New Product: RTL-SDR Blog 1090 MHz ADS-B LNA
We're happy to announce the release of 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.
The LNA is currently only available from our Chinese warehouse, and costs US$24.95 including shipping. Please note that the price may increase slightly in the future, and that Amazon USA may not be stocked until March.
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 found fairly cheaply on eBay. 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.
Specification Summary:
- 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)
Dimensions:
46.5 x 32 x 15.6 mm (not including the SMA).
Including the SMA the length is 69.8 mm.
Testing
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.
Checking in SDR# for out of band signals also showed that the RTL-SDR Blog ADS-B LNA significantly reduces those strong out of band signals, whereas the others have trouble blocking them out. Below we show the results as well as some measurements.
Reviews
Conclusion
This RTL-SDR Blog ADS-B LNA can significantly improve ADS-B reception, especially if you are in an environment with strong out of band signals. Even if you are not, the low noise figure design will improve reception regardless.
does the 20dBm level reference a 50 ohm input termination?
Yep 50 Ohms.
I have three questions:
What is the operational ambient temperature range of this unit? I am in west Texas and the antenna is mounted on a mast while the Pi is in an enclosure connected via 25′ of LMR400, so the LNA will be mounted on the mast (on the north side of the mast to shield from direct sunlight), and it has been steadily 100+ degrees out here.
I have a gas tube on the antenna and am wondering if it being grounded would affect the bias-t negatively.
Does the bias-t stay enabled after reboots, and if not would a cron job run @reboot be sufficient to enable it before piaware starts running and locks out the command?
Nevermind on the last question, I found the answer here:
https://discussions.flightaware.com/t/enable-biast-on-rtl-sdr-v3-before-dump-fa-piaware-start/20046/16
Max rating for the LNA chip is 150C, so at 37C + say 20C heat at most generated by the circuit you should be fine. Just keep it out of direct sunlight. Note that the LNA isn’t weatherproof, so you’ll need to put it into your own weatherproof box.
Gas tubes typically turn on at much higher voltages. The bias tee is 4.5V, so it shouldn’t turn on the gas tube. There is also a smaller gas tube inside the LNA itself.
Check out this post, and the comments for notes on enabling the bias tee https://www.rtl-sdr.com/getting-the-v3-bias-tee-to-activate-on-piaware-ads-b-images/.
Specs say: “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”
What exactly is the insertion loss of this high pass filter?
Thanks!
JohnnyBravo
Less than 0.5dB. Around 0.2 to 0.3 dB.
Any recommended weather proof enclosure for this amp?
I live within 200m of a phone mast/tower. I get very strong signals within 930-960MHz (ish) which heavily affect my ADS-B reception, even with the blue, round flightaware filter. Is this filtered LNA any better at reducing these signals compared to the blue, round flightaware filter?
It is here. We have 3 towers around here! I had a blue filter before, and this lna / filter combo is far better.
Increased the range dramatically (Up to 400km now, less than 250km previously) and I can now “see” aircraft on the ground 6km away at the airport.
Highly recommended.
Are there any figures available for out of band rejection with this filtered LNA?
I have problems with strong local cellphone signals around 960MHz and wonder how much the filters would attenuate these transmissions.
I added a VNA scan to the image slider (not a very accurate scan though). But basically it’s similar to the simulation. You could expect about 50dB attenuation at 960 MHz.
Thanks that’s pretty impressive. I ordered the LNA from China a few days ago so now I’m really looking forward to trying it out.
Hi everyone.
Can you tell me if an Airspy R2 can drive the 150 ma that is needed for this LNA.
I dont know the maximum current that is available at the bias-tee of an Airspy R2 .
Thanks in advance.
They mention a lower current in their documentation, but it actually can handle 150mA without issues.
Everyone knows ADS-B amps need to go at the antenna for best results and yet barely anyone produces equipment built into waterproof boxes with N connectors, why?
