It is better to unscrew the whip and use a thin wire as whip, starting length 69mm, then cutting say 2 or 3 mm at a time down up to say 50mm. At each cut, observe for say 30 minutes. Once the best length is known, replace wire by another wire cut to optimum length.
i am located in Germany, and also did not change anything since my move on November 12, but the performance shows some downtrend as well. Checking the other stations around me, they show the same trend, so i am not too concerned.
Interestingly it’s a downtrend in Positions, but not in flights.
The antenna in the picture looks too long. Is that before cutting?
If you look, it seems that only the “other positions” are the ones that dropped, the actual ADS-B ones increased. That’s generally a good thing.
That signal level is REALLY low.
I’d suspect that your antenna cable is broken or something is going wrong.
Let’s also check what gain you have set … :
pgrep -a dump1090
Hi, yes, that was before cutting. Thanks
This is the result, I don’t see anything relating to gain? The below was set with the FR24 wizard. Do I need to change something?
pi@raspberrypi:~ $ pgrep -a dump1090
18531 /usr/bin/dump1090-mutability --net --net-bi-port 30104 --lat removed --lon removed --raw --mlat --write-json /run/dump1090-mutability/
Yeah go back to dump1090-fa, the script below will fix up the fr24 configuration as well: Bundle install for dump1090fa · wiedehopf/adsb-scripts Wiki · GitHub
Not sure which gain mutability uses as default, you want dump1090-fa anyway.
You might need to reinstall graphs1090 due to the different dump1090 or change the collectd.conf.
Thank you for your time and scripts.
I have changed to dump1090-fa and now see the following, and on graphs1090 the signal level has increased significantly. Should I leave like this and see how it performs?
pi@raspberrypi:~ $ pgrep -a dump1090
735 /usr/bin/dump1090-fa --device-index 0 --gain -10 --ppm 0 --net-bo-port 30005 --max-range 360 --net --net-heartbeat 60 --net-ro-size 1000 --net-ro-interval 0.1 --net-ri-port 0 --net-ro-port 30002 --net-sbs-port 30003 --net-bi-port 30004,30104 --net-bo-port 30005 --json-location-accuracy 1 --lat removed --lon removed --write-json /run/dump1090-fa --quiet
That’s the maximum gain now.
(-10 is automatic gain control but due to rtl-sdr driver implementation and the nature of ADS-B signals it’s equivalent to gain of around 58, the next lower setting is 49.6 but without an amplifier -10 is the best setting normally)
The dump1090-mutability ver 1.15~dev’s default gain setting is “max”
The FR24 provide dump1090-mutability ver 1.14’s default gain setting is “-10”
Today my “other” data was also significantly higher than the days before. But simply due to more traffic…
I am not concerned about it.
Let’s see if he reads here - @Humpfrey, are you running an Airspy? I see over 1,800 ‘other’ aircraft on your stats page today!
The data was looking much better after using dump1090-fa instead.
Unfortunately the whole thing crashed and wouldn’t boot any more today, so I’m setting it up again.
I’ve worked on reducing the “Other” AC count in the past weeks.
That’s really good, well done. I didn’t realise it’s possible to switch off options in those charts, that’s useful, thanks 
