Plane Spotters / Flight Radar Thread

[NLPD1S]

Great blog post and a nice time lapse, Feek! Thanks!

I do have a question about your recommendation though; does the RTL-SDR V3 dongle (+ RTL-SDR 1090MHz LNA) really outperform the FlightAware Pro Stick Plus when the FlightAware stick is mounted directly/close to the aerial?


Here are my stats:
]FA
FR24
I ordered a FlightAware Prostick Plus to upgrade the RadarBox Stick which I'll donate to a friend.

I'm looking around for a 18 meter telescopic slimline tower like this one, however the prices of this company go over the roof:

-15 meter: FG 150 5,5/15/3 €4320,-
-15 meter: FG 200 5,5/15/3 €5670,-
-20 meter: FG 200 6,0/20/4 €6580,-
-25 meter: FG 200 6,0/25/5 €7650,-
Wall mount: €830,-
Rotator construction: €860,- excl. rotor

It has to be telescopic for the neighbourhood, convenience (lower it with a winch), and it will be easier to get a building/surrounding permit for it.
There's a lot of resistance against aerial towers over here (I live in a suburb), luckily my neighbours are friendly and cooperative (which can't be said about local authorities).

I guess I better construct one myself because I can get aluminium for reduced prices. Nice project for the end of 2019/begin 2020

 

[Feek]

Yes, I do think that the RTL SDR and the LNA are better than just the FlightAware dongle.

With a receiver, adjusting the gain is important - The default setting of -10 is absolute maximum gain which can be too much and the receiver can get overloaded.

A very clever gentleman at the FA forums has written a script which runs at 02:45 each day and looks at the percentage of strong signals over the previous 24 hours and automatically adjusts the gain up or down to keep them between 1% and 5% which is optimal.

It only works with dump1090-fa. Details and instructions are here. You simply run one command and then forget about it.

 

[NLPD1S]

Thanks again, Feek. started it this morning.
To check whether it works, should I look at dump1090-fa?

sudo nano /etc/default/dump1090-fa

Edit: Checked it, is currently set to 49.6 (I think that is rather high), I'll check tomorrow if it has changed again.

 

[Feek]

To check whether it works, should I look at dump1090-fa?

Yes, that will show you what the gain is.

It's worth checking to see the average of percentage of strong signals.

awk "$(cat /run/dump1090*/stats.json| grep total | sed 's/.*accepted":\[\([0-9]*\).*strong_signals":\([0-9]*\).*/BEGIN {printf "\\nPercentage of strong messages: %.3f \\n" , \2 * 100 \/ \1}/')"

This will reset each time you restart dump1090 so run it now before it resets itself at 02:45 and it'll be really interesting to see what you're currently getting.

 

[Feek]

Edit: Checked it, is currently set to 49.6 (I think that is rather high), I'll check tomorrow if it has changed again.

Yes it is. I'd be really interested to see the output of the command I posted above.

 

[NLPD1S]

Thanks again, Feek!
I almost feel guilty polluting this thread with my gratitude.

Percentage of strong messages: 3.789

Seems to be a good value.
Today, I raised the aerial a bit higher and raised the discone a bit, too.

My wife thinks I'm crazy climbing the roof again and again.

 

[Feek]

That's lower than I expected but you're running a dongle with no LNA so you will need a lot of gain. It'll change when you swap to the Pro Stick Plus.

I'm happy that you're posting here but OcUK is a lot bigger than just this thread. Have a look around, it's a good community.

 

[Feek]

@NLPD1S Can you run the install script again for the gain setting thing please, it's been tweaked slightly.

Once you've done that, you also might like to have a quick look at the config file:

sudo nano /etc/default/dump1090-fa-autogain

I've set mine to a low of 3.5 and a high of 5 as I think that's the sweet spot.

 

[NLPD1S]

Done that last night.
This is the result (edited and set low to 3.0);

#!/bin/bash

low=3.0
high=5.0

ga=(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 -10)

Let me get this right; the script takes a value from ga, checks whether the percentage of strong messages is between 3.0 and 5.0 percent and increases(when lower percentage)/decreases(when higher percentage) the gain to the next/previous step. A sort of AGC with a slow feedback loop. Simple but effective.

