Improving ratio of aircraft seen to aircraft with positions?


Hi all.

Just curious if anyone has ideas on how to improve my ratio of aircraft seen to aircraft with positions.

I started off with the FA antennae. That helped boost my numbers.

I added a filter. That helped.

Then I mounted it on the the roof of my house, which bumped up the numbers.

I ran RTL_TEST -P and adjusted the PPM.

After playing around with agc vs max, dump1090-mutability only seems to work well with GAIN=“agc”.

The powered amplifier I added today doesn’t really seem to help much.

Anything else I can try?



It also depends on region. It would help to see the type of aircraft. If you are near to a military airport then you will get a lot of aircraft without position.
During the day I have 800 to 1000 messages per second and my antenna is on my attic. This weekend I will have more messages without position because a pink skyvan goes up and down the whole day.


Is the amplifier the antenna end of the wire or receiver end?


There is not much you can do about this. It depends on the aircraft, not on your receiver. Aircraft without positions are aircraft which are sending Mode S messages but are not sending the ADS-B extended squitter messages that contains positions.

This is where multilateration is useful - it finds positions for those positionless aircraft.


Instead of “–gain-agc” try “–gain -10” That’s --gain(space)-10(minus10)
Works best for my setup.

I use a 4 element colinear in the window of my 5th floor apartment so the pattern is biased in one direction -EAST
I also use a TV LNA I got at K-mart for $10

Running PlanePlotter.


Your ratio is the same as mine: 28.8%.


agc is the same as -10. You’ll see that in /etc/init.d/dump1090-mutability. I find that agc works better for me than max.


OK, I guess the arguments are different in the linux version. I run on a windows PC.

I also tried the max gain setting and got less performance. I even tried stepping down thru the gain settings but couldn’t find one that beat the agc setting. I tried --enable-agc and that was worse than bad.
There are two agc’s on the dongle, one is the tuner AGC and the other is the RTL AGC. The RTL agc can’t be adjusted, it’s just on or off. OFF is the default, I leave it there.

dump1090 ModeS Receiver Ver : 1.10.3010.14

–device-index Select RTL device (default: 0)
–gain Set gain (default: max gain. Use -10 for auto-gain)
–enable-agc Enable the Automatic Gain Control (default: off)
–freq Set frequency (default: 1090 Mhz)
–ifile Read data from file (use ‘-’ for stdin)
–interactive Interactive mode refreshing data on screen
–interactive-rows Max number of rows in interactive mode (default: 15)
–interactive-ttl Remove from list if idle for (default: 60)
–interactive-rtl1090 Display flight table in RTL1090 format
–raw Show only messages hex values
–net Enable networking
–modeac Enable decoding of SSR Modes 3/A & 3/C
–net-beast TCP raw output in Beast binary format
–net-only Enable just networking, no RTL device or file used
–net-bind-address IP address to bind to (default: Any; Use for private)
–net-http-port HTTP server port (default: 8080)
–net-ri-port TCP raw input listen port (default: 30001)
–net-ro-port TCP raw output listen port (default: 30002)
–net-sbs-port TCP BaseStation output listen port (default: 30003)
–net-bi-port TCP Beast input listen port (default: 30004)
–net-bo-port TCP Beast output listen port (default: 30005)
–net-ro-size TCP raw output minimum size (default: 0)
–net-ro-rate TCP raw output memory flush rate (default: 0)
–net-heartbeat TCP heartbeat rate in seconds (default: 60 sec; 0 to disable)
–net-buffer TCP buffer size 64Kb * (2^n) (default: n=0, 64Kb)
–lat Reference/receiver latitude for surface posn (opt)
–lon Reference/receiver longitude for surface posn (opt)
–fix Enable single-bits error correction using CRC
–no-fix Disable single-bits error correction using CRC
–no-crc-check Disable messages with broken CRC (discouraged)
–phase-enhance Enable phase enhancement
–aggressive More CPU for more messages (two bits fixes, …)
–mlat display raw messages in Beast ascii mode
–stats With --ifile print stats at exit. No other output
–stats-every Show and reset stats every seconds
–onlyaddr Show only ICAO addresses (testing purposes)
–metric Use metric units (meters, km/h, …)
–snip Strip IQ file removing samples < level
–debug Debug mode (verbose), see README for details
–quiet Disable output to stdout. Use for daemon applications
–ppm Set receiver error in parts per million (default 0)
–help Show this help