Poor range performance

[Aero Club Latina]

Dear All,

untill yesterday I used a VRS on windows with a DVTB dongle for feed FR24, my standard range was always around 180 Nm.
Today I moved on raspberry 3, connecting the same DVTB dongle (picture attached) and using the link " "sudo bash -c "$(wget -O - http://repo.feed.flightradar24.com/install_fr24_rpi.sh)" for installation.
The problem now is that my maximum range is 20 Nm, how is possibile? I didn't move the antenna, and if I connect the dongle to the PC the result come back to 180 Nm, then is not an antenna problem.
Here under i report some data that i hope will help you:

pi@raspberrypi:~ $ sudo service fr24feed status
● fr24feed.service - LSB: Flightradar24 Decoder & Feeder
Loaded: loaded (/etc/init.d/fr24feed)
Active: active (running) since gio 2017-05-25 14:50:15 CEST; 1min 59s ago
Process: 542 ExecStart=/etc/init.d/fr24feed start (code=exited, status=0/SUCCESS)
CGroup: /system.slice/fr24feed.service
├─ 644 /usr/bin/fr24feed -- --monitor-file=/dev/shm/fr24feed.txt -...
├─ 693 /usr/lib/fr24/dump1090 --raw --mlat
├─1494 bash -c ping -c 1 '1.africa.pool.ntp.org' 2>/dev/null | hea...
├─1495 ping -c 1 1.africa.pool.ntp.org
└─1496 head -n 1

mag 25 14:50:15 raspberrypi fr24feed[542]: Starting FR24 feeder: fr24feed.
mag 25 14:50:15 raspberrypi systemd[1]: Started LSB: Flightradar24 Decoder &....
Hint: Some lines were ellipsized, use -l to show in full.

fr24feed.ini
receiver="dvbt"
fr24key="xxxx"
path="/usr/lib/fr24/dump1090"
bs="no"
raw="no"
logmode="1"
mlat="yes"
mlat-without-gps="yes"

fr24feed.log
attached

status variables:
ac_map_size="3072"
build_arch="static_arm"
build_flavour="generic"
build_os="Linux"
build_revision="T201704200925"
build_timetamp="Apr 20 2017 09:25:30"
build_version="1.0.18-9"
cfg_baudrate=""
cfg_bs="no"
cfg_host=""
cfg_mpx=""
cfg_path="/usr/lib/fr24/dump1090"
cfg_raw="no"
cfg_receiver="dvbt"
cfg_windowmode="0"
d11_map_size="4"
feed_alias="T-LIRL12"
feed_configured_mode="UDP"
feed_current_mode="UDP"
feed_current_server="83.140.21.68"
feed_last_ac_sent_num="1"
feed_last_ac_sent_time="1495717512"
feed_last_attempt_time="1495716740"
feed_last_config_attempt="1495716739"
feed_last_config_info=""
feed_last_config_result="success"
feed_last_connected_time="1495716740"
feed_num_ac_tracked="1"
feed_status="connected"
feed_status_message=""
fr24key="xxxx
gps_tods="0"
last_json_utc="1495717431"
last_rx_connect_status="OK"
last_rx_connect_time="1495716615"
last_rx_connect_time_s="2017-05-25 12:50:15"
local_tods="47097"
mlat-mode="UDP"
mlat-number-seen="2"
mlat-ok="YES"
mlat-started="YES"
mlat-time-last-ping="1495717505"
mlat-time-last-seen="1495717507"
mlat-time-stats="1495717511"
mlat-uplink-stats="0"
mlat_problem="no-config"
msg_ring_full="0"
msg_ring_length="0"
num_messages="325"
num_resyncs="0"
offline-mode="no"
rx_connected="1"
shutdown="no"
time_update_utc="1495717476"
time_update_utc_s="2017-05-25 13:04:36"
timing_is_valid="1"
timing_last_drift="-0.0012"
timing_last_offset="-0.0014"
timing_last_result="success"
timing_source="NTP"
timing_time_last_attempt="1495717348"
timing_time_last_success="1495717348"
timing_time_since_last_success="609"

What can be the problem? How can I solve it?

Thank a lot.

