Good Evening
Had a massive drop off in data captured -
The system is located in an attic, I’ve replace the SDR stick with a brand new one and nothing has changed. Anyone compiled a list of devices that cause interference as I’m starting to think this will be my next step.
Many Thanks
Have you checked all the software is still running properly? - is local data on tar1090/dump1090 still visible on the map or is that similarly reduced? If that’s also affected then it’s likely to be hardware related. Have any changes been made to software configuration or other feeders installed that might have altered your existing setup?
If you have replaced the sdr dongle already, then look upstream of that - do you have an LNA? Check that it’s still working OK and has power. Try taking it out of line to see if you get any reception with just the antenna. You should at least see something.
Failing that, check the coax and antenna. As it’s not outside, then look for things like rodent damage.
Interference might be a possibility, but for it to come on that suddenly with such a large affect indicates a new and local source. Have you or anyone nearby installed any new equipment? Something like a new phone mast might have that effect if it’s local and overloading the dongle.
Evening.
Yes the services are running, i get some data during peak times of day from what appears VERY short range but at night it’s basically nothing.
I have no LNA and there is a saw filter centred on 1090MHz on the stick.
Will venture into the attic tomorrow with a VNA to check the antenna and cable but the cable from the SDR to the antenna is only 6" long. I might also try and break out the Portapak and search around 1090MHz.
There is no new cell site in the area and we are basically under the main flightpath from LHR to the US.
Is that an external saw filter or built into the stick?
If it is external then it is possible that it has failed.
Looking at the stats it seems to have deteriorated over a few days, I don’t think that is consistent with an interference issue as that is more likely to be an instantaneous drop. It looks to more a deteriorating connection or component external to the stick itself, given that you say you have replaced the stick.
Looks like your stats are coming from the FlightAware online service. Can you check your local system to see if the counts agree with what FlightAware is receiving from you? Is it possible that you have a transient network issue?
No.
Consider the reception fails for whatever reason half way into the day.
Then you will see exactly this in the FA stats:
normal days
1 day half way
bad days
@tballam
do you have an rtl-sdr stick without LNA by chance?
Otherwise it’s likely you need a prefilter.
The SDRs with internal LNA have the filter after the LNA typically.
So the LNA can get overloaded with interference.
Not directly related to this thread, but @wiedehopf’s above question prompted me to post this 2013 photo. This DVB-T was my first SDR which I purchased in 2012, and it is still working great 
. It has no builtin LNA, and no builtin Filter
Click on Photo to See Larger Size
