Hey all,
Not new to ADS-B but new to anything more than a FA+. I am looking to extend my coverage. And have a FA+ and LMR600 and a DPD antenna. Would love to know everyones thoughts on what I should do next… Part of me leans to a cavity first, part of me leans to the Sawbird+… I know they are 2 different things. Just want some opinions…
Well a cavity filter is better than a SAW filter in terms of both out of band rejection and insertion loss. Of course cavity filters are more expensive than SAW filters and they are harder to find (unless you can build one yourself). You won’t find a 1090 MHz cavity filter on Amazon.
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I was thinking Sysmocom. From what I was reading… I will need a bias tee?
Have you used a cavity on ads?
I have used cavity on other projects (helium) and it worked great. Didn’t have to use a tee tho.
The cavity filter would go between the antenna and LNA (if you use one). The bias tee is for powering the LNA over coax.
I haven’t used a cavity filer for ADS-B. I use an RTL-SDR triple filtered LNA. I think the design of that device was excellent: (i.e. filter a little, amplify a little, filter some more, etc). Unfortunately you can’t buy it any more. Can you buy the Sysmocom filter at this time?
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Cavity Filters are a lot more expensive. And it all depends on your environment. In some cases it won’t increase anything as you are simply limited by your terrain or obstacles. This cannot be fixed by a filter.
Jetvision is also selling a cavity filter. I would assume you need an amplifier in addition.
I am using a combined Uputronics LNA with filter and it works perfect.
The Jetvision filter:
Filter 1090 MHz with SMA-Cable - jetvision Webshop
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Wondering if you know how your Uputronics LNA/Filter compares with the FA Pro-Plus combined with the FA dual band pass filter?
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I am using the sysmocom cavity filter with an orange FA stick. The results are better compared to just a blue FA stick (more messages, same max distance).
But I guess it really depends on your local situation, and I have used an rtl-sdr lna with filter in the past, which at least had comparable results.
The cavity filter does not need bias-tee, and it is not cheap. Any other combination might get you the same results for less money or better results for the same.
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There’s also 1090 MHz cavity filters available on eBay (new) for $70.
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I’m using the “Lothar” cavity filter (available on the airplanes.live store). Definitely not cheap, but a noticeable difference compared to the SAWbirld+ that I used before (I now use the Lana LNA with the cavity filter between it and the antenna). Because of my geography, the increase in range wasn’t spectacular, but I can see a LOT more low traffic around airports that based on HeyWhatsThat I would assume that I shouldn’t be able to see. So again, very faint signals being picked out of the noise (all this is with an Airspy Mini).
Which reminds me - the bigger improvement is likely going to be RTL SDR (like the orange stick) to Airspy and separate high quality filter and LNA)
Ok that Lothar cavity filter on Airplanes.live store is the same one that is on eBay. A little cheaper: $67
Hello
Sounds like you’re ready to boost your ADS-B setup. If you’re looking to extend coverage, both a cavity filter and a Sawbird+ have their benefits.
A cavity filter can help reduce interference, which is great if you’re in an area with a lot of RF noise. On the other hand, the Sawbird+ offers an LNA (Low Noise Amplifier) with a built-in filter, which can improve signal strength and overall reception.
If interference is your primary concern, start with the cavity filter. If you’re looking to boost weak signals, the Sawbird+ might be the better first step. Ultimately, both are great additions and can complement each other well.
Hope this helps!
Thank you
nolanmaris
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This is the 1090 MHz cavity filter that I recently bought. Makes a huge difference in positions reported, but only marginal difference in number of planes seen for me. Your (nautical) mileage may vary. 
In the above linked thread you can also see some heatmaps I took with the Sawbird+ ADSB.
I’ve tested the Uputronics with the blue FA ProPlus device. The only benefit was a lower gain to be set, otherwise the stick would be overloaded with false messages.
There was no further improvement because of my environment.
The dark blue additional filter from flightaware did actually nothing for me, the performance of the FA ProPlus device was identical. I assume because i do not have electronic devices around me which can disturb reception.
My current setup is the Jetvision Airsquitter and the Uputronics LNA. For this setup i need to run an antenna splitter because the GPS signal coming from the antenna does not go through the Uputronics.
So i got this splitter with a cheap GPS receiver and it works perfect.
Best performance i had using a Raspberry 4, an Airspy mini stick and the Uputronics LNA.
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Foxhunter thanks for the detailed feedback. I appreciate your response.
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Curious if anyone looks at the 1090 graphs while modifying their systems for increased performance and actually see any measurable changes in the “Tracks Seen” graph showing “tracks with single message” in pink and “tracks with more than one message” in green? I would like to think you could decrease the single message pink volume.
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Jim thanks for the pointer to the Lothar cavity filter. I installed one inline on my system on Dec 26th this past year and the results have been amazing. I have tried numerous other filters and this is the only one that has provided any positive results. It allows my system to recognize aircraft that were previously lost in the noise.
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