OCR Text |
Show Radio Club Notes Conducted by G. S. Morris (SUMMARY) (Continued from last week) As has been mentioned before, an efficient transfer of energy will exist only when the circuit constants are equal; therefore in dealing with two circuits at adio frequencies, such as telephone circuits, cir-cuits, amplifiers, etc., the "impedance" "impe-dance" of each must be equal, selecting the proper impedance of two or more circuits is termed "matching the impedance." The counter EMF of a circuit comprising compris-ing a large ratio of inductance to capacity is termed "inductive loaded" load-ed" and equals the frequency multiplied by the inductance; the result then multiplied by a constant con-stant of 6.28, the result of which gives the inductive reactance at that certain frequency. From the formula then it can be seen that the higher the frequency the greater great-er will be the inductive reactance which again proves why it is necessary to reduce the value of inductance for different frequencies, frequen-cies, higher than the one designed for. Inductance designed for low frequencies incorporate an iron core by reason of the fact that the current involved is usually much higher at adio frequencies and also provides a better molecular path and consequent reduction in heat. Such a unit is known as an "iron core choke coil." Coils used in radio are known as "RF choke coils" and each performs the same act, only at different frequencies. A choke coil, as previously mentioned, men-tioned, opposes a change in current cur-rent direction and, as it tends also to prolong the original current direction di-rection it has the effect of preventing pre-venting an alternation from reaching reach-ing maximum or zero potential, which therefore means that the alternation is in effect "straightened" "straight-ened" or smoothed. This action is the prime reason why iron core coils are used in rectifying systems sys-tems such as "B" eliminators etc. |