RTL-SDR BLOG 1090 MHZ ADS-B LNA
Here is our new high performance low noise amplifier (LNA) for improving 1090 MHz ADS-B reception. The LNA uses a low noise figure high linearity two stage MGA-13116 amplifier chip and three stages of filtering to ensure that strong signals or interference will not overload either the amplifier or SDR dongle.
An LNA can help improve ADS-B reception by reducing the noise figure of the system and by helping to overcome losses in the coax cable and/or any other components such as switches and connector in the signal path. To get the best performance from an LNA, the LNA needs to be positioned close to the antenna, before the coax to the radio.
The gain of the RTL-SDR Blog ADS-B LNA is 27 dB’s at 1090 MHz, and out of band signals are reduced by at least 60 – 80 dB’s. Attenuation in the broadcast FM band and below 800 MHz is actually closer to over 100 dB’s. In the LNA signal path there is first a low insertion loss high pass filter that reduces the strength of any broadcast FM, TV, pager or other similar signals that are usually extremely strong. Then in between the first and second stage of the LNA is a SAW filter tuned for 1090 MHz. A second SAW filter sits on the output of the LNA. The result is that strong out of band signals are significantly blocked, yet the LNA remains effective at 1090 MHz with a low ~1 dB noise figure.
The LNA is also protected against ESD damage with a gas discharge tube and low capacitance ESD diode. But please always remember that your antenna must also be properly grounded to prevent ESD damage.
Please note that this LNA requires bias tee power to work. Bias tee power is when the DC power comes through the coax cable. The RTL-SDR V3 has bias tee power built into it and this can be activated in software. See the V3 users guide for information on how to activate it. Alternatively if you don’t own a dongle with bias tee built in, then an external bias tee can be used and those can be in our store here. Finally, if you are confident with soldering SMT components, then there are also pads and a 0 Ohm resistor slot on the PCB to install an LDO and power the LNA directly.
In addition please remember that this is a high gain LNA. It is expected to be used at the antenna side, with some 3+ db loss expected on the coax. However, if desired, it can still be used on the receiver side. If used on the receiver side or with a low loss run of coax, you will need to tune the RF gain on the RTL-SDR dongle. By default most software sets the RF gain to maximum. We recommend turning the RTL-SDR RF gain down to about 32 dB if connecting it directly to the dongle, otherwise the high input power may overload the dongle causing poor performance.
- Frequency: 1090 MHz
- Gain: 27 dB @ 1090 MHz
- Return Loss: -16 dB @ 1090 MHz (SWR = 1.377)
- Noise Figure: ~1 dB
- Out of band attenuation: More than 60 dB
- ESD Protection: Dual with GDT and ESD Diode
- Power: 3.3 – 5V via bias tee only, 150 mA current draw
- Enclosure: Aluminum enclosure
- Connectors: Two SMA Female (Male to Male adapter included)
46.5 x 32 x 15.6 mm (not including the SMA).
Including the SMA the length is 69.8 mm.
We tested our new LNA against another ADS-B LNA with filter built in that is sold by another company and the FlightAware Prostick+ dongle in an environment with strong out of band signals such as pagers, broadcast FM, DVB-T and GSM signals. The results showed that the RTL-SDR Blog ADS-B LNA gathered the most ADS-B packets. In the tests both LNA’s were connected on the receiver side to be fair to the FA dongle. Improved performance could be achieved by moving the LNA to the antenna side.
Other ADS-B LNA vs RTL-SDR Blog ADS-B LNA Received Messages
FlightAware Prostick+ vs RTL-SDR Blog ADS-B LNA Received Messages