FlightAware Release their Pro Stick Plus: An ADS-B Optimized RTL-SDR with LNA and 1090 MHz Filter Built in
Back in March of this year we posted about the release of the FlightAware “Pro Stick”. The Pro Stick is FlightAware’s ADS-B optimized RTL-SDR dongle. It uses a low noise figure LNA on the RF front end to reduce the system noise figure, thus improving the SNR at 1090 MHz. Because the added gain of the LNA can easily cause overload problems if there are other strong signals around, FlightAware recommend using one of their 1090 MHz ADS-B filters in front of the dongle to prevent overload.
FlightAware have just come out with the “Pro Stick Plus” which is the same as their Pro Stick, but now with the 1090 MHz filter built into the dongle itself. The Pro Stick Plus costs $20.95 USD on Amazon, which is a good deal cheaper than buying the standard Pro Stick ($16.95 USD) plus their ADS-B filter ($19.95 USD), which totals $36.90. Customers outside of the USA can purchase the Pro Stick Plus from seller WiFi Expert on eBay for $29.95 USD.
FlightAware.com is a company that specializes in live air travel tracking. Most of their data comes from volunteers running RTL-SDR ADS-B receivers.
Over on their forums and on Amazon, they announced the device and specs. They wrote:
FlightAware is excited to announce the next evolution of USB SDR sticks for ADS-B reception! The new Pro Stick Plus USB SDR builds on the popular Pro Stick by adding a built-in 1090 MHz bandpass filter. The built-in filter allows for increased performance and range of reception by 10-20% for installations where filtering is beneficial. Areas with moderate RF noise, as is typically experienced in most urban areas, generally benefit from filtering. By integrating the filter into the SDR stick, we are able to reduce the total cost by more than 40% when compared to buying a Pro Stick and an external filter.
Specifications:
- Filter: 1,075 MHz to 1,105 MHz pass band with insertion loss of 2.3 dB; 30 dB attenuation on other frequencies
- Amp: 19 dB Integrated Amplifier which can increase your ADS-B range 20-100% more compared to dongles from other vendors which can increase range 10-20% over a Pro Stick in environments where filtering is beneficial
- Native SMA connector
- Supported by PiAware
- R820T2 RTL2832U chips
- USB powered, 5V @ 300mA
Note that this dongle is only for ADS-B at 1090 MHz, and not for 978 MHz UAT signals, as the filter will cut that frequency out.
Back in April, we did a review of the original Pro Stick. We found its performance on ADS-B reception to be excellent, but only when a filter was used. The low NF LNA theoretically improves the SNR of ADS-B signals by about 7-8 dB, but in reality there is too much gain causing signal overload everywhere, thus making reception impossible without the filter. Rural environments may not need a filter, but in a typical urban or city environment strong FM/TV/GSM/etc signals are abundant and these signals easily overloaded the Pro Stick when no filtering was used. This new Pro Stick Plus dongle completely solves that problem at a low cost with its built in filter.
Remember that if you are using a run of coax cable between the LNA and RTL-SDR, then it is more optimal to use an external LNA, like the LNA4ALL. Only an external LNA mounted near the antenna can help overcome coax, connector, filter and other losses as well as reducing the system noise figure. The FlightAware dongles are the optimal solution when they are mounted as close to the antenna as possible. This is usually the case when running the FlightAware feeder software on a Raspberry Pi.
We hope to soon review the Pro Stick Plus, however we assume it will operate nearly identically to the Pro Stick + FlightAware ADS-B filter combination.
Flightaware could use a spare GPIO pin on the RTL2832U to turn the band pass filter on/off.
So it looks like the insertion losses are nearly identical, but note the difference in frequency range:
The new dongle with built-in filter passes 1075 to 1105Mhz, while the ‘old’ filter unit passes 980 to 1150Mhz. Not sure whether this would have any effect on on usefulness.
Can’t wait to see the reviews! Definitely much cheaper than the old dongle + filter…
Sean, if you live within Radio Line of Sight of ground SSR-/IFF-interrogators every dB of attenuation helps.
Note: All SSR-/IFF-/MLAT/ACAS-Interrogations operate on 1030 MHz just 60 MHz removed, while replies and ADBS are transmitted on 1090 MHz.
Airborne and ground transmitter output power is in average ~500 W with peak up to max. 2000 W, while the airborne antenna gain is just ~5.25 dBi (circular antenna) to 9 dBi (directional antenna) the ground antenna gain of rotating antennas are ~27dBi or >20 dB higher, which can overload the receiver.
Some more information:
At max. 6 ADSB signals a second are transmitted by an aircraft, and were intended for ACAS (Airborne Collision Avoidance System)/TCAS (Traffic Alert and Collision Avoidance System presently version 7.1) which were intended to provide service up to 22NM. SSR, Mode S based systems including ADSB, ACS and MLAT are specified by ICAO in Annex 10 Vol. IV and related documents. Transmissions are to be evenly distributed between a bottom and a top antenna, for aircraft required to have both.
You will very seldomly receive an ADSB signal with the theoretically possible peak EIRP (Effective Isotropically Radiated Power) strength of an signal for a number of reasons:
– due to antenna lobbing of the azimuth and elevation antenna pattern (lobes and notches) the EIRP can be >40 dB weaker then the theoretically possible peak EIRP
– aircraft antenna pattern for the same antenna will vary among other factors on the aircraft fuselage, location of the antenna on the fuselage, other protruding antennas, sensors, flaps…, which all influence the antenna pattern. For signals from the top antenna you can add another >20 dB of attenuation.
– the antenna gain towards your 1090 MHz ground antenna depends on the flight orientation of the aircraft, which is equally probable for flight orientations between 0 to 360° and bank angles of +20° to -20°.
– while your ground 1090 MHz antenna is fixed, it’s pattern has also lobes and notches in the azimuth and elevation antenna pattern.
At worst the aircraft and your ground 1090 MHz antenna will have notches towards each other, which can reduce the signal strength by > 80 dB .
The majority of the signals you will receive on 1090 MHz are not ADSB signals, which as I tried to explain above, be close to or at the min. signal level that your receiver can process.
Depending on your location and your RLOS you will receive much stronger signal, which can overload your receiver, which are
– replies to IFF- and SSR-Interrogations on 1030 MHz.
– DME/N, DME/P and TACAN airborne interrogators and ground transponder reply pulse pairs, pulses from JTIDS/MIDS terminals all above and below 1030 MHz/1090 MHz.
This is why the narrower the filter for your receiver is, the more likely is that your reception is not degrades by any signal outside 1090 MHz. The max. commercial receiver sensitivity is theoretically <-97 dBm.
The optimal bandwidth for a Mode S signal like ADSB is about <=8MHz/-3 dB, <=28 MHz/-40 dB, <=50 MHz/-60 dB, so you see how bad even the newer filter is compared to the optimal filter curve.
I’ve just read the it uses a SAW filter; the same one i purchased on Ali for 2$.
Can the built in filter be bypassed or the Pro becomes usable only for ADS-B?
Just tap in before the filter.
Tap in yours, i buy something else 🙂