Guidance on "sig" column running view1090 --interactive

A few days ago I added an in-line amp and power injector and noticed that the signal level when I run view1090 is now generally in the 120-160 range (never below 100) whereas before the amp the value was fairly low, around 20-60.

I continued to use “–gain -10”. What is an acceptable signal strength range and should “–gain -10” still be a good choice ? I am testing currently a setting of --gain 40.0 and most of the sig values are now in the 20-60 range again, although a few strong ones above 100.

Looked everywhere I could think of but couldn’t find any documentation for the acceptable/possible range of values for “sig”. Also don’t want to overdrive and produce nasty signals.

Thanks for any help.

As I understand it, gain -10 says “use the automatic gain control” and is the recommended setting.

Range, go to website heywhatsthat.com
do “new panorama”
put in the exact location of your antenna (you can tweak this on the map) and your antenna height
give it a name then set it working

when it comes back select ‘in the air’ (top right of map) and set the distances at the bottom to 10000 and 38000

zoom out

This shows you what you should be able to receive if there are no trees or buildings in the way (it takes into account hills, etc)

If you are far short of the distance - then come back with antenna notes and pictures - see what’s suggested

By the way, it usually makes a huge difference putting the antenna above roof height.

That’s been my understanding all along and what I have generally used.

However have no way of interpreting the values for "sig’ (signal level) as reported by view1090 and especially the greatly increased values after adding the amp.

From the New Anomalies Messages Thread http://discussions.flightaware.com/post179654.html#p179654

If you’re running dump1090-mutability, look at the signal level stats it produces periodically to the logfile; they are converted to dbFS (so 0dB is the maximum value of the scale)

I’m running DUMP1090 Mutability 1.15dev with gain set to -10

How do I read this log fragment to tune my settings?


Statistics: Thu Aug  6 16:25:55 2015 UTC - Thu Aug  6 17:25:55 2015 UTC
Local receiver:
  8640135168 samples processed
  0 samples dropped
  0 Mode A/C messages received
  72119106 Mode-S message preambles received
    43551019 with bad message format or invalid CRC
    24254511 with unrecognized ICAO address
    4130942 accepted with correct CRC
    182634 accepted with 1-bit error repaired
  -6.9 dBFS mean signal power
  -0.5 dBFS peak signal power
  387457 messages with signal power above -3dBFS
Messages from network clients:
  0 Mode A/C messages received
  144212 Mode S messages received
    0 with bad message format or invalid CRC
    0 with unrecognized ICAO address
    144212 accepted with correct CRC
    0 accepted with 1-bit error repaired
4457788 total usable messages
137 surface position messages received
343947 airborne position messages received
336626 global CPR attempts with valid positions
4 global CPR attempts with bad data
  0 global CPR attempts that failed the range check
  0 global CPR attempts that failed the speed check
519 global CPR attempts with insufficient data
6428 local CPR attempts with valid positions
  6298 aircraft-relative positions
  130 receiver-relative positions
1026 local CPR attempts that did not produce useful positions
  851 local CPR attempts that failed the range check
  106 local CPR attempts that failed the speed check
0 CPR messages that look like transponder failures filtered
1193971 non-ES altitude messages from ES-equipped aircraft ignored
478 unique aircraft tracks
128 aircraft tracks where only one message was seen
CPU load: 34.9%
  912531 ms for demodulation
  300777 ms for reading from USB
  43583 ms for network input and background tasks


These are the interesting bits for tuning gain:

Mean and peak should be fairly selfexplanatory.

I generally aim for the “signal power above -3dBFS” count to be no more than 1-2% of total usable messages as a rule of thumb. These are strong signals that are in danger of clipping. If you are seeing a lot of them, then you may be losing some messages entirely due to over-amplification.

I’d try decreasing the gain a little and see if that improves the message rate.

PeterHR,

Incredibile site. Thanks for making me aware of it. Recently contemplated creating a profile because of our difficult location in a valley. Glad I didn’t do that as this was far more useful. The map pattern predicts very accurately my directions and distances. Don’t log a lot of planes but even receive slightly beyond the predicted southeastern range well into the state of Chihuahua, Mexico. My profile is named “Limestone ADSB”

The only reason I was attempting to set a discrete gain value was that the 'sig" values jumped considerably after adding the amp and I need to determine if the signal is too hot.

I am comfortable that things are going well based on the profile.

Thanks again.

But Obj’s observations on my gain setting suggested I could do better though I had a reasonable range match to heywhatsthat…

But Obj’s observations on my gain setting suggested I could do better though I had a reasonable range match to heywhatsthat…

I’m not running dump1090-mutability at the moment but rather the piaware image so can’t investigate my signal quality other than through more conventional means.

Guess we’ll always want to squeeze a little more out of the system.

BTW, it’s a streak of laziness than I haven’t re-tried dump1090-mutability again.

I was able to pull this log up on my setup. I am not a 100% sure if this looks good or not. Any help would be helpfully. As I am still learning more about this stuff everyday. I am using the Flight Aware antenna and a Netbook computer, running Xubuntu on it. Many Thanks for the help.

8640659456 samples processed
0 samples dropped
0 Mode A/C messages received
14475760 Mode-S message preambles received
5940776 with bad message format or invalid CRC
4580375 with unrecognized ICAO address
3711153 accepted with correct CRC
243456 accepted with 1-bit error repaired
-19.9 dBFS mean signal power
-2.3 dBFS peak signal power
71 messages with signal power above -3dBFS
Messages from network clients:
0 Mode A/C messages received
85080 Mode S messages received
0 with bad message format or invalid CRC
0 with unrecognized ICAO address
85080 accepted with correct CRC
0 accepted with 1-bit error repaired
4039689 total usable messages
3 surface position messages received
169086 airborne position messages received
160087 global CPR attempts with valid positions
0 global CPR attempts with bad data
0 global CPR attempts that failed the range check
0 global CPR attempts that failed the speed check
210 global CPR attempts with insufficient data
8233 local CPR attempts with valid positions
8095 aircraft-relative positions
138 receiver-relative positions
769 local CPR attempts that did not produce useful positions
754 local CPR attempts that failed the range check
12 local CPR attempts that failed the speed check
0 CPR messages that look like transponder failures filtered
478216 non-ES altitude messages from ES-equipped aircraft ignored
509 unique aircraft tracks
31 aircraft tracks where only one message was seen
155 HTTP requests
CPU load: 13.9%
352579 ms for demodulation
109192 ms for reading from USB
38635 ms for network input and background tasks