When I look at my feed it’s health is consistently around 89 being dragged down by PPM offset. My values are typically around -60. From what I can tell this means there is a bit of a frequency different between my site and those nearby. Is this a correct interpretation? Is a -60 a significant difference?
It shouldn't be an issue. Don't think the health is affected by PPM, is it? You can give dump1090 a PPM correction if you want, but it's not really required.
Thanks. I knew I could provide a PPM correction but from what I read it didn't seem required. I just wanted to double check since it was reported as part of the health check.
If you are comfortable with changing the PPM offset, do it by all means, it doesn't hurt. People around you are most likely using temperature compensated higher precision receivers, so it's very likely that yours is offset. (all the FA prostick users have quite the precise oscillator, as well as the rtl-sdr blog version)
I am using the blue FA prostick with the FA antenna, hence I am a bit surprised my PPM offset seems to be a big outlier compared to receivers around me.Mine is in my attic so it is exposed to temperature fluctuations but here in winter they aren't that very large.My receiver is almost the only one in the region with an offset this large. If I wanted to change the PPM offset is the figure from the stats page a good one to use (-59 typically)?
On the FA discussion forum I found a suggestion to run "sudo rtl_test -p". The output of letting this run for awhile is below. If these are supposed to be comparable offsets it is quite different from what the ADSB health is showing. Not sure which I would rely on (the below data indicates I shouldn't change anything, IMO). sudo rtl_test -p Found 1 device(s): 0: Realtek, RTL2832U, SN: 00001000 Using device 0: Generic RTL2832U Found Rafael Micro R820T tuner Supported gain values (29): 0.0 0.9 1.4 2.7 3.7 7.7 8.7 12.5 14.4 15.7 16.6 19.7 20.7 22.9 25.4 28.0 29.7 32.8 33.8 36.4 37.2 38.6 40.2 42.1 43.4 43.9 44.5 48.0 49.6 Sampling at 2048000 S/s. Reporting PPM error measurement every 10 seconds... Press ^C after a few minutes. Reading samples in async mode... real sample rate: 2048003 current PPM: 2 cumulative PPM: 2 real sample rate: 2047981 current PPM: -9 cumulative PPM: -4 real sample rate: 2048009 current PPM: 5 cumulative PPM: -1 real sample rate: 2047650 current PPM: -171 cumulative PPM: -44 real sample rate: 2048022 current PPM: 11 cumulative PPM: -33 real sample rate: 2047988 current PPM: -6 cumulative PPM: -28 real sample rate: 2048283 current PPM: 138 cumulative PPM: -4 real sample rate: 2048037 current PPM: 19 cumulative PPM: -1 real sample rate: 2047675 current PPM: -159 cumulative PPM: -19 real sample rate: 2047995 current PPM: -2 cumulative PPM: -17 real sample rate: 2047994 current PPM: -3 cumulative PPM: -16 real sample rate: 2047995 current PPM: -2 cumulative PPM: -15 real sample rate: 2048007 current PPM: 4 cumulative PPM: -13 real sample rate: 2048318 current PPM: 155 cumulative PPM: -1 real sample rate: 2047994 current PPM: -3 cumulative PPM: -1 real sample rate: 2047993 current PPM: -3 cumulative PPM: -1 real sample rate: 2048000 current PPM: 0 cumulative PPM: -1 real sample rate: 2047669 current PPM: -161 cumulative PPM: -10 real sample rate: 2048006 current PPM: 3 cumulative PPM: -10 real sample rate: 2048314 current PPM: 154 cumulative PPM: -1 real sample rate: 2047990 current PPM: -5 cumulative PPM: -2 real sample rate: 2047682 current PPM: -155 cumulative PPM: -9 ^CSignal caught, exiting!
The data below can only show relative PPM as it has no reference. You can also check the PPM against the GSM band rather easily. But it's not necessary, the health page is accurate if you have the same PPM offset to multiple users, that's no conincidence. They have precise dongles, you don't Edit: yes even for the prostick, either you have one of the very early units without a precision oscillator, or it has degraded over time or it's a defect. Can you link your adsbx.org/sync page?
Sure, here is my sync page. Thanks for your advice. My ProStick Plus was ordered on Jan 23, 2017 so it is about 3 years old. Not sure if that is "old" or not. Those aren't very expensive so I don't mind replacing mine if need be.
No it's syncing fine. Just put in the 50 or -50 PPM offset, i don't know which one you need, just try i guess It's very clear that your dongle is an outlier, that can happen with mass production. Or maybe it was damaged somehow, but even if that it's probably not affecting reception. You have hansolo and mbizzer, those are annoying buggers making the MLAT results bad.
I gave it a ' sudo piaware-config rtlsdr-ppm -58' and rebooted and will watch the sync page to see what happens.
Which image are you on? You might need to edit /etc/default/dump1090-fa instead if you aren't on the piaware sd-card image. If --ppm isn't in there, just add like this: RECEIVER_OPTION="--ppm 58 Leave the rest of the line be.
Apparently the command I ran modified the file you cited as it has “RECEIVER_OPTIONS="--net-bo-port 30005 --fix --device-index 0 --gain -10 --ppm -58"” as the last line. But after an hour nothing seems to have changed on my site stats. Hmm. I did a ‘ps -fe’ and confirmed that dump1090-fa has the --ppm argument.
Try setting ppm to 0, then sudo systemctl restart dump1090-fa Then check pgrep -a dump1090 Should tell you what's going on. Could be the webserver is having some issues as well. Just wait a bit Yeah seems the webserver might be getting an old version of the website it's caching.
ok, I ran through what you suggested and the parameters on dump1090-fa changed as expected (from -58 to 0). No I switched it back to -58 and I guess it is a wait-and-see on the site stats page.
Hmm, now the page seems to be updating. Maybe the offset option isn't working correctly. Can you show the complete output from pgrep -a dump1090
Sure, here it is without my lat and long. 4397 /usr/bin/dump1090-fa --net-bo-port 30005 --fix --device-index 0 --gain -10 --ppm -58 --max-range 360 --net --net-heartbeat 60 --net-ro-size 1000 --net-ro-interval 1 --net-http-port 0 --net-ri-port 0 --net-ro-port 30002 --net-sbs-port 30003 --net-bi-port 30004,30104 --json-location-accuracy 2 --lat my.lat --lon my.long --write-json /run/dump1090-fa --quiet
Well, I got the new FA Pro Stick Plus and installed it. After 30 minutes my site stats still show a PPM offset of around -58. Maybe it will change over night but if not I guess this is a case of needing to just shrug my shoulders and move on.
I get the impression you have a different feeder name maybe? Let's check: grep USER /etc/default/adsbexchange And let's also check the logs for the mlat-client: sudo journalctl -u adsbexchange-mlat --no-pager
