================================================================================ INLINE DIRECTIONAL POWER METER — TM-PWR-INLINE-001 Rev A Forward + Reflected power, auto-ranging 1W–3kW, SO-239/N-type HF / VHF / UHF coverage with band-select switch ================================================================================ COMPLETE CIRCUIT SCHEMATIC ─────────────────────────────────────────────────────────────────────────────── ┌─────────────────────────────────────────────────────────────────────────┐ │ DIRECTIONAL COUPLER │ │ │ │ RF IN ──────────────────────────────────────────────── RF OUT │ │ J1 SO-239 ←──── CENTER CONDUCTOR Z0=50Ω ────→ J2 SO-239 │ │ │ │ ┌──────────────────────────────────────┐ │ │ │ T1: TOROID COUPLER │ │ │ │ Primary: 1 turn (center line) │ │ │ │ Secondary: N turns (selectable) │ │ │ │ Core: FT-114-43 (HF) or BN-43-202 │ │ │ └──────────┬──────────────┬────────────┘ │ │ │ │ │ │ SEC(+) SEC(-) │ │ FWD coupling REF coupling │ └───────────────────────┼──────────────┼──────────────────────────────────┘ │ │ ┌───────────────────────┼──────────────┼──────────────────────────────────┐ │ FORWARD DETECTOR PATH │ REFLECTED DETECTOR PATH │ │ │ │ │ SEC(+)─►[D1 1N5711]─┬─ VFWD SEC(-)─►[D2 1N5711]─┬─ VREF │ │ │ │ │ │ R1 51Ω C1 10nF R2 51Ω C2 10nF │ │ (term.) │(RF byp) (term.) │(RF byp) │ │ │ │ │ │ │ │ GND GND GND GND │ │ │ │ VFWD ─┬─[R3 10kΩ]─┬──────────────── ADS1115 A0 │ │ │ │ │ │ C3 C4 │ │ 100nF 10µF │ │ (HF) (bulk) │ │ │ │ │ │ GND GND │ │ │ │ VREF ─┬─[R4 10kΩ]─┬──────────────── ADS1115 A1 │ │ │ │ │ │ C5 C6 │ │ 100nF 10µF │ │ │ │ │ │ GND GND │ └─────────────────────────────────────────────────────────────────────────┘ ┌──────────────────── AUTO-RANGE ATTENUATOR ────────────────────────────┐ │ │ │ VFWD ──┬─────────────────────────────────── Range 1 (1–10W) direct │ │ │ │ │ └──[20dB PAD]──┬───────────────── Range 2 (10–100W) │ │ └──[30dB PAD]──┬───────────────── Range 3 (100–1000W) │ │ └──[35dB PAD]──┴───────────────── Range 4 (1kW–3kW) │ │ │ │ Range selected by: │ │ Analog: 4-position rotary switch SW1 │ │ Digital: Auto-detect by ESP32 (2 GPIO-controlled relays) │ │ │ │ 20dB Pi-pad (50Ω): │ │ ──[R_s1 39Ω]──┬──[R_s2 39Ω]── │ │ R_p 180Ω │ │ │ │ │ GND │ │ │ │ 30dB Pi-pad (50Ω): │ │ ──[R_s1 12Ω]──┬──[R_s2 12Ω]── │ │ R_p 62Ω │ │ │ │ │ GND │ └────────────────────────────────────────────────────────────────────────┘ ┌──────────────── TEMPERATURE COMPENSATION ─────────────────────────────┐ │ │ │ VREF_3V3 ──[R_bias 10kΩ]──┬──── ADC_TEMP (ADS1115 A2) │ │ │ │ │ NTC1 │ │ 10kΩ/B3950 (NTC thermistor) │ │ mounted adjacent to D1, D2 │ │ │ │ │ GND │ │ │ │ Compensation algorithm (in firmware): │ │ T_now = f(V_ntc) [from Steinhart-Hart: 1/T = A + B×ln(R) + C×ln³(R)]│ │ K_comp = exp(alpha × (T_now – T_cal)) │ │ P_corrected = P_measured / K_comp │ │ alpha ≈ 0.023/°C for 1N5711, 0.018/°C for HSMS-2822 │ └────────────────────────────────────────────────────────────────────────┘ ┌──────────────────── OVERLOAD PROTECTION ──────────────────────────────┐ │ │ │ Strategy 1: Schottky limiter on coupler secondary │ │ │ │ SEC(+) ──►─[D1]─┬──── VFWD_DET │ │ │ │ │ ──►──[D3 BAT54]── VCLAMP = 0.3V (soft clamp) │ │ │ │ │ GND │ │ │ │ Strategy 2: Gas discharge tube + TVS on detector output │ │ │ │ VFWD_DET ──[R_prot 100Ω]──┬── To ADC │ │ │ │ │ Z1: TVS 5.1V (P6KE5.1A) │ │ │ │ │ GND │ │ │ │ Strategy 3: High-power relay bypass (> threshold) │ │ │ │ SWR > LIMIT ──► Comparator ──► GPIO ──► Relay ──► RF bypass │ │ or P_fwd > P_max (disconnects meter circuit) │ └────────────────────────────────────────────────────────────────────────┘ ┌────────────────────────── PEAK DETECTOR ──────────────────────────────┐ │ │ │ VFWD ──►─[D4 BAT54]─┬──── VPEAK │ │ (fast forward) │ │ │ C_pk 1µF R_leak 1MΩ │ │ │ / │ │ ├───────┤ (30s decay if 1MΩ×1µF = τ=1s) │ │ │ \ │ │ GND │ │ │ │ VPEAK ──── ADS1115 A3 (separate from average VFWD on A0) │ │ │ │ Peak hold time: τ = R_leak × C_pk │ │ Fast hold (1s): R=1MΩ, C=1µF │ │ Slow hold (5s): R=4.7MΩ, C=1µF │ │ Manual reset: GPIO pulls C_pk to GND via 2N7000 MOSFET │ └────────────────────────────────────────────────────────────────────────┘ ┌───────────── BAND SWITCH RELAY (auto-coupler select) ─────────────────┐ │ │ │ SW_BAND (3-pos): HF = T1 FT-114-43 32T secondary │ │ VHF = T1 BN-43-202 20T secondary │ │ UHF = on-PCB coupled microstrip │ │ │ │ Each secondary output routes through relay to detector. │ │ Only one secondary is active at a time. │ │ HF/VHF coupler secondaries are wound on same core using │ │ separate winding taps, OR separate PCB modules. │ └────────────────────────────────────────────────────────────────────────┘ COMPONENT VALUES BY POWER/RANGE ─────────────────────────────────────────────────────────────────────────────── Power Range Coupler Sec N2 Coupling (dB) Pi-pad In Path R1,R2 term ───────────── ─────────────── ───────────── ────────────── ────────── 1–10W 32T –30 dB none 51Ω 10–100W 32T –30 dB 20 dB pad 51Ω 100–1000W 32T –30 dB 30 dB pad 51Ω 1kW–3kW 32T –30 dB 35 dB pad 51Ω Alternatively, change secondary turns for each range: 10W range: N2=10T, C= –20 dB 100W range: N2=32T, C= –30 dB 1kW range: N2=100T, C= –40 dB 3kW range: N2=178T, C= –45 dB Note: More secondary turns = lower coupling = better for high power Note: More secondary turns = higher inductance = better HF response Trade-off: parasitic capacitance limits upper frequency as N2 increases PERFORMANCE SPECIFICATIONS ─────────────────────────────────────────────────────────────────────────────── Frequency range : 1.8 – 30 MHz (HF), 50–148 (VHF), 420–1300 (UHF) Power range : 1W – 3kW (4 ranges, switchable or auto) Insertion loss : < 0.1 dB (all bands and ranges) Directivity : > 28 dB (HF), > 22 dB (VHF), > 18 dB (UHF) SWR accuracy : ±5% FSD after calibration Power accuracy : ±10% FSD (±5% with calibration) Peak detector : < 1 µs rise time (BAT54 Schottky, Cj=10 pF) Average display : 200ms rolling average (firmware) Overload : TVS clamp at 5.1V on detector output ================================================================================ END OF INLINE DIRECTIONAL METER — TM-PWR-INLINE-001 Rev A ================================================================================