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Page updated May 17, 2007
The HAARP IRI As Described in the EIS
The Environmental Impact Statement (EIS) provides a description of the design
for the HAARP Full size Ionospheric Research Instrument (FIRI or, more simply,
the IRI) at the HAARP Research Station. The following excerpt, taken directly
from the EIS, describes the completed HF transmitter system.
The IRI would consist of 180 crossed dipole antenna elements arranged
in a grid pattern of 12 rows and 15 columns (Figure 2.2-3). The
proposed design for the stacked IRI calls for the low frequency
antenna to be stacked above the high frequency antennas (Figure
2.2-4). The elements would be supported on 66-foot masts mounted on
steel base piles extending 4 feet above the ground and spaced at
Figure 2.2-3. A larger image
(gif Format 12 k) is also available.
Figure 2.2-4. A larger image
(gif Format 20 k) is also available.
The low frequency element is approximately 69 feet long and 52 feet
above the ground (Figure 2.2-5), and transmits 3.2 MW of energy in a
frequency range of 2.8 - 7.6 MHz. The high frequency element is
approximately 55 feet long and 45 feet above the ground and transmits
3.2 MW of energy in a frequency range of 7.3 - 10.0 MHz.
Figure 2.2-5. A larger image
(gif Format 25 k) is also available.
The masts would be guyed at the top and midpoints and anchored to the
base piles of the adjacent masts. A suspended ground screen would
run throughout the antenna grid area at a height 15 feet above the
ground and would extend 40 feet beyond the perimeter antenna masts.
The mesh of the screen would be not greater than 3 feet square.
Fifty-eight additional piles would be required around the perimeter
of the antenna grid to support the groundscreen extension and to act
as antenna mast tie-down anchors. The entire array system would
occupy a foot print approximately 1040 feet x 1280 feet. The IRI
antenna field would be enclosed by a fence restricting access to a
total area of 1,120 feet by 1,360 feet, or 35 acres.
Thirty shelter modules would be distributed evenly along 5 of the
mast support columns within the antenna grid. These modules would
house transmitting equipment used to power the individual antenna
elements. All shelter modules would be approximately 38 feet long by
8 feet wide by 10 feet high supported by a skid frame set on a
post-and-pad or pile foundation.
Note that the total power that can be developed by all of the transmitters is
3.6 MW. The EIS description recognizes that power losses would occur in the antenna
feed lines, matching networks and in antenna efficiency. Therefore, the EIS
discussion assumed the IRI could actually be capable of radiating a total power
of approximately 3.2 MW (or approximately 0.5 dB less).