07-20-2013, 09:02 AM
Different types of caps have different strengths and weaknesses:
Disc ceramics are very good for RF bypasses, but unless they are NPO (COG) temperature stable types, their capacitance value may vary greatly with temperature and applied voltage.
Silver micas are typically used in RF tuned circuits as their capacitance value is stable with temperature and over time. Disadvantage is that they are somewhat expensive.
Film types are available in larger values and typically used as low frequency bypasses and coupling caps. Not the best choice for very high frequency RF as they have higher parasitic inductance than ceramics or micas.
Your radio operates at FM broadcast frequencies (88-108 MHz) so the RF caps can be more critical. If it were my radio, I would leave the low value caps alone for now, as the original caps are certainly either ceramic or mica. They are quite reliable and replacing them in the FM front end may cause problems with oscillations and instability.
Disc ceramics are very good for RF bypasses, but unless they are NPO (COG) temperature stable types, their capacitance value may vary greatly with temperature and applied voltage.
Silver micas are typically used in RF tuned circuits as their capacitance value is stable with temperature and over time. Disadvantage is that they are somewhat expensive.
Film types are available in larger values and typically used as low frequency bypasses and coupling caps. Not the best choice for very high frequency RF as they have higher parasitic inductance than ceramics or micas.
Your radio operates at FM broadcast frequencies (88-108 MHz) so the RF caps can be more critical. If it were my radio, I would leave the low value caps alone for now, as the original caps are certainly either ceramic or mica. They are quite reliable and replacing them in the FM front end may cause problems with oscillations and instability.
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