[Aero Club Latina]

For more information, this is the status....

pi@raspberrypi:~ $ sudo fr24feed status
______ _ _ _ _ _ _____ ___
| ___|| |(_) | | | | | | / __ \ / |
| |_ | | _ __ _ | |__ | |_ _ __ __ _ __| | __ _ _ __`' / /' / /| |
| _| | || | / _` || '_ \ | __|| '__|/ _` | / _` | / _` || '__| / / / /_| |
| | | || || (_| || | | || |_ | | | (_| || (_| || (_| || | ./ /___\___ |
\_| |_||_| \__, ||_| |_| \__||_| \__,_| \__,_| \__,_||_| \_____/ |_/
__/ |
|___/
2017-05-25 17:25:08 | [main][i]FR24 Feeder/Decoder
2017-05-25 17:25:08 | [main][i]Version: 1.0.18-9/generic
2017-05-25 17:25:08 | [main][i]Built on Apr 20 2017 09:25:30 (T201704200925/Linux/static_arm)
2017-05-25 17:25:08 | [main][i]Copyright 2012-2017 Flightradar24 AB
2017-05-25 17:25:08 | [main][i]http://flightradar24.com
2017-05-25 17:25:08 | [main][i]DNS mode: PING
2017-05-25 17:25:08 | [main][i]Automatic updates are DISABLED
2017-05-25 17:25:08 | ERROR
2017-05-25 17:25:08 | [httpd][e]bind function failed, errno: 98
2017-05-25 17:25:08 | [httpd][d]Master thread terminated
2017-05-25 17:25:08 | [main][i]Reader thread started
2017-05-25 17:25:08 | [master][i]Starting processing thread
2017-05-25 17:25:08 | [main][i]MLAT data feed started
2017-05-25 17:25:08 | [reader][i]Initializing reader
2017-05-25 17:25:08 | [mlat][i]Waiting for MLAT configuration
2017-05-25 17:25:08 | [reader][i]Connecting to DVBT receiver via (exe:///usr/lib/fr24/dump1090 --raw --mlat)
2017-05-25 17:25:08 | [reader][i]Connected to the receiver, configuring
2017-05-25 17:25:08 | [reader][i]Configured, processing messages
Found 1 device(s):
0: Generic, RTL2832U, SN: 77771111153705700 (currently selected)
usb_claim_interface error -6
Error opening the RTLSDR device: Device or resource busy
2017-05-25 17:25:08 | [reader][i]Connection terminated
2017-05-25 17:25:08 | [main][i]Terminating child process 3522 with SIGTERM
2017-05-25 17:25:09 | [time][i]Synchronizing time via NTP
2017-05-25 17:25:14 | [reader][i]Connecting to DVBT receiver via (exe:///usr/lib/fr24/dump1090 --raw --mlat)
2017-05-25 17:25:14 | [reader][i]Connected to the receiver, configuring
2017-05-25 17:25:14 | [reader][i]Configured, processing messages
Found 1 device(s):
0: Generic, RTL2832U, SN: 77771111153705700 (currently selected)
usb_claim_interface error -6
Error opening the RTLSDR device: Device or resource busy
2017-05-25 17:25:14 | [reader][i]Connection terminated
2017-05-25 17:25:14 | [main][i]Terminating child process 3541 with SIGTERM
2017-05-25 17:25:19 | [time][i]Time synchronized correctly, offset -0.0017 seconds
2017-05-25 17:25:19 | [main][i]Feed Network client started
2017-05-25 17:25:19 | [feed][i]Downloading configuration
2017-05-25 17:25:19 | [reader][i]Connecting to DVBT receiver via (exe:///usr/lib/fr24/dump1090 --raw --mlat)
2017-05-25 17:25:19 | [reader][i]Connected to the receiver, configuring
2017-05-25 17:25:19 | [reader][i]Configured, processing messages
Found 1 device(s):
0: Generic, RTL2832U, SN: 77771111153705700 (currently selected)
usb_claim_interface error -6
Error opening the RTLSDR device: Device or resource busy

[Oblivian]

By re running the command you are launching it. You forgot to include service in the status command (this recently changed)

Sudo service fr24feed stop
Restart box

Sudo fr24feed start

Monitor visually for a while.

Sent from my XT1092 using Tapatalk

[Strix technica]

my standard range was always around 180 Nm.
Today I moved on raspberry 3, connecting the same DVTB dongle (picture attached) and using the link " "sudo bash -c "$(wget -O - http://repo.feed.flightradar24.com/install_fr24_rpi.sh)" for installation.
The problem now is that my maximum range is 20 Nm, how is possibile? I didn't move the antenna, and if I connect the dongle to the PC the result come back to 180 Nm, then is not an antenna problem.

