Second Low Noise Amplifier
The second LNA is located inside the observatory and is the same model 0.8 dB NF 20dB gain unit bought on eBay. This LNA is primarily used to amplify the signal to a level where gain settings of around 30 dB can be used on the following RTLSDR dongle to ensure enough bits of digitisation occur.
At this point in the RF chain an LNA is not needed (as a higher noise figure general purpose amplifier will not degrade the noise figure significantly), but it was available and so was used. The LNA could be replaced by an MMIC amplifier (ERA-5) without significant NF penalty.
NOTE: this 2nd LNA was removed in later activities as it was found that the dongle seemed more stable running at maximum gain (49.6 dB) with Digital AGC enabled and input levels which exercised only about 5 bits of the 8-bit ADC range. This may be entirely a local effect and no statement is made other than what was observed.