About the Transmitters:
I just posted the HAARP web page address, but realized many don't have
full web access, so here is the page text describing the transmitter.
Dual 4CX10,000s in Class AB as finals driven by "only" a 1KW exciter.
Let see, that's about how many IRF510's??????
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The transmitter portion of the HAARP system supplies Radio Frequency
(RF) power to the antennas. The transmitter
operates between the frequencies 2.8 - 10 MHz in the High Frequency (HF)
portion of the RF spectrum. This frequency
range lies directly above the standard AM broadcast band and below the
VHF Television broadcast band.
The transmitters are contained in environmentally controlled shelters
located within the antenna array, under the antenna ground
screen. Each shelter houses six transmitter cabinets containing two
transmitters per cabinet. Each transmitter cabinet provides
power to one of the antenna elements in the antenna array
with one of its two transmitters connected to the
north-south antenna and the other transmitter connected to
the east-west antenna. Each cabinet is capable of
producing up to 10 kW of power from each of its two
transmitters.
A larger image is also available (23.2 K).
This photograph shows the interior of one of the three transmitter
shelters currently in use for evaluation of the developmental
prototype of the HAARP IRI. High power RF transmitters generally require
a cooling system to remove the heat that is
generated as part of the amplification process. Higher power
transmitting systems often use water cooling for this
purpose. The relatively lower power used in the HAARP
transmitter modules permits the use of a forced air
blower system which is located in the back of the shelter in
this photogtraph. Air from the blower enters the
transmitter cabinets through a floor inlet. Exhaust air
returns to the air handler through ductwork in the ceiling.
A larger image is also available (22.1 K).
This photograph is a close up view of one of the transmitter cabinets
installed at the HAARP site as part of the Developmental
Prototype. The center section of the transmitter cabinet contains a
computer controller and common power supplies. The two
10 kW transmitters are located on each side of the central
rack. Although the transmitters share common power
supplies, they are independently controllable through a high
speed fiber optic interface between the operation
center and the shelter. The operating conditions of each
transmitter are checked by the internal computer and
reported to the operations center on a continuous basis.
A larger image is also available (42.2 K).
This photograph is an internal view of one of the two transmitters
making up a transmitter cabinet. The 10 kW final amplifier is
clearly visible in this photograph, along with the tuning
circuit that is used to match the output circuit to the 50
ohm RF transmission line. The tuning circuit also provides
initial bandpass filtering that is required so that this
design will meet the very strict harmonic suppression
requirements in the HAARP specification. The two
"chimneys" are part of the air cooling system that is used to
remove heat from the amplifier during operation.
A larger image is also available (24.3 K).
To achieve the highest quality scientific results and to satisfy
regulatory requirements, the transmitters used in the HAARP array
have to meet stringent technical specifications. Each transmitter must
produce a spectrally pure signal that is controllable over a
60 dB range extending from a maximum of 10 kW down to 10 milliwatts. To
achieve this, a design was chosen that employs
two 4CX10,000 tubes connected in push-pull and operated in class AB for
a high degree of linearity. (A circuit diagram (4.5
k .gif format) of the final amplifier stage is available.) For low power
operation, the output stage can be bypassed and the
antenna fed directly from the solid state 1 kW amplifier that normally
acts as the driver stage for the final amplifier. The
transmitter low power input circuitry contains a digitally controlled
phase shifter which permits each transmitter in the array to
be set to a specific amplitude and phase so as to produce an arbitrarily
shaped antenna beam.
The HAARP transmitter system must be capable of operating in a manner
that does not interfere with other users of the RF
spectrum. The system specifications require that all transmitter
harmonics and other spurious signals be attenuated or
decreased by at least 80 dB (100 million times) below the level of the
main or fundamental signal. All undesired signals above
45 MHz must be attenuated by at least 120 dB (one million, million
times) and all harmonics and spurious signals in the
frequency range 88 - 200 MHz, must be attenuated by 150 dB or more (one
thousand, million, million times). Measurements
made during acceptance testing confirm that the transmitter meets these
strict requirements.
The following two charts show measurements that were made during the
transmitter acceptance testing compared with the
specification. Both charts are for the transmitter operating at its
maximum rated power:
Transmitter operating at 2.8 MHz.
Transmitter operating at 10 MHz.
HAARP Main Page
Table of Contents
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-- WA8GHZ /5 / "I know the guy who built my radio." Jack /Houston/
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