The apparent contradiction is that you say you're getting some data (ie max range of 20 nm) which implies it's sort of working, and yet the log you posted suggests that dump1090 can't connect to the SDR in which case you shouldn't be getting anything at all.

As Oblivian suggested, you may be running a second instance of feed, which would explain the failure to connect. Always start/stop with the 'sudo service' command, never directly.

Assuming you already are, then do an 'lsmod' and look for the stock Linux DVB drivers. If those are loaded, you need to blacklist them. That link might help, but it might not be exactly right either.

You can 'sudo rmmod' the drivers, but you have to look at the dependencies and remove dependencies in order which can be a nuisance, but perhaps not as much of a nuisance as rebooting after every change.

Assuming this is not the problem, then the difference may be the gain setting (too high or too low). If you're using one of FA's SDRs (the blue or orange ones) then max gain is almost certainly overdriving the receiver, and in my case even autogain doesn't work (where it does in an identical setup with a generic SDR).

That said, I'd be surprised if the stock fr24 installer didn't do something sane with that by default, but maybe something went wrong during installation.

The log implies that --gain is not being set at all, in which case the default (at least in the dump1090-mutability fork) is maximum, in which case you may be overdriving your receiver. But be aware that FR24 use a forked and customised variant of a different fork (ie has a common ancestor with -mutability and so by now has diverged more than somewhat).

I've never experimented with fr24's incarnation and I don't have a second pi to fool around with, so I can only give you generic guidance. In -mutability's fork, dump1090 configuration is usually kept in /etc/default/dump1090-mutability. Setting a gain of -10 is a magic value for one of the two types of autogain the SDR supports. I'm afraid I have no idea how to tweak gain when fr24feed launches dump1090. I manually set everything up in my instance, because I wanted to experiment and to know exactly everything that was going on.

[Aero Club Latina]

