FlightAware Discussions

Change to flight tracking floor of Skyveiw

Has there been a change to the tracking floor from ground level to some AGL setting? One of the aircraft for 39602 didn’t show up until 13 miles out on departure this morning and at some distance on return arrival this afternoon. We used to be able to see them on the ground at our home airport.


No change, Skyview is showing your local data directly.

Since your site appears to be at the airport, you may need to adjust the radio gain setting to a lower value. Strong signals very close to your site could be overloading the receiver and making you blind to them.

The site (39602) was down until I could get back to it. Looks like I lost the USB port the ProStick + was plugged into. I can see airline traffic off KCMH. Current weather is freezing mist and KOSU is closed due to surface conditions.

As for the gain setting, Eric, the unit is set a -10 for the auto gain out of the ProStick. Do you have a better suggested setting to try?

Thanks for your help!


You will need to experiment with it. There are threads in the discussion forum about this. Personally I suggest looking at the RSSI (signal strength) indicator in the detail table view in Skyview. Sort by that column. If you are seeing a lot of values between 0 and -3 or so that suggests your gain may be too high. Try incrementally lowering the gain until you see fewer RSSIs in that range. You should start to see more close-in positions as you lower the gain.

Don’t think of -10 as automatic gain, think of it as a gain of 55 (due to the data nature of ADS-B the automatics don’t really work)

With the blue stick an a good antenna start with 44 and see if your range is still ok, you might need to reduce further.

Some more text on gain from me in this thread:
(Thoughts on optimizing gain)

But the advice above is very good, just wanted to leave the link here for some more reading.

The issue on 39602 has been resolved and here’s what I did to fix it.

Eric’s suggestion of changing the gain setting from -10 (Auto Gain Control) to 44 is almost perfect for my setup. Before I had few aircraft below 7000 to 9000 AGL and can now see the local Police helicopters patrolling at lower altitudes. The weather here right now is not suitable for the small aircraft not certified for none-icing.

My RSSI numbers, displayed by closing the map in Skyview, originally had 30 to 40 aircraft that were in the 0 to -3 range Eric spoke of and it is now down below 5 aircraft. I set it to 44 as wiedehopt suggested.

wiedehopt’s comment and link to (Thoughts on optimizing gain) was a big help and thank you for that reply.

My Unit is an RPi 3B+ running Raspbian Stretch with PiAware installed over the net. These commands using SSH taken from wiedehopts link did the trick. Note: changing the gain setting in the piaware-config file has no effect on this installation.


Raspbian image written to microSD card, then Piaware Add-on Package and dump1090-fa Add-on package installed

(Raspbian image downloaded from https://www.raspberrypi.org/downloads/raspbian/
 Piaware and dump1090-fa Add-on packages installed as per instructions on https://flightaware.com/adsb/piaware/install 4 )

(a) In this example gain is set to 30. Instead of 30 use the gain value you want to set
 (b) Gain is set to 29.7 instead of 30 as shown in last line. This is due to fact that dongle cannot be set to any value, but to one of the permissible values nearest to the value you specify in the gain setting command.

 Open file /etc/default/dump1090-fa in nano to edit it
sudo nano /etc/default/dump1090-fa

Above command will open file /etc/default/dump1090-fa which has following content:
# dump1090-fa configuration
# This is read by the systemd service file as an environment file,
# and evaluated by some scripts as a POSIX shell fragment.

# If you are using a PiAware sdcard image, this config file is regenerated
# on boot based on the contents of piaware-config.txt; any changes made to this
# file will be lost.

RECEIVER_OPTIONS="--device-index 0 --gain -10 --ppm 0 --net-bo-port 30005"
DECODER_OPTIONS="--max-range 360"
NET_OPTIONS="--net --net-heartbeat 60 --net-ro-size 1000 --net-ro-interval 1 --net-ri-port 0 --net-ro-port 30002 --net-sbs-port 30003 --net-bi-port 30004,30104 --net-bo-port 30005"
JSON_OPTIONS="--json-location-accuracy 1"

 In the line starting with RECEIVER_OPTIONS, change the gain value from -10 to the required value. In this example it will be changed to 30.

Line before change:
 RECEIVER_OPTIONS="–device-index 0 –gain -10 --ppm 0 --net-bo-port 30005"

Line after change:
 RECEIVER_OPTIONS="–device-index 0 –gain 30 --ppm 0 --net-bo-port 30005"

After changes are made as above, save changes (Ctrl+o) and close file (Ctrl+x)

 Restart dump1090-fa to implement the newly set gain value
pi@raspberrypi:~ $ sudo systemctl restart dump1090-fa

 Verify that the new value of gain is actually implemented
pi@raspberrypi:~ $ sudo systemctl status dump1090-fa -l

The last line of output of above command will show gain actually set
piaware dump1090-fa[1254]: rtlsdr: tuner gain set to 29.7 dB


For proper formatting of code


Eric Carlson,

With regard to the over gain setting with the default -10 setting, are you seeing any reliability issues with ProStick Plus units? I’ve purchased 4 since June 4th of 2018 and all now have some issue with aircraft reception.

I tried to reorder from the same source purchased in October and they show none available? The gain setting is now 44. The unit now connected only shows 50 to 60 aircraft.

Didn’t want to start a new thread but wonder if anyone else is having this issue.


The gain setting and reliability shouldn’t have any relation.
A signal too strong will not damage the receiver, it will just make reception impossible for that signal.

It is far more likely there is water getting into your coax cable.

Typically if a dongle fails, it fails completely, not gradually.

The change is rather abrupt, did you change any settings or cable in the last 2 days?
If the dongle is not working properly, there might be output in this log:

sudo journalctl -u dump1090-fa -en50 --no-pager

Please could some tell where I find the RSSI indicator (column) in Skyview. I don’t see if for any of my receivers.

Many thanks

Displaying the RSSI in SkyView:

Click on expand sidebar:

Click the column head of RSSI twice so the numbers closer to zero are first:

(from this post Positions Reported)

If you want to have the rssi column displayed while the map is present you need to change the web interface a bit, it is explained in this post: Announcing PiAware 3! (Latest version: 3.7.1)

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Many thanks for the quick reply and guidance. I didn’t know all those data columns existed. It will keep me occupied for quite some time

Thank you!

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Bought a new ProStick with amp only. (Orange). Attached the 1090 filter from previous install and station is back up and running.

Maybe they are getting ESD damage? Would have expected a sudden failure but what do i know :slight_smile:

What other components do you have between the antenna and the stick?

The ProStick Plus units were connected directly to the antenna coax with a F to SMA adapter. The new ProStick has the amp but not the filter so I added a 1090 filter to its installation. The coax is ran through a grounding block to ground. I added a jumper from the F to SMA adapter to the metal conduit outlet box this morning as an extra precaution.

Traffic is down this weekend due to the high winds. We’ll see if it perks back up as the weather clears.

I’m not sure how the failure would look if the internal LNA where to get damaged.

Maybe the GPIO/USB voltage from the Pi is excessive? On the other hand the stick should have its own voltage regulator for the sensitive components.

Really puzzled.

If multiple ones failed maybe you can write ADSBsupport@flightaware.com
Their ADSB lab could be interested to do an autopsy on one or two of your receivers.

Let’s hope this one lasts longer!

I just sent an email to ADSBsupport detailing the station equipment and conditions seen at the various ProStick failures. Thanks for your comments and involvement in troubleshooting the issue.