hat
Paske antèn ki yo se pi pi kout pase 1 / 4 longèdonn prezante yon enpedans anpil ti ak trè reyaktif ki se depann sou frekans nan te resevwa, yo te pa gen okenn tantativ te fè matche ak enpedans-li antèn la nan ta pwouve twò difisil ak fwistre matche ak enpedans plis pase yon dekad nan pwoteksyon frekans. Olye de sa, sèn nan D '(Q1) se yon JFET sous-disip, ki gen gwo enpedans opinyon avèk siksè pon Karakteristik antèn la nan nan nenpòt ki frekans. Malgre ke anpil diferan kalite JFET yo kapab itilize-tankou MPF102 a, NTE451, oswa 2N4416-lous la nan tèt ou ke se repons la an jeneral-wo frekans mete nan karakteristik sa yo nan anplifikatè a JFET.
eng
Because antennas that are much shorter than 1/4 wavelength present a very small and highly reactive impedance that is dependent on the received frequency, no attempt was made to match the antenna’s impedance–it would prove too difficult and frustrating to match impedances over a decade of frequency coverage. Instead, the input stage (Q1) is an JFET source-follower, whose high-impedance input successfully bridges the antenna’s characteristics at any frequency. Although many different types of JFET’s may be used–such as the MPF102, NTE451, or the 2N4416–bear in mind that the overall high-frequency response is set by the characteristics of the JFET amplifier.