Q фактор при феритни антени
Често се сблъсквам с проблема с паразитния капацитет при намотки с голям брой навивки. Първоначално се заблудих, че използването на лицендрат не би могло да помогне (а и вероятно няма как да помогне за приложения извън комуникациите?) за редуцирането на паразитния капацитет на намотките, но съдейки от масовата практика за изработка на феритни антени с такъв проводник проверик какво се случва.

В следния сайт: http://www.bentongue.com/xtalset/29MxQFL/29MxQFL.html има подробно описание и симулации на намотки с плътен единичен проводник и лицендрат.

Цитат:Table 7 shows the benefits of spaced winding when using solid wire. All the inductors in Table 7 use centered solenoids of 58 turns and a length of 1.624".  The only variable is the diameter of the conductor, which controls the spacing of the turns (the winding pitch is held constant).  The lesson here is that, when using solid copper wire, there can be a great Q benefit by space winding the solenoid and using an optimum size wire; in this case a Q of 431.9 vs 130.1 at 1 MHz, with solid wire. One can see that core losses change very little with the various conductor diameters (Hysteresis losses in ohms). Notice how, with a conductor diameter change from 0.02530 to 0.00006300", the AC copper loss decreases from 11.6 to 3.02 ohms overwhelming the increase in DC conductor resistance from 0.16 to 2.62 ohms

В обобщение загубите от ефект на близост (proximity effect) и загубите от скин ефект трябва да се отчетат спрямо постояннотоковото съпротивление на намотката и да се преценят спрямо работната честота!

Цитат:See Table 3 for measured inductance and Q values of an inductor similar to inductor BB, but wound with 125/46 litz wire.  Here the Q is even greater than in Table 7 because litz construction is less sensitive to proximity and skin effect losses than is solid wire.

Цитат:Bulk factors that affect inductor Q:
  • Initial permeability of the ferrite material (µi) and ferrite loss-factor (LF)
  • dielectric constant (ε) and dielectric loss tangent (tan δ) of the ferrite core
  • dielectric constant (ε), dielectric loss tangent (tan δ) and length of the 'former' upon which the solenoid is wound (if one is used)
  • resistivity of the ferrite rod
  • length (lf) and diameter (df) of the rod, and their ratio
  • length (ls) and diameter (ds) of the solenoid, and their ratio
  • Ratio of the length of the solenoid to the length of the ferrite rod
  • size and type of wire (solid or litz) and spacing of the turns

Цитат:The proximity effect, but not the skin effect loss may be much reduced if the wires are space-wound.  New trade-offs now must be considered: Same wire diameter, and therefore a longer solenoid, or a smaller wire diameter and the same overall length?

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