================================================================================ SCHEMATIC: Snap-On Ferrite Bead Common-Mode Chokes TM-CMC-001 Rev A Mix 31 and Mix 43 Clamshell / Snap-On Ferrite Cores Covers: 1 MHz through 300 MHz (bead dependent) ================================================================================ SNAP-ON BEAD THEORY ─────────────────── Snap-on ferrite cores (also called clamshell cores or split ferrites) clamp around existing cables without cutting connectors. A single snap-on bead on a coax cable provides 100–500 Ω of common-mode impedance. For adequate choking (>1000 Ω), multiple beads must be stacked in series. Each additional bead adds impedance in series (not parallel): Z_total = N_beads × Z_single_bead (approximation; mutual coupling minor) Stacking vs. multiple passes: Threading cable through same bead N times: Z × N² (inductive, adds as N-turn coil) N separate beads, 1 pass each: Z × N (resistive + inductive, more broadband) For broadband suppression: multiple beads preferred For single-frequency (powerline noise): multiple turns preferred ================================================================================ SNAP-ON BEAD TYPES AND IMPEDANCE DATA ================================================================================ TYPE 1: Fair-Rite 0431167251 (Mix 31, 1.125" split core, fits up to RG-8) Dimensions: 28.6mm × 28.6mm × 28.6mm aperture dia 16mm A_L ≈ 7600 nH/N² (1 turn through aperture) Single bead impedance (1 pass through aperture): f (MHz) | R (Ω) | jX (Ω) | |Z| (Ω) --------|-------|--------|-------- 0.5 | 5 | 155 | 155 1.0 | 15 | 270 | 270 5.0 | 85 | 490 | 497 10.0 | 175 | 480 | 511 25.0 | 380 | 420 | 565 50.0 | 530 | 280 | 600 100.0 | 500 | 100 | 510 200.0 | 350 | -80 | 359 300.0 | 200 | -120 | 234 TYPE 2: Fair-Rite 0431164281 (Mix 31, 2.4" split core, fits up to 1" cable) Dimensions: 61mm × 61mm × 28.6mm aperture dia 24.4mm Higher impedance per bead: f (MHz) | |Z| single bead (Ω) --------|-------------------- 1.0 | 520 5.0 | 1100 10.0 | 1300 25.0 | 1450 50.0 | 1350 100.0 | 1050 TYPE 3: Laird 28B0350-000 (Mix 31 equivalent, 1.4" snap-on, fits RG-58/RG-8X) Standard catalog item; widely available from Mouser, Digi-Key: f (MHz) | |Z| single bead (Ω) --------|-------------------- 1.0 | 290 10.0 | 480 25.0 | 540 50.0 | 510 100.0 | 430 TYPE 4: Fair-Rite 0443167251 (Mix 43, same physical as Type 1) Mix 43 has lower impedance at HF but extends better to 100–300 MHz: f (MHz) | R (Ω) | jX (Ω) | |Z| (Ω) --------|-------|--------|-------- 1.0 | 5 | 80 | 80 5.0 | 25 | 290 | 291 10.0 | 65 | 440 | 445 25.0 | 250 | 510 | 570 50.0 | 490 | 460 | 672 100.0 | 680 | 280 | 735 200.0 | 650 | 50 | 652 300.0 | 480 | -80 | 487 ================================================================================ STACKING CALCULATION — REQUIRED BEADS BY BAND AND TYPE ================================================================================ Target: |Z_total| ≥ 1000 Ω (minimum adequate) |Z_total| ≥ 3000 Ω (good suppression) Using Fair-Rite 0431167251 (Type 1, Mix 31) beads, N beads in series: Band | f (MHz) | |Z|_1bead | Beads for 1000Ω | Beads for 3000Ω ------|---------|-----------|-----------------|------------------ 160M | 1.8 | 260 | 4 | 12 80M | 3.5 | 360 | 3 | 9 40M | 7.0 | 490 | 3 (560Ω) | 7 30M | 10.1 | 505 | 2 | 6 20M | 14.0 | 545 | 2 | 6 17M | 18.1 | 575 | 2 | 6 15M | 21.0 | 590 | 2 | 6 12M | 24.9 | 605 | 2 | 5 10M | 28.0 | 600 | 2 | 5 6M | 50.0 | 600 | 2 | 5 2M | 144.0 | 480 | 3 (approx) | 7 (approx) PRACTICAL SNAP-ON BEAD STACKS: Stack name | Beads | Type | Useful range | Application -----------------|-------|--------|--------------|----------------------------- "HF-3" stack | 3 | Mix 31 | 3–50 MHz | 40M-6M quick install "HF-6" stack | 6 | Mix 31 | 1.8–50 MHz | 80M-6M good suppression "HF-12" stack | 12 | Mix 31 | 1.8–50 MHz | 160M-6M serious suppression "VHF-4" stack | 4 | Mix 43 | 10–300 MHz | 10M-2M, mix43 better VHF "Wideband-8" |4×31+4×43| mixed| 1.8–300 MHz | Mixed material wideband ================================================================================ SCHEMATIC — SNAP-ON BEAD INSTALLATION ================================================================================ COAX LINE (end view, snap-on beads clamped around outer jacket): ───────────────────────────────────────────────────────────── coax outer jacket │ │ │ │ │ │ [B1] [B2] [B3] [B4] [B5] [B6] snap-on beads │ │ │ │ │ │ ───────────────────────────────────────────────────────────── coax outer jacket Bead spacing: 2–5mm between beads (touching OK; small gap prevents stress) Total