05-27-2013, 10:24 AM
Pete
For these purposes any type of cap can be used. At these frequencies the caps behave very close to ideal cap and the currents are small.
Say, in today's digital devices or in a switching power block there's no way you could take an electrolytic cap, solder it to wires 6" long and be siccessful. In the old radios this is OK to do.
So as long as your cap meets the voltage/capacitance requirements it is OK to use.
In case of electrolytics you have to watch your polarity.
One notable exception is RF filter caps; they need to have a very good thermal drift coefficient and need to be soldered using short leads. This is why mica caps were used there; today you can use either those or NPO/C0G dielectric type ceramics.
For all your other major needs (sorry for the pun) except where the electrolhytics use is warranted due to high capacitance (there is no other reason to use them) polyester film caps will do just fine.
For these purposes any type of cap can be used. At these frequencies the caps behave very close to ideal cap and the currents are small.
Say, in today's digital devices or in a switching power block there's no way you could take an electrolytic cap, solder it to wires 6" long and be siccessful. In the old radios this is OK to do.
So as long as your cap meets the voltage/capacitance requirements it is OK to use.
In case of electrolytics you have to watch your polarity.
One notable exception is RF filter caps; they need to have a very good thermal drift coefficient and need to be soldered using short leads. This is why mica caps were used there; today you can use either those or NPO/C0G dielectric type ceramics.
For all your other major needs (sorry for the pun) except where the electrolhytics use is warranted due to high capacitance (there is no other reason to use them) polyester film caps will do just fine.