Percentage of strong messages: 3.190

Dump1090-fa configuration:

ENABLED=yes

RECEIVER_OPTIONS="--device-index 0 --gain 49.6 --ppm 0 --net-bo-port 30005"
DECODER_OPTIONS="--lat 51.xxxxxx --lon 4.xxxxxx --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"

Still 49.6dB, it seems that the strong signals of nearby GSM (last week they put additional antennas on a building 220m from my house) and FM-broadcast signals are overloading the RadarBox stick. I think I'll put a RTL-SDR ADS-B filter-LNA-filter on the aerial (and get an RTL-SDR V3 or Nooelec Smartee).

 

[Feek]

Let me get this right; the script takes a value from ga, checks whether the percentage of strong messages is between 3.0 and 5.0 percent and increases(when lower percentage)/decreases(when higher percentage) the gain to the next/previous step. A sort of AGC with a slow feedback loop. Simple but effective.

Pretty much, yes. There are some tweaks being made which should keep things in a better state.

"I’ve reworked the script so it saves the relevant stats in temporary files.
That way it will use the percentage that was received the last 24h, even if dump1090-fa was not restarted."

Just run the command again and you'll pick up the most recent version.

 

[NLPD1S]

Clear, thanks again Feek. Right now, I receive about 900,000 position per day/ 3800 air crafts, so it is not that bad.....
Ill be up on the roof upcoming Sunday I guess, after the heatwave has passed.

 

[The Funktopus]

There’s been a 60’s vintage civil-registered Antonov AN-12 coming into Liverpool John-Lennon, roughly once a week for the past couple of weeks now (it’s bloody loud!) from airfields somewhere in North Africa. Past few occasions the departure airport’s been somewhere in Algeria, the name of which escapes me, while today it’s come in from Tangier. Any idea how I can find out what it’s up to?

 

[NLPD1S]

Hmmz... Seems like FM-broadcast signals are very strong at my QTH.

Adding a FM Notch filter nearly doubles the framerate when I'm using my Discone and a FlightAware Plus stick.
I wonder if adding the filter will have an impact on the reception of the collinear aerial, too.

Still tinkering (and enjoying that).

The RadarBox dongle's gain is now set to 48.0, percentage of strong signals 3.3.

Edit: gain 44.5 percentage strong signals 2.748

 

[divebod]

Thanks for all the help - tried dump1090 mutability on my original Pi B running pihole, but I would notice quite a drop in performance of pihole, perhaps as you would suspect. Anyway have moved the pihole onto a new Zero W and it runs perfectly. Dump1090 and Flightaware feed is working on the original Pi B as well. Was hanging on for the Rasp 4 due next year, but find it’s available early . I’ll probably move to a 4 and get some headroom for other things.

 

[Feek]

Just be aware that some of us are having problems with the Pi4 and RTL-SDR dongles at the moment and are trying to find out what's causing it. It seems to work perfectly well with an Airspy or an SDRPlay but it's not talking properly to any RTL-SDR receivers. It's not Buster because I've tried that on a Pi3B and it's working correctly, it's just the Pi4 so far. I'll make sure this thread gets updated with any progress.

 

[NLPD1S]

@Feek I've done some testing on the Discone (because this is the only available antenna for testing on my roof right now)
The FA Prostick Plus gets an average of 325 Frames/s,
The FA Prostick Plus+FM notch filter gets an average of 550 Frames/s,
The RTL-SDR V3 + Triple filter LNA gives an average of 700 Frames/s
Adding the FM Notch Filter to the V3+LNA has no effect.

You mentioned V3+filter LNA would outperform the Blue FA stick and it does by a huge margin.

Still waiting for a pigtail N to SMA I ordered.

 

[Feek]

The RTL-SDR V3 + Triple filter LNA gives an average of 700 Frames/s

You mentioned V3+filter LNA would outperform the Blue FA stick and it does by a huge margin.

You wait until you get the better aerial up, I predict 1,200 messages/second

 

[Nazbit]

Missed those posts about the auto gain script. Will give that a go.

How can I check that d1090 is actually feeding adsb exchange?

Been feeding the other three more or less non stop for 18 months now and I believe I configured adsb exchange at install but without a stats page or anything I don't know how to be certain.

Enjoy their site so want to make sure I'm giving them something back.

Ta

 

[Feek]

How can I check that d1090 is actually feeding adsb exchange?

Easy - click here.

 

[Nazbit]

Perfect. Feeder is detected.

Thanks