The Ionosonde was situated at 69° 35' N, 19° 13' E at
Ramfjordmoen near Tromsø, Norway. It was operated by the Auroral
Observatory of the University of Tromsø. Routine operation was one
ionogram every 20 min with a frequency sweep from 1 MHz to 12 MHz lasting
between 2 and 3 min. The instrument was fully digitized and based on a
Hewlett Packard 21MX computer. The main characteristics are summarized
in Table1. Note that the combination of a low power transmitter and complemenary
code transmission made the Tromsø ionosonde equivalent to a conventional
ionosonde with 20 µs pulses and 16 kW peak power. The ionograms are
stored on magnetic tape. A noice discrimination routine in the computer
programme reduced the stored data to less than 10% of the raw data. In
this way one 2400' tape holds about 1300 ionograms, equivalent to the data
of 18 days. For the 100 km altitude region the precision of determining
the height of a sporadic E layer is ± 3 km.
Today, data are transfered to CD-ROM. The tapes were 4-11 years old
when they were read, and we had around 20% data-loss during the process.
Characteristics of the Tromsø Ionosonde (1984-1992)
Transmitter: solid state. 2 kW peak power.
Antenna: inverted log-periodic for both transmission and reception.
Receiver: super-heterodyne with 30 MHz IF.
A/D converter: two 8 bits in parallel.
Pulse modulation: phase-coded complementary code; eight elements of 20 µs
Frequency range: programmable within 1 MHz to 16 MHz.
Frequency sweep: 240 frequencies, linearly or logarithmically distributed in the frequency range.