length of 6-bead stack: ~200mm on RG-8X (32mm per bead × 6) Secure stack with cable ties or self-amalgamating tape wrap MULTIPLE PASS (N-TURN EQUIVALENT) — FOR POWERLINE / MAINS CABLES: CABLE enters bead, loops back, passes through again N times: cable in ──► [BEAD aperture pass 1] ──loop──► [aperture pass 2] ──loop──► exit Impedance scales as N² (inductive behavior): 1 pass: |Z| = 270 Ω @ 1 MHz (Type 1, Mix 31) 2 passes: |Z| ≈ 4 × 270 = 1080 Ω @ 1 MHz 3 passes: |Z| ≈ 9 × 270 = 2430 Ω @ 1 MHz 4 passes: |Z| ≈ 16 × 270 = 4320 Ω @ 1 MHz CAUTION: multiple passes resonant frequency shifts DOWN. High-frequency performance degrades faster than single-pass multi-bead approach. Use multiple-pass for troublesome LF (AM broadcast, powerline) interference. Use series single-pass beads for broadband HF/VHF suppression. ================================================================================ SNAP-ON BEAD — INTERNAL CROSS-SECTION DIAGRAM ================================================================================ Top view of clamshell bead (Type 1, Mix 31): ┌──────────────────────────────────────────┐ │ ██████████████████████████████████████ │ │ ██ ┌────────────────┐ █████████████ │ │ ██ │ APERTURE │ █████████████ │ ← ferrite material (██) │ ██ │ (cable passes │ █████████████ │ │ ██ │ through) │ █████████████ │ │ ██ └────────────────┘ █████████████ │ │ ██████████████████████████████████████ │ └──────────────────────────────────────┬─┘ │ hinge / snap closure ┌──────────────────────────────────────┘ │ (mirror of top half — snaps closed) │ └──────────────────────────────────────┘ ================================================================================ SNAP-ON BEAD INSTALLATION GUIDE ================================================================================ INSTALLATION ON COAXIAL CABLE: 1. Clean cable jacket with isopropyl alcohol; remove any grit. 2. Mark bead positions (2–5mm spacing recommended). 3. Snap bead open; lay cable in lower half groove. 4. Snap closed; confirm secure closure (no gap at seam). 5. Verify cable jacket not pinched at bead edges. 6. Secure with 2-inch cable tie or tape wrap if beads will be moved. INSTALLATION ON POWER/ETHERNET/USB CABLES: Same procedure. For small cables (USB), fold cable once before inserting to increase effective turns (fold = 2 passes): USB cable folded once through Mix 31 bead: |Z| ≈ 4 × 270 = 1080 Ω @ 1 MHz POSITION ON FEEDLINE: - Feedline snap-on beads: install at entry point to shack (at bulkhead). - Equipment supply cable: install at equipment power inlet. - Monitor/display cables: install at display end (where entering equipment). - Ferrite beads do NOT need to be installed at antenna feedpoint for filtering of common-mode currents entering the shack — shack entry is correct location. - For antenna feedpoint balun action: use wound toroid (sch_toroid_choke_hf.txt) ================================================================================ WIDEBAND SNAP-ON CHOKE FOR 160M–2M (RECOMMENDED CONFIGURATION) ================================================================================ Use 4 beads of Mix 31 followed by 4 beads of Mix 43 on same coax: TX ──── [B1 M31][B2 M31][B3 M31][B4 M31] [B5 M43][B6 M43][B7 M43][B8 M43] ──── ANT Total impedance (approximate): f (MHz) | M31 ×4 (Ω) | M43 ×4 (Ω) | Combined (Ω) | CMR @ 150Ω path --------|------------|------------|-------------|------------------ 1.8 | 1040 | 320 | 1360 | 19.7 dB 7.0 | 1960 | 1780 | 3740 | 28.0 dB 14.0 | 2180 | 2680 | 4860 | 30.2 dB 28.0 | 2400 | 2940 | 5340 | 31.1 dB 50.0 | 2400 | 2688 | 5088 | 30.6 dB 144.0 | 1920 | 2940 | 4860 | 30.2 dB This 8-bead wideband configuration covers 160M through 2M adequately without any rewinding or component changes. Total package: ~300mm of cable. ================================================================================ PARTS LIST — SNAP-ON BEAD CHOKES ================================================================================ Item | Qty | Part Number | Description | Qty/kit -----|------|----------------------|-------------------------------|-------- B1 | 1+ | Fair-Rite 0431167251 | Mix 31, 1.125" split, HF | 4–12 B2 | 1+ | Fair-Rite 0443167251 | Mix 43, 1.125" split, HF/VHF | 4–8 B3 | 1+ | Laird 28B0350-000 | Mix 31 equiv, 1.4" (RG-8X) | alt for B1 Tie | var | Cable tie 4" | Secure bead stacks | 20/pack Tape | 1 | Self-amalg. tape | Optional weatherproof wrap | 1 roll Bag | 1 | Zip-lock heavy duty | Storage and transport of beads| 3/bag set ================================================================================