FlightAware Discussions

Do I Need A Filter?

I suspect a cavity filter may be the only way to filter 1100 MHz out. Might even need a bit of retuning to clip the high side a bit more. Also seems like some strong lower frequency signals too. Good luck.

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The plan is to build an interdigital band pass filter and tune it using the “Noise Source” and the ADS-B.
It will be my first time building a filter :slight_smile:

Good times! Not sure if you’ve come across this or not (I think @jerryh47 already pasted it earlier in this thread, but there is a bunch here to sift through), but it could help your design. Keep us posted on your progress.

https://www.changpuak.ch/electronics/interdigital_bandpass_filter_designer.php

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Pro Stick Plus here with integrated filter
I guess I still need another heavy duty filter to get best performance given my graph?
https://i.imgur.com/UQMGC2g.png

Is there any go to recommendation for this kind of heavy noise

I have removed my additional FA filter on Friday.
Since then i do have a little bit improved range of approx 10-20 NM, also the reception has been increased slightly.

Looks like I do not need the filter and my spectrum result was looking pretty much the same as yours.

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My antenna is line-of-sight to the interrogator at BWI 7 nmi distant. When the Interrogator is pointing towards me its 1030 MHz RF pulses desense the AirSpy SDR and/or the LNA, unless I insert the cavity filter between the antenna and the LNA. The cavity filter attenuates by ~33 dB at 1030.
So yes, I need a good filter.

I have added the Jetvision Cavity Filter, results look very good
30min frequency scans directly after each other, maybe a slight influence from dying traffic in the evening, but hopefully not
Click on the image to switch between before and after:
https://slow.pics/c/SuyN7qpK

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Do i need a filter part 2…LOL :wink:

HERE

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