Review: rtl-sdr.com ADS-B Filtered Preamp

A low-noise amplifier increases received radio signal strength, whereas a bandpass filter only lets a particular range of signals through to the receiver. Combine the two for the best results - rtl-sdr.com's latest accessory does just that for 1090 Mhz ADS-B signals.
Available for $26 including shipping from China from the manufacturer, this review sample (disclaimer) arrived to Ireland in one week.
Main competitors (unnamed in original product announcement, read psecs) are Uputronics' 1090 Mhz Filtered LNA ($45, review), orange FlightAware Pro Stick (review) and FlightAware Pro Stick Plus ($26, review).
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In your hands


Bubble-wrap envelope reveals a small silver brick and SMA-SMA male barrel adapter to connect to SMA - input RTL-SDR dongles and receivers:



Size comparison vs competitors:


Installation


Power via Bias-T only, that means receiver supplying 5 Volts via coax cable. No external power input, so right now, only rtl-sdr.com's V3 (review) and Nooelec's new SMArTee are compatible RTL-SDR dongles - will NOT work with any other RTL-SDR dongle out of the box. Higher class (read: $100 and up) 12-bit receivers such as SDRPlays and AirSpy range have software-selectable Bias-T, go for the SDRPlay RSPA1 for $100 if want 12-bit bliss.
Supplying power in a Raspberry Pi 3 / Linux environment e.g for FlightAware installations has multiple steps, concise guide here with lots of images and the right copy-paste commands.

Positioning


Regular advice is "place LNA / preamp at antenna to overcome coax losses", which is technically correct, as coax will pick up noise from the environment, and preamplifier will amplify this noise at the end of coax. With LNA at antenna, power supplied via coax cable, signal will be amplified and filtered first.
Important mythbusting: you can not overcome coax loss, if a cable loses 3dB of signal, that loss will remain no matter where LNA is placed. You'll see an improvement with LNA at antenna primarily due to less noise pickup (better range / more Total position reports).
Update 21st March 2018. Due to a comment via email I wish to further clarify; placing a high gain, low noise LNA in the reception chain will help mitigating any negative effects of coax loss, but it will not get rid of said coax loss. Coax loss in 50 feet /15 meters of good quality RG-6 is about 1.5 dB, which is not that much, but noise pickup in an urban environment is a much more serious issue.
If dear Reader has more than 30 feet / 10 meter cable connecting receiver to antenna, and uses a Pi 3 as an ADS-B server, please spend the same cash and an hour looking up Power over Ethernet, only a power adapter, cigarette lighter smartphone adaptor (same 5 Volts output) and suitable length of cheap Ethernet cable needed.


Heat


Gets hot. Elevated temperature is the enemy at 1090 Mhz for perfectionists, use heat sinks, thermal pads, or forced air cooling for best results, this LNA is so much smaller than a pro product:



In comparison, Uputronics did not go above ambient room temperature of 20 Celsius / 65 Fahrenheit, as it's much larger with better case heatsinking:



Does heat matter? Absolutely, in the long run, look at radio receivers surviving decades, name President, Icom, Sailor, common denominator is massive heat sinks for heat dissipation.

Testing Setup and Methodology


Two identical ModMyPi Raspberry Starter kits (reviewmanufacturer), sharing pro Jetvision ADS-B antenna (review vs FlightAware antenna). Setup error less than 2% for Totals, for safety, I'd say less than 5% in Totals means identical performance.
No user intervention, latest PiAware image, automatic gain control, write cards (PiAware installation guide here), add Planefinder (guide here), lean back, look at results.
Update March 21st 2018: Coax length to antenna is 2 meters / little over 2 feet, as I wanted to evaluate the filtered LNA versus the competition. By my guesstimate, most ADS-B enthusiasts do not use long lengths of connecting coax between antenna and receiver.

Performance in short: Versus


Any unamplified setup: much better, expect 50-100% more position reports and a significant jump in range.
FlightAware Pro Stick with 1090 MHz Bandpass Filter (around 50 dollars): better.
Flightaware Pro Stick ($26): better.
Uputronics Filtered 1090 MHz preamp ($45 alone): same.


