hat
fwaye a nan eksitasyon an se yon VCO Colpitts. Li se mache soti nan yon regilatè 9V lokal, e li gen frekans lan kontwole pa de varactors tounen-a-tounen, sa ki lakòz loading minimòm e konsa ultra ba bri faz. Yon echantiyon nan siyal la VCO divize desann nan yon prescaler IC ak aplike nan yon chip PLL, ki vin referans li soti nan yon koutim te fè kristal kwats ak divize li desann nan 6250 Hz. se frekans la mete nan mòd binè pa yon plonje switch dis-fason sa a, ki kontwole prensipal pataj la pwogramasyon. Si PLL an ki klete, Q1 switch sou yon pwodiksyon ki ta dwe itilize a enfim anplifikatè nan pouvwa. se Pwodiksyon an faz detektè a chip la PLL filtre ak nivo-deplase pa yon amp op, yo dwe sou fòm piki nan varactors yo kontwòl frekans nan VCO la.
eng
The hearth of the exciter is a Colpitts VCO. It is powered from a local 9V regulator, and has the frequency controlled by two back-to-back varactors, resulting in minimal loading and thus ultra low phase noise. A sample of the VCO signal is divided down by a prescaler IC and applied to a PLL chip, which gets its reference from a custom made quartz crystal and divides it down to 6250 Hz. The frequency is set in binary fashion by a ten-way dip switch, which controls the main programmable divider. If the PLL is unlocked, Q1 switches on an output that should be used to disable the power amplifier. The phase detector output of the PLL chip is filtered and level-shifted by an op amp, to be injected into the frequency control varactors of the VCO.