FlightAware Discussions

Do I Need A Filter?

In case of RTL-SDR Blog filter i need to install it as close as possible to antenna, which would require cutting the cable, and the installation of two SMA connectors. Also it requires bias-T power, which i don’t have, because of i use RTL2832 DVB-T receiver…

But in case of FA Filter, there is no need to put filter near the antenna?Isn’t it?

Ideally, but not absolutely necessary. Just look at the FA dongles, they have a pre-amp built-in, and they are not always installed at the antenna.

As for bias-T, you can use a power inserter. I purchased mine on eBay. This is the one I’m currently using:

Again, ideally yes, but not necessary. The important part is to do all the signal ‘hygiene’ before it reaches the receiver.

Yes, that is what you should do.

Flightaware filter does NOT require power or Bias-T, and can be installed either at Antenna OR at Pi, directly connected to the dongle.

You could build your own filter. Not too difficult :wink:
Roll your own interdigital filter


DIY is fun
Nothing can substitute learning by your own error.
Just like Henry Ford said - failure is an opportunity to learn. When you are done, you will be happy you did it.

Happy experimenting. Have fun. :wink:

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… the uputronics saw filter amp cuts out the gsm900 very very good and is by far the best bang for the buck and is supereasy to handle. lots of side by side filter tests here: The Final Filter Shootout


@TomMuc thank you. Your graphs helped for me to make a decision.=)

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So I’m rapidly wearing out my poor Pi and dongles trying different things, antennas, placements, cables, etc.
Not always easy to determine what is helping or hurting my reception as repeatable results are hard to come by with one of my locations.

Here’s a scan- Prostick + with 1/4 wave simple spider, 25ft RG6 Quad. ( no amps no filters beyond the FA stick)

Does anyone know what causes the noise spread every ~1.4 Mhz across the spectrum ? It seems to show up in nearly all the scans I see users post here.

Your scan looks really clear. I have a similar setup to you on one of my units with the below results. Am hoping a filter before the dongle helps.

Has anyone placed their Pro + or another Dongle into a tin to see if the rf interference reduces as well as adding the additional filter? As seen above from my results the two phone towers near me are sending in a lot of noise. Just wonder if that noise is from the Antenna or external to the dongle or both?

Not exactly what you meant, but partial shielding of ProStick by Pepsi can.

Please see below the photo of the Canceiver

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Yes. I bought metal cases (no longer on sale) for the dongles.
The cases made for the regular rtl-sdr dongles fits the FA dongles perfectly.
It seemed to help quite a bit with noise reduction. I do live in an electrically noisy area with lots of cell/mobile phone sites within 150m(500ft). I had to add cavity filters to my setups to make them work well.
This would also reduce the noise from the RPI itself, if it is not in a metal case.

Pity you cant buy them anymore, a Mint tin it is then…

I have just purchased the FA filter so hopefully that will drop ou some noise aswell … if not ill look into a cavity filter…


Hello @abcd567, @Dxista, @TomMuc!
Finally I’ve installed an Uputronics SAW filter!

My ADS-B message rate increased at least by 3 times: from 40-60 to 180-220 msg/sec
But, i still don’t have an ideal route line, even for not so far away aircrafts.

My scan at max gain (49.6 db)


Your scan shows heavy mobile phone signal at 970~890 mhz and 935~960 Mhz. If this scan is AFTER installing Uptonics saw filter then you need a better filter like a cavity filter

I’m have used uputronics amp and FA filter but had same results 970~890 Mhz and 935~960 cell interference
so I bought me 1 of these

this is my results after fitting no cell interference at all

with the triple filter

and the RTL-SDR dongle v3 with bias t

so the best output so far on my journey with ADS-B very pleased

Hi!Could you please provide the link to your dump1090 web-interface?

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You could get rid of mobile signal by:

(a) Using ONLY above SAW filter


(b) Using above SAW filter + Uptronics Tripple Filter LNA

I did the test on pc with rfscan fa pro plus dongle and ads-b filter on 1 of 360radar antenna’s
i did 2 tests 1 without filter and other with it cleared all cell networks interfering with my station
no other amps / filters
but i can do the test again tomorrow im not 100% i did not have triple amp in line but cannot do rfscan on pi so im pretty sure it was just the fa dark blue and ads-b filter