20-1000PF 1000V Air Dielectric Variable Capacitor: Complete Technical Guide
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What is the 20-1000PF air variable capacitor?
This is a single-section air-dielectric variable capacitor spanning roughly 20 to 1000 pF at a 1000 V working rating: aluminium rotor and stator plate stacks on a brass 6.35 mm shaft, white insulating end supports, a galvanised steel frame with top guide rods, and screw-terminal studs on insulated posts at the base. It ships with a 3590B-style precision dial knob bored for the 6.35 mm shaft. One unit, new, built by Shenzhen Jianxingda Electronics (inspection record dated 16 December 2024), 1.5 kg. All 9 photos and 1 video below show the exact unit covered by this record.
Part details
| Field | Value |
|---|---|
| Type | Single-section air-dielectric variable capacitor |
| Capacitance range | approx. 20 - 1000 pF |
| Voltage rating | 1000 V (as recorded at intake) |
| Construction | Aluminium rotor and stator stacks, white insulating end supports, galvanised steel frame with top guide rods |
| Shaft | Brass, 6.35 mm with flats |
| Terminals | Screw studs on insulated posts at the base |
| Included knob | 3590B-style precision dial knob, 6.35 mm bore |
| Maker | Shenzhen Jianxingda Electronics Co. (inspection no. Q/JXD 001-2024) |
| Factory date | 2024-12-16, order 1005010, serial 14 |
| Quantity | 1, new |
| Shipping weight | 1.5 kg |
Mechanical details are read from the photo set; the capacitance span and voltage rating follow the intake record and the product listing.
What a 1000 V air variable is built for
At a 1000 V rating this is not a receiver-grade tuning cap — it is built for circuits where RF voltage swings large: antenna tuners matching wire antennas on HF, the tank circuit of a small tube or transistor transmitter, a magnetic-loop loop capacitor, or a high-voltage lab oscillator. Air dielectric is the reason it can do that: with nothing but air between the aluminium plates there is almost no loss to warm up and no voltage to punch through, so the capacitor survives swings that would crack a ceramic or film part of the same value. The rotor turns on the brass shaft against ball-bearing-style end supports; the white posts are insulators, so the stud terminals on them stand off the frame. The 20 pF minimum is the residual capacitance with the rotor fully unmeshed, and the sweep to 1000 pF covers a wide matching range in one control — the included 3590B-style knob carries a graduated skirt so that sweep can be logged and repeated. KOEED also stocks the broadcast-style 365 pF dual-gang air variable for lower-voltage tuning work.
Photos and video
All images below are original KOEED warehouse photos. Click any photo to view it full size.
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