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Ceramic RF high voltage doorknob capacitors

The doorknob capacitors

Ceramic RF High Voltage capacitors are commonly referred to as doorknob capacitors. These capacitors have many applications in industries such as:

  • transmitters
  • shortwave transmissions
  • induction heating
  • electrical welding equipment
  • antenna coupling and decoupling
  • x-ray machines
  • RF (radio frequency)
  • heating devices

Typical high voltage RF capacitors voltages range from 5KVDC to 20KVDC, the most popular being between 7.5KVDC and 15KVDC. Popular temperature coefficients are NPO (means negative positive 0), N750 (manufactured in clean rooms facilities).

Tolerance of this type of capacitors usually is 10%. The typical mounting styles for these doorknob capacitors are axial lead and threaded terminal 6/32 for 7.5KV and 10/32 for 15KV.

The material used in the manufacturing of high voltage ceramic capacitors is titanate which offers an excellent temperature compensating property (when other components change in the circuit, this allows a constant resonant frequency). These capacitors can withstand high RF voltages without breaking down. Being oval in shape, these RF capacitors minimize inductance while excelling in voltage optimization.

Doorknob capacitors popular values

Popular values of doorknob capacitors are:

  • 3pf, 5pf, 10pf, 20pf, 40pf at 5000 volts
  • 25pf, 50pf, 75pf, 100pf, 500pf, 0.001 uf at 7500 volts
  • At 15KV standard capacitances are typically 25pf, 50pf, 100pf and when going to 200pf, voltage is regulated to 7500 Volts
  • Other capacitances are available upon special request

Standard sizes:

  • HT 53, 853 0.43 x 0.5 inch (11 x 12.7 mm)
  • HT 854, 855 0.375 x 0.355 inch (9.5 x 9.5 mm)
  • HT 58, 8503 0.75 x 0.89 inch (19 x 22.6 mm)
  • HT 57, 857 1.187 x 1.89 inch(30 x 47.9 mm)

TEDSS.com is happy to produce this convenient cross reference chart from older numbers by Centralab and Philips, to the current production numbers.

Cast epoxy high voltage capacitors

Another capacitor often referred to as a doorknob capacitor is the cast epoxy high voltage capacitor manufactured by Ceramite. These capacitors range from 10,000 volts thru 40,000 volts. Tolerances are either -20%+80% or 20%. These high voltage ceramic transmitting capacitors are typically used in radio transmitters, lasers, and high-power power supplies.

The temperature rating of the doorknob is 85°C standard. They are mounted by terminal adapters typically with 8/32 tapping.

These extremely reliable and rugged capacitors can be found at Tedss.com. They have the best prices around. At Tedss.com you have access to a huge on-the-shelf availability of inventory.

Click here to browse our ceramic transmitting doorknob capacitors.

Examples of rf high voltage (doorknob) capacitors

851-25 853-20Z HH58T501ML 857-40N 30KTD12 2073-CM76
Picture of 851 series doorknob capacitor. Picture of 853 series doorknob capacitor. Picture of HH58 series doorknob capacitor. Picture of 857 series doorknob capacitor. Picture of 30KTD series doorknob capacitor. Picture of CM76 series doorknob capacitor.
25pF 15000V 20pF 5000V 500pF 7500V 40pF 15000V 1200pF 30000V 430pF 6000V

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