EF Johnson
EF Johnson 153-508-4 Dual Section Air Variable Capacitor 18-57 pF Each Section
- MPN:
- 153-508-4
- Condition:
- Used
- Shipping:
- $12.00 (Fixed Shipping Cost)
Frequently bought together:
Description
EF Johnson 153-508-4 Dual Section Air Variable Capacitor 18-57 pF Each Section
Specifications & Information Genuine E.F. Johnson Co. (Waseca, MN) dual-section air-variable capacitor, model 153-508-4 (closely related to the catalog Type “D” / 50DD70 series of medium-power RF capacitors).
measured / stated specs:
Typical values for the close 153-508 were ~15–52 pF max/min, 0.175″ plate spacing, 8 plates per section in the base listing (your unit appears to have a similar or slightly variant plate count consistent with the measured higher max capacitance). Construction features heavy aluminum end frames, .051″ aluminum plates, 5/16″ tie rods, low-loss steatite insulators, and laminated phosphor-bronze rotor contacts (center contact on duals for symmetry). Shaft is typically ¼″ cadmium-plated with rear extension on many models.
These high-Q, rugged air variables were designed for medium-power RF use in amateur-radio transmitters, linear amplifiers, antenna tuners, and similar equipment. Dual-section design allows simultaneous tuning of two circuits or series/parallel connection for higher total capacitance.
- Sections: 2 (independent stator sections on a common rotor shaft)
- Capacitance: 18–57 pF per section
- Total Capacitance 114 pF
- Dimensions: Length 7⅜″, Width 4⅜″, Height 4¼″
Typical values for the close 153-508 were ~15–52 pF max/min, 0.175″ plate spacing, 8 plates per section in the base listing (your unit appears to have a similar or slightly variant plate count consistent with the measured higher max capacitance). Construction features heavy aluminum end frames, .051″ aluminum plates, 5/16″ tie rods, low-loss steatite insulators, and laminated phosphor-bronze rotor contacts (center contact on duals for symmetry). Shaft is typically ¼″ cadmium-plated with rear extension on many models.
Voltage rating for the 0.175″ spacing family is typically in the multi-kV peak range (exact peak depends on condition and exact gap; similar units are often rated several kV).
Clean used / equipment pull. Inspect for plate alignment, free shaft rotation, and contact integrity. Classic Johnson aluminum frame with ceramic/steatite side supports visible in photos.
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