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Review: FlightAware 1090 MHz ADS-B Antenna and Filter

In this post we will review the FlightAware ADS-B Antenna and their 1090 MHz band pass filter. The FlightAware ADS-B antenna is a collinear type antenna, with 5.5 dBi of gain, a rugged weatherproof radome and N-type female connector. It costs $44.95 USD on Amazon for US customers and $54.95 USD on eBay for international customers (plus shipping). They write that they are selling this antenna at cost in order to improve FlightAware coverage.

The FlightAware ADS-B filter is a bandpass filter with a pass range of 980MHz – 1150MHz, ~1.5dB insertion loss and more than 40dB attenuation of unwanted frequencies. It costs $19.95 USD on Amazon for US customers and $24.99 USD on eBay for international customers (plus shipping). Generally it is much cheaper than other ADS-B filter options on the market.

FlightAware.com is a company that specializes in aggregating ADS-B data from contributors around the world. People can contribute by using the FlightAware official hardware, or with a simple SDR, like an RTL-SDR dongle. They display the data on their website as it can be used to help track flight arrival times. A similar company is flightradar24.com.

If you are interested in getting started with ADS-B reception with your RTL-SDR then we have a tutorial here.

FlightAware ADS-B Antenna

The FlightAware antenna is about 64cm in length and about 2cm in diameter. It uses an N female connector and comes included with mounting brackets and U-bolts. It is painted olive green.

In the photo below we compare the size of the antenna against a reference monopole antenna, an RTL-SDR dongle and the FlightAware ADS-B filter. The antenna appears to be very solidly built and of a high quality finish. The antenna is wareproofed with some silicon caulking used around the seams of the endcaps.

Size comparisonSize comparison

The FlightAware ADS-B antenna is a collinear type antenna. Collinear antennas are omnidirectional (receives equally from all directions) and have a higher gain compared to most other omnidirectional antennas, but their radiation pattern is flattened and directed more towards the horizon. This is a good thing for receiving planes that are far away as they will be at lower elevations, but aircraft at higher elevations relative to your antenna may be received poorer. Although, it is likely that any aircraft at high elevations to your position will be closer to you anyway, and thus have a stronger signal making the reduced gain at higher elevations less important. Judging by it’s ~60cm length and it’s specified gain of 5.5dBi, the FlightAware antenna is likely to be a 4 element collinear.

A 4 element collinear generally has positive gain from 0 – 20 degrees of elevation, whereas a simple dipole or ground plane may have positive gain from between 0 – 40 degrees of elevation. A typical commercial jet flys at about 10km. At a distance of 100km this jet would be at a 5.7 degree elevation, and at 10km 45 degrees. Smaller aircraft fly at about 3km maximum, and at 100km would have an elevation of 1.7 degrees, and at 10km 16.7 degrees, so the collinear covers most cases.

If you live in a valley, or have multiple obstacles such as trees or buildings blocking your view of the horizon then the collinear may work worse than a dipole/quarter wave ground plane/folded monopole type antenna. In this situation you’d mainly only be able to receive ADS-B signals from higher elevations, so an antenna with a less flat radiation pattern would work better. See the end of this post for some example radiation pattern diagrams.

Live Testing

In this review we test the FlightAware collinear ADS-B antenna against a reference antenna which is the folded monopole antenna by Adam 9A4QV. We’ve previously reviewed Adam’s antenna here, and we think it is a good low cost (~22 USD), small sized and ESD safe antenna. The folded monopole antenna theoretically has a gain towards the horizon of 3dBi, whereas the FlightAware antenna has a theoretical gain of 5.5dBi towards the horizon. The folded monopole should be similar somewhat similar in performance to a quarter wave ground plane antenna.

The test involved running both antennas next to each other with two different RTL-SDR dongles. The antennas were mounted in a second story window which faced a busy flight corridor and airport. Results were recorded using modesdeco2 for a few hours. Each antenna was connected directly to the RTL-SDR with as little coax cable as possible.

From the results the FlightAware collinear performed significantly better than the monopole.

The maximum range reached with the FlightAware antenna was 232 nmi (430km, 257 miles), whereas the folded monopole reached 190 nmi (351km, 218 miles). The FlightAware antenna also received about 40% more position messages. The maximum possible physical range of ADS-B signals is about 400-600km, so the range acheived is pretty good.

Notice how in the Contacts/Distance graphs that the FA antenna had a huge spike at a distance of 7 nmi, whereas the folded monopole has a dip. 7 nmi was the distance of a nearby international airport. So the FA collinear was able to receive ADS-B messages from aircraft on the ground (0 degrees elevation), whereas the folded monopole was not able to receive ADS-B messages from aircraft so low due to its lower gain out towards the horizon. This helps confirm the theory that collinear antennas receive better out towards the horizon.

SWR Measurements

Here we used a Vector Network Analyzer (VNA) to measure the SWR of each antenna. A lower SWR means that the antenna is better impedance matched to the receiver, and so less of the received signal will be reflected and wasted.

In the SWR test both antennas had excellent SWR at around 1090 MHz, with both Adam’s antenna and the FlightAware antenna being about 1.15. The FlightAware antenna however has pretty poor SWR of ~10 at 978 MHz, so it may not be so good for UAT reception at 978 MHz. Adam’s antenna has a much better SWR of 2.0 at 978 MHz.

La suite est à lire Review: FlightAware 1090 MHz ADS-B Antenna and Filter de : RTL SDR

 

 

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