![[HEATING]](/html/heating/htlogo.gif)
EISCAT's ionospheric Heating facility including Dynasonde
The Heating facility is situated next to the UHF and VHF incoherent scatter radars. See the list of publications that have come out of this facility since its construction in 1979.
Technical Description:
Transmitters
12 linear class AB tetrode valve (or tube for Americans)
power amplifiers of 100 kW continuous rating each, driven by
a 1.5 kW solid state wideband exciter. Minimum pulse length is about 20uS. Any frequency
in the range 3.85-8 MHz can be tuned, but we have been allocated the following:
4.04, 4.544, 4.9128, 5.423, 6.2, 6.77, 6.96, 7.1, 7.953 MHz. The transmitters can be
tuned up either uniformly or to different frequencies in 2 groups of
6, 3 groups of 4, 6 groups of 2, or 12 different frequencies.
Antennas
There is a choice of 3 arrays. Two of the arrays
(numbers 2 and 3) have 6x6 crossed dipoles, resulting in 36 antennas.
They cover the frequency range 3.8-5.7 MHz and 5.3-8.0 MHz.
The gain of these is about 23 dBi
giving a half power beamwidth of about
14 deg and a maximum effective radiated power of 300 MW.
A pair of transmitters is fed to orthogonal antennas on a row of antennas. A third array
(array 1), covering 5.3-8.0 MHz, has a gain of about 30 dBi giving 1200 MW of effective radiated
power (ERP). A pair of transmitters in this array feeds two rows of antennas.
Each row has 12 crossed dipoles giving a total of 144 antennas.
A particular transmitter can be connected to only one particular row
(or pair of rows in array 1), but in any array independent of the other transmitters.
The antenna gain is frequency dependent as shown on this plot,
from which the ERP can be calculated (eg. 85kW x 12 transmitters x gain).
The transmitters feed the antennas through about 50 km of aluminium co-axial
transmission lines.
Control system
Tuning to a new frequency is done by a PC and can take a few minutes. Tilting of the
beam in the north-south plane up to about +/- 30 deg is possible. Power can be
chosen in 2.5% steps of the maximum tuned power, which itself can be less than
the maximum possible. Complicated amplitude modulation formats are possible under
computer or other sources of control. For example a so-called
"SOUSY-switch" is used for ON/OFF modulation
by about 70dB. Modulation frequencies in the range 15-200 Hz with duty
cyles near 50% can not be used due to power supply resonance problems.
The radiated wave can be linearly or circularly polarized with either sense
of rotation. Polarization reversal can be achieved on a pulse to pulse basis.
Accurate timing to within microseconds is possible. Frequency stability is
as good as the GPS-controlled frequency-standard (formerly the EISCAT cesium beam reference).
A digital HF sounder covering ca. 1-30 MHz is also available. This can be run like an
ionosonde or in other modes such as fixed frequency soundings. Spaced receiving
antennas are used. A sample ionogram
shows a "clean" ionospheric trace.
The latest soundings
should be available in near real-time.
There is a list of all soundings
recorded since November 1992 when the computer was upgraded to a PC.
Heating Results
Here are some (old) results from the UK campaign in May 1995.
We also did a test experiment whereby Heating induced scintillations were observed on signals received at Tromso from a Russian satellite.
Other scientific results and events (old):
API technique (Artificial Periodic Irregularities)
ELF/VLF wave generation
The programme and abstracts for the 4th European Heating Seminar held in Tromso in May 1995 is here
Document date: 17/02/93
Document name: ht-specs.doc
Author Mike Rietveld
