Plain-language answer: A fixed capacitor provides a nominal capacitance that is not intended for routine adjustment.
Why the real component differs from the ideal
At RF, dielectric loss, ESR, current, voltage, tolerance, temperature drift, and parasitic inductance control where it can be used.
What to verify
Select an RF-rated part for the exact frequency and stress, and measure critical parts in their installed fixture.
The common mistake
Paralleling random capacitors without checking current sharing and self-resonance.
Component boundary
Use frequency-specific ratings and the exact topology, material, geometry, load, power, duty cycle, and cooling. Begin at low power and stop for heating, odor, arcing, distortion, or unstable measurements.
