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In this work we summarize the statistics of the so-called 150-kmechoes obtained with a low-power VHF radar operation at the JicamarcaRadio Observatory (11.97 S, 76.87 W, and 1.3dip angle at 150-km altitude) in Peru. Our results are based on almostfour years of observations between August 2001 and July 2005(approximately 150 days per year). The majority of the observationshave been conducted between 08:00 and 17:00 LT. We presentthe statistics of occurrence of the echoes for each of the four seasons as afunction of time of day and altitude. The occurrence frequency of theechoes is ~75% around noon and start decreasingafter 15:00 LT and disappear after 17:00 LT in all seasons. Asshown in previous campaign observations, the 150-echoes appear at ahigher altitude (>150 km) in narrow layers in the morning, reaching loweraltitudes (~135 km) around noon, and disappear at higheraltitudes (>150 km) after 17:00 LT. We show that although150-km echoes are observed all year long, they exhibit aclear seasonal variability on altitudinal coverage and the percentage ofoccurrence around noon and early in the morning.  We also showthat there is a strong day-to-day variability, and no correlationwith magnetic activity. Although our results do not solve the150-km riddle, they should be taken into account when a reasonabletheory is proposed

Statistics of 150-km echoes over Jicamarca based on low-power VHF observations