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Between the HP frequency synthesizer, which generates a maximum of about 80mW, and the solid state power amplifier, is the IPA with its associated power supply. The IPA comprises two modules, both from Down East Microwave. They are both designed for operation at 1296 MHz. The first in line produces up to about 1 watt of signal, and is used either to drive the second module, with about 15 watts of output, or to drive the power amplifier, with about 200 watts of output. A directional coupler at the output of the first module provides a convenient pickoff point for frequency and drive power information.
Although the IPA and the PA both require essentially the same voltage, it was decided to provide separate power supplies for each. That way, if the PA must be taken off line, the IPA can still transmit at the 15 watt level. In addition, measuring the current used by the IPA when driving the amplifier or when both modules are in use provides a surrogate confirmation of normal operation. The IPA uses a Hewlett-Packard 6034L ATE supply (obtained on eBay) which is programmable and provides voltage and current readback. Normal current when the low power module only is a bit over an amp. When the second module is driving the antenna, current is at the 6-amp level.
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this page last updated 4 January 2003
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