ferrite toroids vs iron powder - frequency stability issues
时间：04-07
整理：3721RD
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hello there,
I am to chose between ferrite toroids and iron powder for my QRP rig. the cores will be used in frequency sensitive area of the circuit, just right after a crystal to alter it's frequency.
These FT cores have better winding to inductance ratio but they have 12000 ppm stability whereas some iron powder ones have as low as 35 ppm.
Which ones should I chose for better frequency stability?
Is it a good practice to wind 100 turns on an iron powder core, whereas only 12 turns would do the job using a ferrite one? (in terms of losses due to more wire length, etc)
I am to chose between ferrite toroids and iron powder for my QRP rig. the cores will be used in frequency sensitive area of the circuit, just right after a crystal to alter it's frequency.
These FT cores have better winding to inductance ratio but they have 12000 ppm stability whereas some iron powder ones have as low as 35 ppm.
Which ones should I chose for better frequency stability?
Is it a good practice to wind 100 turns on an iron powder core, whereas only 12 turns would do the job using a ferrite one? (in terms of losses due to more wire length, etc)
As a first point, you should refer to the ferrite core expectable Q specification as well. It may affect the overall quality more than the wire.
Secondly, an ungapped ferrite core rarely achieves good TC numbers. Iron powder cores, particularly lower μr RF types have a build-in distributed "gap" and are much more stable thus. To achieve similar (or possibly better) quality with ferrite cores, you have to choose other forms than toroid.