The 3.5T Air Core Copper Inductor Coil is a precision-wound, wire-hollow (coreless) RF inductor engineered for high-frequency resonant circuits, RF tuning, signal filtering, and wireless communications. Constructed using 0.7mm high-purity enameled copper wire with an inner diameter of 3.5mm, this 3.5-turn air-core inductor delivers an ultra-high Quality factor (Q-factor), zero magnetic core saturation, extremely low parasitic capacitance, and stable inductance across wide temperature and frequency ranges. Supplied in a bulk 1000-piece pack, it is ideal for high-volume RF manufacturing, automated electronics assembly, FM/VHF radio production, and DIY RF prototyping.

Specifications

• Product Type: Wire-Hollow Air Core Inductor / RF Choke Coil
• Number of Turns: 3.5 Turns (3.5T)
• Wire Gauge / Diameter (G): 0.7mm Enamelled Copper Wire
• Inner Coil Diameter (D): 3.5mm (±0.2mm)
• Inductance Range: Approx. 20nH to 35nH (Depending on turn spacing and lead length)
• Core Type: Air Core (Hollow / Non-Magnetic)
• Conductor Material: 99.9% High-Purity Polyurethane/Polyester Enameled Copper Wire
• Lead Finish: Pre-stripped and pre-tinned for direct, easy soldering
• Operating Frequency Range: VHF / UHF (Typically 50 MHz to 500+ MHz)
• DC Resistance (DCR): Extremely Low (< 0>
• Current Handling Capability: High (≥ 3.0A to 5.0A continuous depending on ambient cooling)
• Operating Temperature Range: -40°C to +125°C
• Pack Quantity: 1000 Pieces (Full Bulk Pack)

Features

• Zero Core Saturation & No Core Loss: Air core design completely eliminates magnetic saturation and core hysteresis losses, ensuring perfectly linear inductance under high RF power levels.
• High Quality Factor (Q): Heavy 0.7mm enameled copper wire significantly minimizes skin-effect resistance at VHF/UHF frequencies for sharp resonance and minimal signal attenuation.
• Pre-Tinned Solder Leads: Leads are stripped of enamel and pre-tinned with solder for fast through-hole PCB insertion and clean wave or manual soldering.
• Mechanically Rigid Construction: 0.7mm wire provides excellent structural stiffness, preventing accidental deformation and inductance drift during handling and operation.
• Ultra-Low Parasitic Capacitance: Open-turn spacing ensures very high self-resonant frequency (SRF) well into the gigahertz region.

Common Applications

• FM & VHF Transmitters / Receivers: LC tank tuning, local oscillators, and intermediate frequency (IF) filters.
• RF Power Amplifiers: Inter-stage matching networks and DC supply RF chokes for VHF/UHF amateur radio and commercial transceivers.
• Wireless Communication Modules: High-frequency filtering and antenna matching in 315MHz / 433MHz / 868MHz wireless telemetry modules.
• Low-Pass & Band-Pass Filters: Harmonic suppression and band-selection filters for RF front-ends.
• RFID & Remote Control Systems: Resonant inductive coupling in transmitters and wireless access keycards.

Usage Tips

• Manual Fine-Tuning: Air core inductors can be easily tuned by gently compressing the turns together to increase inductance, or stretching them apart to decrease inductance.
• Soldering Precaution: Solder directly to the pre-tinned lead sections without overheating to prevent insulation enamel burn-back on the active turns.
• Placement & Proximity: Keep the inductor slightly elevated and away from large metal shielding cans or ground planes to avoid eddy current losses that can lower the coil's Q-factor.
• Component Securing: In high-vibration applications, secure the coil to the PCB using a drop of non-conductive electronic-grade RTV silicone or hot-melt adhesive.