Recently Salil (aka NUCLEARRAMBO) uploaded a blog post on his website detailing how he designed and tested a low noise amplifier (LNA) with a filter for 130 – 160 MHz, which is useful for improving reception for the Meteor M2 LRPT weather satellite. If you were unaware, an LNA can help improve the reception of an SDR by reducing the noise figure of the system, and by overcoming losses from long coax cable runs. The filter helps reduce the strength of out-of-band signals which if too strong, can desensitize and cause imaging on the RTL-SDR.
In his design, Salil used a PGA-103+ LNA chip which has excellent noise figure and OIP3 specifications. His blog post details how he designed the circuit around the PGA-103+, added a bias tee for power, and how he designed the filter.
In part 2 of his post, he details how he tested the LNA+filter combinations frequency response, input voltage range, noise figure, and bias tee with an RTL-SDR Blog v3 and a NanoVNA V2.
