I’ve recently installed a 1090 FlightFeeder from Flightaware at my local airport. I’ve had a 978UAT for a few months and it is working fine at the same location. I’ve noticed on the local map I can show UAT aircraft on the ground, but not any 1090 aircraft on the local 1090 map. Case this morning: My friend was taking off from the airport and Flightaware never began tracking until the aircraft was >1,200 feet AGL. I figured this was from another receiver somewhere else, because the local map for my 1090 did not show the aircraft until they were >2,000 AGL. I’ve noticed this on many 1090 aircraft. I’m reporting hundreds of flights at altitude, but when they are low near the airport, it’s simply not picking them up. Antennas are at the highest location we had on airport property. Stange… Attached is a screenshot of my map. Departed KGAD, where the Flightfeeder is located, but did not start tracking (as shown) until far south.
Currently an aircraft is doing pattern work at my airport. Showing up on Flightaware, but my FlightFeeder is not picking it up at all. Screenshot of FlightAware.com:
Your feeder could be overloaded. Transponders can output 200W, even on GA aircraft. That is a lot of power for something close.
You could try turning down the gain, however, that may affect range.
You could also try something like an airspy, that has a much larger dynamic range compared to the std rtl-sdr dongle.
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I’m assuming this can be done in the FlightFeeder settings? It’ll be tomorrow before I can make any changes, but I’ll give this a shot. This makes sense!
Yellow FF has a gain control, Blue FF does not.
Yellow FF you’ll need to reduce quite a bit for an airport install, try a value of 30.
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Ok, got it adjusted to 30. We’ll see what happens. Thanks for the input, and had I known it was a gain issue I could have found tons of discussions on the topic. Appreciate the help!
On Yellow FF I have emailed the tech support to turn on the Adaptive Gain, maybe that will work for you too?
It’s not a setting in the display or anywhere else.
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Well I’ve made many adjustments, currently at 15 to be able to track ground aircraft, or more accurately track low flying over the airport… 30 I was still not picking up aircraft around the field, 25 got better, 20 is probably around the sweet spot. My FF antenna is mounted at the highest point at the airport (aside from the beacon.). I’ve got the longest cable that FA would send, with about 1 foot to spare, so I can’t shorten anything. MY UAT works flawlessly, but getting this 1090 dialed in is a chore. I have noticed that my tracking of lower flying aircraft (<10k feet) at a distance had dropped drastically on the gain of 15. Gain at 20 I was still getting ~200-300 overloads a minute or so.
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Because UAT transponders are usually lower power and generally the about same level. Shorter distances.
The ADS-B transponders power varies a lot and that’s why the distance of reception varies a lot too.
To achieve a higher dynamic range of those distances/power levels you just need a better receiver.
That’s why I switched to Airspy receivers. Sure, performance is not cheap, so those cost a bit more than the generic dongle. And usually they like to have a LNA in front of them (at the antenna) - more costs. That also means no pre-built FF box, but rather a DYI solution.
You know, in your situation, it might make sense to invest in buying and setting up another 1090 receiver (Pi, SDR, cable, antenna), and tuning the gain on one of them for your ground and nearby aircraft, and the other for the distant stuff.
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Or split the signal after the Antenna / coax coming from the roof.
Less hassle / less cost. You lose about 3 dB due to the splitter but that’s usually not too big of an issue.
Though of course if it’s super flat and you could have 250 nmi range … you might get 30 nmi less or something like that.
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Good point. I only suggested a separate feeder because they mentioned the existing unit being a FlightFeeder and I figured that the cleanest solution would be to leave that unit untouched.
Well in this case i’m almost certain they don’t mind the antenna being shared 
With a blue FF it’s a bit of a different story (some of them have the GPS signal come in via the main antenna).
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Yep, and it’s an active antenna that is bias-tee powered, and the GPS chip expects to see a particular current draw from the bias-tee, so putting a splitter in without breaking stuff gets complicated.
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Well… at a gain of 20 I’m getting local aircraft RSSIs at -1.4. Aircraft in the traffic pattern are not tracking well at all. Looks like I’m going to sacrifice a lot of distant traffic to lower the gain way down. Not purchasing equipment to have two feeders, so I’ll just have to lower the gain way down and call it a day.
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