Radio spectral observations are carried
out near the village Tremsdorf 15 km south-east of Potsdam (52.284░
N, 13.134░ E, map). A set of four sweep spectrographs (10
sweeps per second) is fed by a system of four different
aerials in the ranges 40 MHz - 100 MHz, 100 MHz -170 MHz, 200
MHz - 400 MHz, and 400 MHz - 800 MHz. We use a pair of
crossed double-logarithmic Yagis, a 10.5 m paraboloid and
two 7.5 m paraboloids. The parabolic aerials are
parallactically mounted. This way we see the sun at all
frequencies as a star - no image resolution is obtained. The
signal is a spatial integral over the radio noise of the
whole sun. Strongest man-made interference is between 85 MHz
and 108 MHz (local UHF radio), 170 MHz - 200 MHz (local UHF
TV) and between 550 MHz and 700 MHz (local VHF TV).
Observing time is as long as possible in the year (summer
about 4 - 19 UT; winter about 8 - 14 UT).
For special observing campaigns two multichannel
spectrometers can additionally be used : the decimeter
spectrograph (multichannel spectrograph, 693 MHz - 740 MHz,
time resolution 10 ms, bandwidth 1 MHz) and the meter wave
multichannel polarimeter (chirp transform spectrograph, 316
MHz - 337 MHz, bandwidth 135 kHz, 10 ms time resolution if
only measuring Stokes I, 20 ms time resolution if measuring
Stokes I and V). The chirp spectrograph can also be
positioned around a central frequency of 236 MHz.
Important (regularly working and solar dedicated) radio
imaging instruments are the
French Multifrequency Radio
Heliograph (images at five frequencies in the range 150 MHz
- 450 MHz) and the
Japanese Microwave Heliograph
in Nobeyama (images at
17 GHz and 34 GHz).