Compared to unamplified rtl-sdr.com v.3


Same V3 receivers on same antenna via signal splitter.
Filtered amplification helps overcoming line of sight limitations e.g. polar plot of house on one side, antenna on windowsill:


Polar plot of amplified and filtered setup, remember, same antenna with splitter:



Clearly, polar plot "fills out", more than 70% position reports, geographical coverage strikingly expanded:



Keep in mind that this behavior is due to amplification and filtering, all competitors exhibit similar characteristics.


v.3 with filtered 1090 MHz LNA versus FlightAware Pro Stick with FlightAware Filter




28,139 vs 24,277 Total reports after 20 hours, 157.10 vs 151.33 nautical mile maximum range.

v.3 with filtered 1090 MHz LNA versus FlightAware Pro Stick Plus




29.28% less Total Position reports, khmm, a Pro Stick Plus costs as much as this Filtered LNA alone...

v.3 with filtered 1090 MHz LNA versus v.3 on Uputronics 1090 MHz preamp


Uputronics is a British company manufacturing pro level ADS-B gear, like walk into a control tower in Europe where anything more substantial than a pigeon lands and technician will know the name.
Indistinguishable performance with auto gain or gain set at 10 to prevent possible overload:



Rtl-sdr.com 25,621 vs Oputonics 25,416 Totals, max range 164.49 vs 164.26 nautical miles.
As close to identical as possible; I leave conjecture on why to self-appointed experts or proper radio engineers, to me as end user, same performance for $20 less.


What I can't test


High noise environment: testing site in the middle of an urban sprawl of 300,000 residents, multiple radio towers within a few miles, yet far from Times Square, Bombay or Tokio.
Long coax runs: some folks use 30-60-100 foot / 10-20-30 meters of coax to connect antenna to receiver. Newsflash again: coax loss is a serious factor at these lengths, google Power over Ethernet if using a Pi 3 as server, will be cheaper than good quality coax.
PC-based setups: too much power use for 24/7/365 operation for amateurs, 12-bit big boys such as SDRPlay and AirSpy all have solutions for Raspberry Pi 3s.

What I tried


Due to small size fits into a metal drinks can:



Why not test against a V3 with Uputronics on a Jetvision antenna?



Visibly less range (max 182.60 vs 172.46 on the best day of two tested), notice how pro gear overcomes line of sight limitations. 30-40 percent less Total reports, but if you only got a V3 and $25 spare cash or $50 altogether, rather than $160, you might manage to live with those numbers.

Choices, choices


Want best ADS-B performance for value, get a FlightAware Pro Stick Plus for $25, cost of this preamp, and that blue stick will be plug-n-play, but somewhat less performance.
If you already own a V3 or Nooelec SMArTee RTL-SDR or any other receiver with bias-T, e.g SDRPlay or AirSpy range, and want to instantly improve ADS-B performance, this LNA is a great and affordable choice.
If you enjoy either a blue or orange FlightAware dongle, whether you should upgrade is down to your wallet thickness, comparative figures above.
Uputronics or rtl-sdr.com? $25 or $45? Uputronics range is tried and tested, runs much cooler, has plug in power so no software wizardry, compatible with all RTL-SDR receivers, build quality and attention to detail is in a different league. For $20 more, yielding essentially the same performance improvement during testing, choose either you can afford, won't be disappointed.

Would I buy one?


Yes, because $25 is unparalleled value for money for a filtered amplified 1090 Mhz preamp with a few foibles - no external power option, concerns about operating temperature and dependability.
No, same money buys a blue FlightAware Pro Stick Plus, which in a Coketanna will be the cheapest plug-n-play high-performance ADS-B setup this side of a healthy bank balance. For $20 more, an Uputronics 1090 MHz Filtered Preamp is the ultimate choice - as always, you get what you pay for.
So should you get one? Yes, $25 to enter the higher echelons of ADS-B performance is money well spent.

6 comments:

  1. What about this preamp with the Flightaware Pro Stick Plus. Does cascading preamps win again like it did in your dongle test?

    ReplyDelete
  2. Pro Stick Plus doesn't have bias-T so it won't be able to power this LNA.

    ReplyDelete
  3. 1. You can see that any preamp does NOT improve the distance due to line of sight limitations. A decent gain antenna, that is not obstructed, cannot be improved anymore. Any "improvements" are just random statistical because of the nature of randomness of planes locations and heights.
    2. The preamp can (totally) compensate for the loss in the cable, while keeping the noise floor at the same level (when preamp at the antenna).
    3. The improvement from the preamp is marked where the signals are present (line of sight), but attenuated by passing trough various materials (wood, gypsum walls, long coax cables). But even then, it cannot compete with an antenna that has no obstacles.

    ReplyDelete
  4. Thanks for the review. Any plan to test it against LNA and filter from LNA4ALL?

    ReplyDelete
    Replies
    1. No. Adam doesn't make his bias-T filter anymore, that and LNA4ALL costs $50 together.
      I got both, exquisite, but market wants price, not performance. Talk to Adam if you want one: http://lna4all.blogspot.com

      Delete