You should conside repackaging the amp in a pole mounted water proof encloser with N connectors. An amp should be mounted near the antenna to be most effective and commercial antennas all have N connectors.
Done and quite an improvement in performance overall 🙂
Totally agree!
I bought one of these along with my RTL_SDR to recieve 402 MHz , didn’t read the specs properly and have found out it’s useless. Is there a way to rip off the filtering? . no Intention or receiving 1090 ever!!! , otherwise it ends up in the junkbox.
It’s only for 1090 MHz ADS-B. All the filtering inside is designed for that. You could desolder the two SAWs and the front end HPF, but i’m not sure what the performance would be like.
Well, have been using this LNA for about a week now.
Results are brilliant! A year ago I got up to 250km with no LNA.
Over the last year with new cellular frequencies, and surrounded by cellular sites,
my range dropped to under 200km. Now I regularly get up to 400km!
Running:
FlightAware Green Antenna on top of 6 metre pole
4 metres RG6
RTL-SDR.com ADS-B preamp ( https://www.rtl-sdr.com/new-product-rtl-sdr-blog-1090-mhz-ads-b-lna/ )
10 metres RG6 to Bias-Tee injector fed from 5VDC plugpack
Short SMA lead to FlightAware Blue Dongle
Dongle plugged into a RPI3
Simply BRILLIANT.
I’ve even bought a spare to play with on another antenna / V3 Dongle / RPI etc.
Well done by the RTL-SDR.COM team.
Murray what version of 1090 are you running??
Hi
This one: https://github.com/mutability/dump1090
I don’t feed anyone. Not planning to.
Stupid question, which side does the rtl-sdr dongle go on, is it on the “out +5v” side??
Yep, dongle connects to the “Out +5v” side because the signal comes out of the LNA and into the dongle there. And that’s where the bias tee voltage comes in too. “In” refers to the signal coming in from the antenna.
Question
What is the max input let’s say the antenna has 10 dB – like the Russian A-10 for example.
Can someone have problems using this LNA with that antenna?
Max RF input allowed by the LNA chip is 20dBm, but the limiting factor is the max allowed by the dongle which is 10 dBm. So taking into the account the 27dB gain of the LNA, aim for -17 dbm max input to the LNA to avoid damaging the dongle.
So worst case with perfect rad pattern alignment, a powerful 10dBi gain antenna, and a large aircraft transmitting ADS-B at max 500W power, as long as you’re more than ~350m away from the ADS-B transmitter you won’t damage the dongle.
You state the Lna needs to as close as possible to the antenna, before the coax. What limts of coax length before your power supply from the dongle starts to be affected.
take a look here
http://chemandy.com/calculators/round-wire-resistance-calculator.htm
But you can also use an bias-tee with a laboratory type power source…..
And much easier
http://www.calculator.net/voltage-drop-calculator.html
Why isn’t an unfiltered LNA offered by RTL-SDR Blog? This would be useful to everyone as we can get filters elsewhere (eBay, Ali, etc.) to pre-filter the RF before it hits the LNA. Bias-t powered, packed inside an enclosure like the ADS LNA, and priced around $25 would surely sell like hotcakes!
We do currently have an unfiltered LNA in the works now. It should hopefully be ready in 1 to 3 months.
We started with the ADS-B LNA because that really should be a separate product by itself and we didn’t really see any high performance yet affordable ADS-B LNA’s on the market until ours. And ADS-B is one type of signal that people really have fun trying to optimize.
For ADS-B it’s very desirable to have the filtering placed AFTER the LNA, because of the high insertion loss degradation that a sharp filter can bring at the ADS-B L-band frequency. But then the problem is that the LNA itself can overload without pre-filtering. So we did a really careful ADS-B specific design that ensures no overloading of the LNA (very low insertion loss pre-filter + high OIP3 dual stage LNA), whilst maintaining a high NF metric, and still having sufficient post-filtering (filtering in between the dual stage and after) so that the dongle doesn’t overload. That would be a more difficult and more expensive to do with a general unfiltered LNA and external LNAs. The idea is that this LNA can be used in almost any RF situation so users don’t need to worry about overloading and NF optimization problems.
