What might be causing this drop?

On Saturday at around midnight my site’s numbers and range pretty much halved and have stayed there since. My range is now a small circle around me, as if I had a standard dongle and tiny antenna.

I’ve checked the Pi OS logs, there’s nothing unusual. There were no power issues. Everything is indoors and hadn’t been touched. I wanted to remove the FA filter anyway so on Sunday around midnight, 24 hours after these symptoms appeared, I did that, and also removed the coax and now have everything right under the antenna with the same adapters. I upped the gain for a day and then put it back. It hasn’t improved anything.

It’s a FA antenna > Uputronics SAW preamp powered by USB > Pro Stick Plus > Pi 3B running latest updated PiAware.

Is it possible that the Pro Stick Plus has met its maker and is in the process of failing? Is that a thing for SDRs? I have a Nooelec one I can swap in to test later this week.

Playing with the gain today I am still getting optimum messages per second at the same gain as before, but the RSSI signals are attenuated at both ends – the strongest signals appear much weaker, and the weakest signals, which would have been seen before, now need to be much stronger to be seen and are lost. Changing the gain just makes that bad situation worse.

I think I’m concluding that the Pro Stick Plus is failing and that the gain remains optimum for maximum dynamic range and messages per second, but that the stick’s dynamic range itself has markedly and fairly suddenly decreased compared to its former self.

I welcome any thoughts on that. I will test later this week with the Pro Stick Plus and no preamp (in case the Uputronics is somehow now doing something similar), and I will also test with the Nooelec to see if that helps (even though it has no ADS-B enhancements).

Has anyone else seen a blue stick fail and did it exhibit these symptoms?


Check the RF signal levels. Are they too high or too low. Did your range decrease?
Did a storm hit around that time. Water can get into the antenna or coax.
RF noise is also possible with the Uputronics amps. I have to use mine with cavity filters due to local noise(144Mhz up to 1090Mhz receivers/amps).

Maybe someone around you built an electronic device which impacts your reception. A broken amplifier in the stick can be as well (but very unlikely).

What is confusion is that on the second day the number of messages larger -3dBFS increased. That is normally an indicator if gain is too high.

Yes range vastly decreased, it is like having one of those tiny mag mount indoor antennas. I just have few aircraft centered inside my previously large coverage area. As I said the ends of the stick’s dymanic range have disappeared. I can only get a strong RSSI with the gain right up (which brings all signals there) and a weak RSSI with the gain right down (which takes everything to the floor).

It’s all indoors so no storms. Funny enough I had been testing with the blue FA filter before the preamp and all that did was reduce range and numbers a little, so I was taking it out on Sunday anyway. I will test with the preamp out and also with a replacement non-FA stick, later this week.

Just done a heatmap scan, all looks clean although 1090 does looks very smeared out now, more so than I remember. I’ll find a previous scan later this week and compare.

Regarding the gain, I mentioned that, that was me upping it a couple of notches for a day and then returning it to where it was. I initially thought the higher gain was the cause, then noticed it had happened 24 hours before I touched anything.

The stick does have these marks on it, but it’s had these for over a year. Looks like a component becomes hot and over time it’s discoloured the plastic. Anyone else have that? I wonder if that same part is failing?


The USB stick does have a preamp included and you cannot disable it.

I had a RTL-SDR amp go bad on me about 4 months ago (didn’t notice for a few months!!!). It was still passing the signal through, but my range / plane count and messages were all down because of it. So do check the amp out.

Aye, I don’t expect a replacement non-FA stick to perform as well, but I was referring to the Uputronics preamp there. It’ll be interesting to see what testing reveals.

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Can someone from FA, who knows about the Pro Stick Plus construction, advise please? I know these SDRs can run hot and I’m not concerned by the mark on the case (it’s been running 24/7 since 2017), but it would be good to confirm that yes, they do “wear out” and yes, this does give the performance drop seen.

I was operating the combination for testing purposes (blue FA stick and powered Uputronics). Gave me same results but i had to lower the gain by 15.
I didn’t get more aircraft, because i am limited on geography. No amp can improve that.

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