------------------------------------------- Ref Qty Value/Part Description --- --- ---------- ----------- SW1 1 12-pos rotary L selection (Electroswitch series) SW2 1 12-pos rotary C selection L1–L20 20 per table Wound toroids (2 per band per arm) C1–C20 20 per table NP0/C0G capacitors R_iso1,2 2 100Ω, 1W Isolation resistors J1–J3 3 BNC or SMA Ports 1, 2, 3 PCB 1 100 × 80 mm Single-sided phenolic or FR-4 Knob 2 6.4mm shaft Rotary switch knobs PARTS LIST — DESIGN 2 (SINGLE-BAND QUADRATURE) ------------------------------------------------ Ref Qty Value/Part Description --- --- ---------- ----------- L1–L8 8 per band table Wound T-50 toroids C1–C8 8 per band table NP0/C0G capacitors R_term 1 50Ω, 1W Isolated port termination J1–J4 4 SMA or BNC Four ports PCB 1 60 × 60 mm FR-4 ================================================================================