Dear Oblivian,

this is the status that i got with range of 39, if i connect the same dongle to windows the range jump to 160. Anyway this is the status....
pi@raspberrypi:~ $ sudo fr24feed start
______ _ _ _ _ _ _____ ___
| ___|| |(_) | | | | | | / __ \ / |
| |_ | | _ __ _ | |__ | |_ _ __ __ _ __| | __ _ _ __`' / /' / /| |
| _| | || | / _` || '_ \ | __|| '__|/ _` | / _` | / _` || '__| / / / /_| |
| | | || || (_| || | | || |_ | | | (_| || (_| || (_| || | ./ /___\___ |
\_| |_||_| \__, ||_| |_| \__||_| \__,_| \__,_| \__,_||_| \_____/ |_/
__/ |
|___/
2017-05-26 14:55:48 | [main][i]FR24 Feeder/Decoder
2017-05-26 14:55:48 | [main][i]Version: 1.0.18-9/generic
2017-05-26 14:55:48 | [main][i]Built on Apr 20 2017 09:25:30 (T201704200925/Linux/static_arm)
2017-05-26 14:55:48 | [main][i]Copyright 2012-2017 Flightradar24 AB
2017-05-26 14:55:48 | [main][i]http://flightradar24.com
2017-05-26 14:55:48 | [main][i]DNS mode: PING
2017-05-26 14:55:48 | [main][i]Automatic updates are DISABLED
2017-05-26 14:55:48 | ERROR
2017-05-26 14:55:48 | [httpd][i]Server started, listening on 0.0.0.0:8754
2017-05-26 14:55:48 | [master][i]Starting processing thread
2017-05-26 14:55:48 | [main][i]Reader thread started
2017-05-26 14:55:48 | [reader][i]Initializing reader
2017-05-26 14:55:48 | [main][i]MLAT data feed started
2017-05-26 14:55:48 | [reader][i]Connecting to DVBT receiver via (exe:///usr/lib/fr24/dump1090 --raw --mlat)
2017-05-26 14:55:48 | [mlat][i]Waiting for MLAT configuration
2017-05-26 14:55:48 | [reader][i]Connected to the receiver, configuring
2017-05-26 14:55:48 | [reader][i]Configured, processing messages
Found 1 device(s):
0: Generic, RTL2832U, SN: 77771111153705700 (currently selected)
Found Rafael Micro R820T tuner
Max available gain is: 49.60
Setting gain to: 49.60
Exact sample rate is: 2000000.052982 Hz
Gain reported by device: 49.60
2017-05-26 14:55:49 | [time][i]Synchronizing time via NTP
2017-05-26 14:55:55 | [reader][w]Setting new UTC offset: 0!
2017-05-26 14:56:08 | [time][i]Time synchronized correctly, offset -0.0009 seconds
2017-05-26 14:56:08 | [main][i]Feed Network client started
2017-05-26 14:56:08 | [feed][i]Downloading configuration
2017-05-26 14:56:09 | [feed][c]Interval: 5s
2017-05-26 14:56:09 | [feed][c]Latitude: 41.5348
2017-05-26 14:56:09 | [feed][c]Longitude: 12.9154
2017-05-26 14:56:09 | [feed][c]GND: YES
2017-05-26 14:56:09 | [feed][c]NonADSB: YES
2017-05-26 14:56:09 | [feed][c]Timestamps: optional
2017-05-26 14:56:09 | [feed][c]Max range AIR: 350.0nm
2017-05-26 14:56:09 | [feed][c]Max range GND: 100.0nm
2017-05-26 14:56:09 | [feed][i]defined 5 servers
2017-05-26 14:56:09 | [stats][i]Stats thread started
2017-05-26 14:56:09 | [feed][n]LIRL12@83.140.21.87:8099/UDP
2017-05-26 14:56:09 | [feed][n]connecting
2017-05-26 14:56:09 | [feed][n]connected via UDP (fd 7)
2017-05-26 14:56:09 | [feed][n]working
2017-05-26 14:56:09 | [mlat][i]MLAT configuration received, service ENABLED
2017-05-26 14:56:09 | [mlat][i]Starting MLAT with preconfigured position: 41.53,12.92,18.0
2017-05-26 14:56:09 | [mlat][i]MLAT bandwidth reduction active, level 1
2017-05-26 14:56:09 | [mlat][i]Configuring UDP connection udp://mlat-1.fr24.com:19788
2017-05-26 14:56:09 | [mlat][i]Registering MLAT station
2017-05-26 14:56:09 | [feed][i]sent 1,0 AC
2017-05-26 14:56:09 | [mlat][i]Registering MLAT station: SUCCESS
2017-05-26 14:56:11 | [mlat][i]No ADS-B time reference available (0/0)
2017-05-26 14:56:11 | [mlat][i]Pinging the server
2017-05-26 14:56:12 | [mlat][i]Stats 2420/2420
2017-05-26 14:56:14 | [feed][i]sent 1,0 AC
2017-05-26 14:56:21 | [mlat][i]No ADS-B time reference available (0/0)
2017-05-26 14:56:24 | [feed][i]sent 1,0 AC
2017-05-26 14:56:31 | [mlat][i]No ADS-B time reference available (0/0)
2017-05-26 14:56:31 | [mlat][i]Pinging the server
2017-05-26 14:56:31 | [mlat][i]Stats 2420/0
2017-05-26 14:56:41 | [mlat][i]No ADS-B time reference available (0/0)
2017-05-26 14:56:51 | [mlat][i]No ADS-B time reference available (0/0)
2017-05-26 14:56:51 | [mlat][i]Pinging the server
2017-05-26 14:56:51 | [mlat][i]Stats 2420/0
2017-05-26 14:56:54 | [feed][n]ping 1
2017-05-26 14:56:55 | [feed][n]syncing stream result: 1
2017-05-26 14:56:57 | [feed][i]sent 1,0 AC
2017-05-26 14:57:01 | [mlat][i]No ADS-B time reference available (0/0)
2017-05-26 14:57:03 | [feed][i]sent 1,0 AC
2017-05-26 14:57:08 | [feed][i]sent 1,0 AC
2017-05-26 14:57:12 | [mlat][i]No ADS-B time reference available (0/0)
2017-05-26 14:57:12 | [mlat][i]Pinging the server
2017-05-26 14:57:12 | [mlat][i]Stats 2420/0
2017-05-26 14:57:13 | [feed][i]sent 1,0 AC
2017-05-26 14:57:19 | [feed][i]sent 2,0 AC
2017-05-26 14:57:21 | [mlat][i]No ADS-B time reference available (0/0)
2017-05-26 14:57:25 | [feed][i]sent 2,0 AC
2017-05-26 14:57:30 | [feed][i]sent 2,0 AC
2017-05-26 14:57:31 | [mlat][i]No ADS-B time reference available (0/0)
2017-05-26 14:57:31 | [mlat][i]Pinging the server
2017-05-26 14:57:31 | [mlat][i]Stats 2420/0
2017-05-26 14:57:36 | [feed][i]sent 2,0 AC

[Strix technica]

Dear Oblivian,

this is the status that i got with range of 39, if i connect the same dongle to windows the range jump to 160. Anyway this is the status....

