Need help, Inductor design

Janis59

Joined Aug 21, 2017
1,576
RE:""It specifies ferrite cores without any indication of what type.""
Mostly RF coils uses ferrite screw-rod NOT as the coil core. But for just nearing it to or from coil outer perimeter adjust the exact frequency. For example, core may stand 1 cm outside the turns. In such case the question how thick, long or what mju must have the ferrite is sense-less. ANY is useful IF THE MAX FREQUENCY of ferrite material is acceptable. Just chech at shop page what is max permissible frequency and quess that ferrite may have sth 5-50 mju value.
 

BobTPH

Joined Jun 5, 2013
6,304
RE:""It specifies ferrite cores without any indication of what type.""
Mostly RF coils uses ferrite screw-rod NOT as the coil core. But for just nearing it to or from coil outer perimeter adjust the exact frequency. For example, core may stand 1 cm outside the turns. In such case the question how thick, long or what mju must have the ferrite is sense-less. ANY is useful IF THE MAX FREQUENCY of ferrite material is acceptable. Just chech at shop page what is max permissible frequency and quess that ferrite may have sth 5-50 mju value.
You may be right, but an RF choke is not normally tunable. The inductance would have been more useful.
 

Janis59

Joined Aug 21, 2017
1,576
I cant see there any choke but the resonant tank system. At 1 Watt I am sure the air-core is effective enough. If indeed some certain coil is meant the ring-cored, then only circular cross-section have real importance. May easy back-engineering from known capacitances what must be the inductance, thus making on existing ring turns and seeing the inductance value is wrong, may re-calc the turn count.
 

BobTPH

Joined Jun 5, 2013
6,304
I cant see there any choke but the resonant tank system. At 1 Watt I am sure the air-core is effective enough. If indeed some certain coil is meant the ring-cored, then only circular cross-section have real importance. May easy back-engineering from known capacitances what must be the inductance, thus making on existing ring turns and seeing the inductance value is wrong, may re-calc the turn count.
From the article linked:

L1 = rf choke (20 turns, 0.2mm on ferrite core, 0.3mm)

I am guessing one of the dimensions is wire diameter, but what could the second one be? Certainly not the the diameter of the core.
 

Janis59

Joined Aug 21, 2017
1,576
Sure the 0.2 may pass to wire nomenclature. Because 0.3 sure NOT pass to cores nomenclature, probably it refers to DISTANCE between turns. In 100++ MHz it is rather wide used method to use the turns with the gap.
 
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