Combining time‐tested techniques with modern electronic components, an inexpensive ionosonde producing high quality records and capable of unattended automatic operation for extended periods has been designed. Four instruments were built at a cost in 1967, exclusive of labor, of $2000 apiece. Three have been operated continuously for five years at a rate of one ionogram every two minutes, being attended but once a week to change the film. One of these ran 23 months with no maintenance whatsoever.
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