FlightAware Discussions

Do I Need A Filter?

was hoping to use on pi oh well thanks anyway

Is there anything I can do to help with the above scan? That is with a FlightAware 1090 MHz ADS-B Bandpass SMA Filter plugged in.

And a prostick+ i assume?

If you are in Europe, a dark blue SMA filter might fare better.

Actually with that nasty interference near 1066 MHz, i’d personally try a SAW filter:

There are other makes.
SAW filters have sharper cutoffs and a narrower bandpass than the LC filters from flightaware.
(and the dark blue FA filter is much narrower than the very wide light blue FA filter)

Yeah I have a FlightAware Pro Stick Plus and a FlightAware 1090 MHz ADS-B Bandpass SMA Filter. Which is the dark blue one. (https://thepihut.com/products/flightaware-1090-mhz-ads-b-bandpass-sma-filter)

I am in the UK so yeah Europe - Is the filter you have mentioned not similar to the flightaware dark blue one i have then or are they different in their own ways?

It’s interesting that that’s a frequency of computer memory – I wonder if that’s internal noise from the host (if using a PC) or RF from a nearby machine or via the mains.

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It’s connected to a Raspberry Pi - The next room does have computers in. Anyway, I changed wall socket and also turned off the computers to see if it would make any difference. Re-did the scan and looking at it, it’s pretty much the same.

Where is your antenna located?

Next to the window - I would love to get it outside but it’s a rented house and drilling holes is probably not going to go down well. I’ve also tried putting it in a room at the back of the house and whatever is running at that freq still shows up.

Is it still there if you disconnect the antenna?
Maybe it on the supply to the dongle and not actually being picked up by the antenna at all.
What version of RPi is it?

Sorry for the delay - Re-did my Pi Setup (OS, feeders etc). This is all running on a Raspberry Pi 3 Model B V1.2

With antenna plugged in



Without antenna plugged in

Well, that shows it really is being picked up by the antenna. Just need to find out where it is coming from.
I’m wondering if it might be coming from the pi itself?
Can you try increasing or reducing the distance between the pi and the antenna and see if the level changes?

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so using a filter on the RB Green would be useless right?

Amazon surprised me and I received my RB filter today just few days after ordering it, and while the traffic for the day has practically died I gave the scan a go. Seems that the GSM signals are suppressed better, however I’m seeing these lines all around:

The scan without the filter:

Is this something that matters? I think that the message rate is a tad higher although the range seems a tad lower and I’m getting the feeling that I’m not getting as many Mode S messages from behind the building (running my Pi on apartment balcony), but I’ll keep this on eye for couple days to see if there’s any real change with more traffic.

The RB Green has both an amp and filter built in (as you are aware).
If you are in a particularly noisy environment (to the point of needing more filtering), the RB Green probably isn’t your best starting point.

I’m not suggesting there is anything wrong with the RBG (I have three), but even RB24 describe it as “The ideal starter device ~”


RF Scan of Various Combinations of Dongles, Filter, and LNA



Thanks for the input, guess I’ll just leave it without the filter and run on the little antenna and be happy with what I get instead :slightly_smiling_face:

You will reach a point as most of us where you will never be happy with what you have in this .
There is always a point where you “want more” :wink:


One could argue that due to your site’s location and max range possible, once you filter out all the noise, have your antenna in the best location, and are getting all you can for the given site, there really isn’t much “more” your can do, so wanting becomes rather moot.

Even if you have really gone all in for the best cable, amp, antenna, and sdr, and are getting max range for your terrain, the only “more” you can get is by relocating to a better site on a higher mountain, but that would be a pretty extreme change just to get “more”. :wink:

I guess you could build your own micro satellite, and launch that on one of the SpaceX rockets to get an even higher setup :rofl:

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Can someone help me to identify what can cause that signal at 1100MHz? I’ve tried Google but couldn’t find the answer.

In the USA the frequency space between 960 MHz and 1215 MHz is used for aeroautical navigation.