You may have missed my reply to you but—

Max available gain is: 49.60
Setting gain to: 49.60

—this is probably why. You're definitely receiving messages, but your tuner is being set to maximum gain and is probably being overdriven.

If you were running the -mutability fork of dump1090, you'd be able to look at the mean and maximum signal strength and noise floor, which would tell you your signal to noise ratio and also whether you're clipping at 0 dBFS. I don't know about the fr24-supplied dump1090 (which I understand to be a fork of the MalcolmRobb fork and therefore doesn't support JSON reporting as does mutability's fork), but you might try http://raspberry.local:8000 (substituting the name if avahi's not running or you've changed the pi's name).

I have no idea why this is not normally a problem for others. Maybe there's a strong local signal and you're getting intermodulation noise, in which case you'd benefit from a SAW or cavity bandpass filter. Warning: FlightAware's bandpass filter is too wide to reject all of GSM900, but it's fine if your RF noise source is well away from 1 GHz (eg a local AM or FM radio station).

Either way, the fact that the same hardware works well on your windows box but not on the pi points to configuration. It could also be the version or fork of dump1090 — mutability's fork does some fancy oversampling and phase processing to improve decoding that probably isn't present in the fr24 fork.

My advice to you would be to install Mutability's fork on your pi, find out what gain your windows instance is using and set mutability's gain to that so you can be sure that dump1090 is configured the same way. (A gain of -10 is a magic number that turns on one of two kinds of auto-gain control, but start off with whatever your windows instance uses.)

You may have to fool around with fr24feed's configuration to tell it not to start its own instance of dump1090.

[Oblivian]

If you want a crash course on above.. https://forum.flightradar24.com/thre...-15-dev-on-RPi

[Strix technica]

If you want a crash course on above.. https://forum.flightradar24.com/thre...-15-dev-on-RPi

And in a shameless act of self-promotion, you might also find my Munin plugins useful for monitoring dump1090-mutability.

See also Munin, a system monitoring tool that, together with my plugins, keeps a history of your radar's performance and statistics.

[Aero Club Latina]

Thanks for your answers, can depend from the type of usb dongle that I'm using?

[Strix technica]

Thanks for your answers, can depend from the type of usb dongle that I'm using?

Not all SDRs are of equal quality but, in principle, one generic SDR should be about as good as any other.

The FlightAware SDRs can behave differently because although they're based on the same chipset as the generics (RTL2832 + R820T/2), they have a 20 or 30 dB auxiliary LNA that's of better quality than the standard built-in one. Because of the gain of this LNA, FA SDRs can behave differently from generic SDRs if you have significant intermodulation problems, for example. I can't use AGC at all on my FA Pro+, despite its bandpass filter, because that filter's bandwidth is too wide to attenuate all GSM signals (and there's a cell base station nearby so I'm pretty sure I get quite a lot of intermod noise).

Regardless of variations, your SDR should work the same on windows as it does on a Pi given the same configuration. Try to find out what gain setting the SDR has under windows and ensure that it's set the same on the Pi.

[Aero Club Latina]

Dear All,

First of all thanks for your reply, in the last days I was able to work on the rospbarry and installing dump1090-mutability_1.15~dev I found the way to modify the gain, I tried different value, even agc and max, but the best result arrived with -10.
Of course I didn't solve the problem, the result is still below what I got when the antenna was running on windows with virtual radar (unfortunately I didn't find the way to check the antenna setting on windows). Another think that I find strange, is the cyclicity of the output, there are moment in which I can see a lot of planes, even far, and moment in which is almost blind. Of course the level of traffic around is the same.

In case you have more idea please let me know, I will be really happy to make some experiment to solve this situation,.

Thanks a lot to everybody.