SETI League Technical Manual -- Amplifiers
Model MGA-87563 is a two-stage, low-noise RF amplifier MMIC, designed for use in the 0.5 to 4 GHz range at a nominal gain of 12.5 dB. MGA-86563 is a three-stage version, offering higher gain of typically 21.8 dB. Both components claim 1.6 dB noise figure, and can operate from +5VDC power supplies. Their plastic SOT-363 surface mount package is quite tiny (requiring a magnifying glass and small tweezers for placement on printed circuit boards), and the leads are spaced only 0.026 inches apart, requiring great skill in soldering. A 25 watt, small grounded-tip soldering iron, temperature controlled at 650 degrees F, is recommended. You may also have to work under a ring-fluorescent magnifying lamp, and steady hands are a must. Nevertheless, these low-cost (around $2.00) components are ideal as gain blocks in SETI receivers, at all stages except perhaps the first preamplifer. For best performance in those noise-critical stages, a discrete GaAs PHEMT LNA is recommended.
The MGA-86576 is the same circuit as the MGA-86563, but encased in a 70-mil round ceramic Micro-X surface mount package. This MMIC is far easier to work with than the SOT-packaged devices, but is priced higher (in the $8.00 region). SETI League engineers have prototyped a Water Hole LNA with this device. The test circuit measured a flat 23 dB of gain from 1296 to 1660 MHz, with more than 40 dB reverse isolation and a noise temperature under 150 K. This amplifier is commercially available in kit or assembled form.
Further information on these components is available from your local HP sales office, or contact HP Applications Engineer Al Ward (WB5LUA) at (972) 699-4369.
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