FlightAware ProStick: A new ADS-B optimized RTL-SDR with built in LNA
The FlightAware team have today announced the release of the “ProStick”, an RTL-SDR dongle that they write has been modified for improved ADS-B reception. The new FlightAware RTL-SDR’s main defining feature is that it comes with a built in low noise amplifier (LNA) on the front end. The built in LNA is optimized for the ADS-B frequency of 1090 MHz and has 19 dB of gain with a 0.4 dB noise figure and an OIP3 of +39dB. They claim that the new unit will give a 20-100% performance boost in terms of range for Mode S reception when compared to a standard RTL-SDR.
As the increased gain and amplifier non-linearities can cause overload and intermodulation to more easily occur, the FlightAware team stresses that you must use the new device with a 1090 MHz filter, such as their FlightAware filter. In a previous post we reviewed the FlightAware filter and antenna and found that they performed very well and are great value for money.
The new unit is priced cheaply at $16.95 + shipping on Amazon for US buyers, and $24.95 + shipping on eBay for international buyers.
So far we haven’t seen any circuit photos or news about which LNA chip has been used, but we intend buy a unit and do a review when it arrives.
One criticism about this unit that we can already see is that it should be understood that good RF design teaches us to always place the LNA as close to the antenna as possible to overcome cable loss and keep the noise figure low. Placing the LNA at the antenna vs at the receiver makes a huge difference in performance, depending on how long and lossy your coax cable run is. Furthermore, integrating an LNA into the receiver ruins the system for optimal performance with an LNA placed by the antenna due to the reduced linearity caused by the additional internal LNA. The post at http://ava.upuaut.net/?p=836 explains optimal LNA placement very well. We think that perhaps selling an external LNA and bias tee module would have been a significantly better idea to optimize ADS-B reception. However, the additional LNA should help to reduce the noise figure of the dongle by a few dBs which will result in improved ADS-B reception as long as signal saturation does not occur.
Does this unit have a TCXO? One of the comments referenced a TCXO, but I don’t see it listed on the sale page or in the write-up here on rtl-sdr.com.
Given that some dongles have significant frequency drift, I’m curious how this unit is able to compensate and whether or not it has an actual TCXO?
They wrote in the forums that it doesn’t have a TCXO, but for their application of ADS-B a TCXO is not critical for performance anyway.
Thanks for the reply! I suppose it is because S-mode signals are wide-band enough to not be affected by the drift? I ask because when using the RTL-SDR in an APRS application, a small amount of drift results in no packets being decoded.
Thanks again. I have one on the way, so I’m anxious to test the performance vs. a ‘normal’ rtl-sdr.
Yep they shouldn’t be affected too much by drift since they are wideband. Performance with the ProStock will be about the same as adding an external LNA right after the RTL-SDR. Optimally the LNA should be placed right by the antenna, but placing it by the receiver with a strong filter can also help a bit to reduce the noise figure.
FlightAware should suggest this combination. Their ADS-B antenna, their 1090 filter, their new dongle, and a high quality 33′ USB amplified USB extension cable with ferrite beads. Plus a metal weather proof box to house the filter and dongle. And they need to redesign the circuit to draw much less current than 300 ma. The USB extension was part of my success receiving more than satisfactory 1090 signals with low loss.
What to cut from the tuner to meet bellow 300mA consumption? Just the R820T is drawing 175mA. Plus RTL2832u, oscillator (TCXO), LED …. They need to switch from R820T2 to some other zero IF tuner to lower the consumption. So called “standard” dongle with R820T2 tuner is on 300mA if not higher. Add here +39dBm OIP3 LNA and you should be on 400mA.
Hey Adam! Contact FlightAware with your ideas. I’m sure they will listen. You have shared many great designs on this web site.
Ahhh, I write the answer and lost due to wrong antispam answer 🙂
To keep the answer short, try to find some mmic delivering +39dBm OIP3 and 30-40mA consumption. This must be some joke. NO WAY! That’s +25dbm to +29dBm P1dB. Come on guys, 40mA @5V? Something is missing there 🙂
Did not publish the comparison results. Have to compile a set of screenshots. Your R820T2 experience some increased noise floor in range of 150-400Mhz. Above that your dongle is really quiet comparing the old R820T.
Hmm wonder which spec is wrong then, the OIP3 or the current…
The metal case may reflect some internal noise in those frequencies. Next on the agenda in improvements is to try to reduce the internal noise of the dongle. Or you mean the R820T2 chip has a higher noise floor in that region?
They have the audience for that product. At the end it may work OK. Most probably the idea was to improve the noise figure of the dongle and get 20-30% better performance on that feature which is OK. This can work with the sharp and low loss filter. Anyway, they can always kill the gain in the tuner if the system run into non-linearity. Quickly doing the math if you reduce the gain in the dongle for the gain of the LNA to get better OIP3 the NF will remain the same as you do not have the LNA in front and having the gain of the dongle at max. reducing the gain in the dongle will give you better OIP3 but also will spoil the sensitivity. The signal chain math is always a compromise. What I see as the possible problem is the dongle consumption. You have to count that any device delivering the +39dBm of OIP3 should draw from 80-100mA at least. Add that on top of the dongle consumption and this may be at the USB port limit. My Android phone can handle your RTL.SDR dongle without any problem using just a micro USB 2.0 cable, but i am afraid that this is already the max. Another 100mA will not work….
By the way, following some post on your forum regarding the lower sensitivity comparing to old R820T tuners I made some test and comparison. Found some interesting readings regarding the noise floor…
Yeah it should improve ADS-B performance a bit by improving the NF, but I don’t understand why they didn’t just go straight to an external LNA + dongle bundle. For the current on their site the write it uses 300mA current draw, which is about 30-40 mA above the normal R820T2 current use.
Have you published your results regarding the R820T vs T2 readings? The R820T is becoming end of line soon I think, so soon there won’t be many dongles with that chip in it any more, only R820T2.
Im torn with this one.
Being an amature radio opperator, I know full well how the LNA should be up the mast, not on the dongle. I also know that any computer spews out a ton of RF junk, thus putting something like this near by is just not going to work as expected.
I wonder what other mods they have done other than the LNA?
We ordered one along with a 20 foot USB extension cable and clip on ferrites.
Will give it a test and see how it goes.
Sound like a good application for the NEW CORNING fiber-optic USB 3.0 cables.
Amazon has them, up to 50 meters.
Sorry… those cables have NO DC capabilities.