Also there are already many cheap unfiltered LNA’s available on the market. But we’ll be bringing one out that’s a little more expensive than those $8 eBay ones, but overall better as it will come in a metal enclosure, will have bias tee power and additional ESD protection available.
Great to hear about the LNA in development. You are right that there are many cheap eBay LNAs out there, but none come in a case. The LNAs that do come in a case are normally professional / commercial grade and cost nearly $200 per.
You’ve brought up some interesting points however. The signals that I am wanting to amplify are ATCS with NFM frequencies in the 896.8875-897.9875 MHz and 935.8875-936.9875 MHz ranges. These are fairly close to the 1090 MHz ADS-B, so I hope I don’t run into the same issues that required pre, mid, and post filtering. I was going to do pre-filtering only.
You should be okay, but you should check first if post-filtering works well or not. If post-filtering is not good and the LNA overloads you always try buy/build a low loss high pass filter for the pre-filter, and see if the LNA still overloads or not. Of course this depends on how much time and effort you really want to spend optimizing the signal.
Starting voltage about 0.6 V
power 180 ma
What are the plans for availability on the European market? Could not find it at any of the “usual suspects” sources.
It’s available from our webstore shipped from China. That way we can ship all over the world.
Is there any plan to create a wideband version of the LNA ?
Received mine, delivered direct from China to the UK. Took just over a week (with tracking too), which was quicker than I expected.
My Raspberry Pi system has gone from tracking 73 flights without the LNA to 131 with it whilst testing this afternoon (a Saturday around Heathrow, London). That’s over 75% increase in coverage. Messages received increased from around 670/s to 1110/s, giving an increase of over 68%.
I was running an ADSBexchange image from their forum, so enabling the bias-tee took a bit of fiddling, but I got there in the end. I had to follow the instructions on the RTL-SDR V3 info page, and make sure I added the enable code line to the very first script that runs. The bias-tee will not enable if the dongle is actively being used by a running program, so you have to get in there first with the ‘enable’ instruction before they start running!
Also, I don’t think it mentions in the write-up, but there is an LED inside the aluminium case of the LNA which will indicate if it’s powered or not.
Just received mine in the mail today, removed a satellite inline amp (was getting power from DirecTV injector) and the Flight Aware filter and put this amp in its place. So far so good but today is Saturday, a bad day to compare. I noticed the Airspy Mini was drawing 270 mA and with the built-in bias tee and the rtl-sdr amp it is now drawing 430 mA.
What are my options for power if I don’t have bias tee? Do you have an injector available?
If you have a V3 dongle then there is already a bias tee built in. If you have a dongle without a bias tee then you can get a cheap external one (power injector) from eBay. e.g. https://www.ebay.com/itm/172460255780?rmvSB=true
the gain depends on the voltage 3.3 V and 5 V?
The gain and other specs may be reduced a bit when running at 3.3V.
I’m really wondering what that “other LNA” was 🤔
Just some random chinese one or the Uputronics filtered LNA?
Don’t want to bash the competition, but it was a PGA103+ LNA with filter after the LNA built in.
Will this also work for UAT on 978 MHz? The flightaware+ filter has a sharp cut off that prevents usage on 978.
No sorry, it’s for 1090 MHz only.
It’s really wise to create a new product with a near-discontinued chip? (MGA-13116). Broadcom catalog say it will be discontinued soon, to not use in new designs.
Yeah unfortunately they just released the obsolescence note in December 2017, and we’d already finished the prototyping and had bought the chips just before then. But the chip stock we have now should be enough for at least 1-2 years as I don’t expect the demand to be super high.
will we have a 137 mhz version for NOAA and Meteor RX ?
Something like this is planned, but not started yet 🙂