Tag Archives: RTL-SDR

LNA for ADS-B

After having poor performance with my RTL-SDR while trying to receive ADS-B signals I decided I needed an LNA.  I based this design around the BPF420 device and the schematic I found here. With some help from a friend, ended up with the design shown below. Image

By powering the LNA with 5v through the 600 ohm resistor, the voltage is dropped to 3v and the quiescent current is 5mA, improving the noise figure.  The 600 ohm resistor is high enough impedance to block the RF, eliminating the need to wind an inductor.  If you want to power the device through the coax, just remove R2 and remove and jumper C2.  The files needed to have this made by

LNA_layout

The gain of the LNA at 1090 MHz, the ADS-B frequency, is 15.9 dB.  The gain increases at lower frequencies.  To prevent strong out of band signals, like FM broadcast from saturating the amplifier, a filter will be needed.

LNA Gain Plot

LNA Gain Plot

More on the design of the filter to come…

The files for this project can be found on my Github Repository

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