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 Post subject: Gain Adjustment...
PostPosted: Tue Apr 26, 2016 12:27 am 
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dstreufe - FlightAware user avatar

Joined: Sun Sep 18, 2005 11:00 pm
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So what is the best way to test various gain levels on the pro-stick without having to wait 24 hours for stats on the dashboard to populate? Is the best way to just look at your local dump1090 web interface and eyeball it?


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 Post subject: Re: Gain Adjustment...
PostPosted: Tue Apr 26, 2016 2:44 am 
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tottoman - FlightAware user avatar

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I really hope someone with the knowledge does a comprehensive write up on this matter. I guess we are quite few out there with the same issue regarding the gain adjustments.

What i really would like to see is a guide how to interpret the charts from dump1090 mutability, and what levels one should try to reach.


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 Post subject: Re: Gain Adjustment...
PostPosted: Tue Apr 26, 2016 9:37 am 
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It is not easy. Each setup is different.
Someone could write a program to run for a few hours to work it out.

I have had good results running at 30/35 and max. I get a much lower noise floor at the 30/35 settings.
I am still experimenting. One change at a time.

Having collectd graphs from Joe's scripts makes things a little easier. I am able to look back hours, days, weeks. I just need to note when I changed the settings.
ads-b-flight-tracking-f21/ads-b-receiver-project-setup-scripts-t36532.html


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 Post subject: Re: Gain Adjustment...
PostPosted: Tue Apr 26, 2016 9:43 am 
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dstreufe - FlightAware user avatar

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If the gain is set to "0" does that effectively turn off the amp and it becomes basically a standard SDR dongle?


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 Post subject: Re: Gain Adjustment...
PostPosted: Tue Apr 26, 2016 10:22 am 
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cptdevine - FlightAware user avatar

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jonhawkes2030 wrote:
It is not easy. Each setup is different.
Someone could write a program to run for a few hours to work it out.

I have had good results running at 30/35 and max. I get a much lower noise floor at the 30/35 settings.
I am still experimenting. One change at a time.

Having collectd graphs from Joe's scripts makes things a little easier. I am able to look back hours, days, weeks. I just need to note when I changed the settings.
ads-b-flight-tracking-f21/ads-b-receiver-project-setup-scripts-t36532.html



I've been wanting to setup a script to change the gain setting once every hour to test each setting and find the best results.

Unfortunately, that is a bit beyond what I know how to do. :lol:

Next week I'll have some time to figure out how to setup a cron job and a script to do this.


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 Post subject: Re: Gain Adjustment...
PostPosted: Tue Apr 26, 2016 10:38 am 
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dstreufe wrote:
If the gain is set to "0" does that effectively turn off the amp and it becomes basically a standard SDR dongle?


No - the gain adjustment is not changing the amplification of the extra LNA installed on the ProStick - same as with the standard dongles, it's changing the gain of the amp that's part of the tuner.

The additional LNA featured in the pro-stick has a fixed gain value.

The core concept behind the ProStick is the inclusion of the fixed-gain, higher quality, lower noise LNA should allow you to use a lower tuner gain setting - since the amp in the tuner introduces far more noise.


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 Post subject: Re: Gain Adjustment...
PostPosted: Tue Apr 26, 2016 11:03 am 
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BartJr - FlightAware user avatar

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Location: Austin, TX
cptdevine wrote:
I've been wanting to setup a script to change the gain setting once every hour to test each setting and find the best results.


I wrote a script to sort of do this. I only ran for 15 second intervals because the amount of traffic can change a lot throughout the day. But you can try different durations.

It gives an output like:

Code:
test 1 of 10
gain= 49.6 messages= 771 positions= 41 planes= 49
gain= 48.0 messages= 742 positions= 43 planes= 51
gain= 44.5 messages= 785 positions= 37 planes= 51
gain= 40.2 messages= 677 positions= 35 planes= 51
gain= 37.2 messages= 743 positions= 32 planes= 48
gain= 32.8 messages= 711 positions= 37 planes= 46
test 2 of 10
gain= 49.6 messages= 667 positions= 32 planes= 44
...
test 10 of 10
gain= 49.6 messages= 757 positions= 43 planes= 49
gain= 48.0 messages= 814 positions= 37 planes= 51
gain= 44.5 messages= 830 positions= 37 planes= 50
gain= 40.2 messages= 766 positions= 49 planes= 43
gain= 37.2 messages= 671 positions= 31 planes= 50
gain= 32.8 messages= 651 positions= 27 planes= 43

===Totals===
Gain, Messages, Positions, Aircraft
49.6 6925 361 73
48.0 7230 331 76
44.5 7149 347 75
40.2 6883 352 71
37.2 7071 351 69
32.8 6653 332 69


Plotting the data into excel you can give helpful graphs
Image

Although for tuning the Prostick it didn't help me that much, since a lot of gains gave similar results :?:
Image

Here's the code. It's pretty dumb (like it just waits 2 seconds after starting dump1090 rather than checking to see if dump1090 is actually ready). You probably want to change the measure_duration, ntests, and gains variables at the top.

Stop any existing dump1090 process before running the script. sudo /etc/init.d/fadump1090.sh stop or sudo service dump1090-mutability stop


Code:
#!/usr/bin/python2
import time, socket, subprocess

measure_duration = 15 #seconds
ntests = 10  #Number of tests
mutability = False    #set to True if you use dump1090-mutability
#gains = "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".split()
gains = "36.4 38.6 40.2 42.1 44.5 48.0 49.6".split()
#gains = "22.9 25.4 28.0 29.7 32.8 33.8 36.4".split()
gains.reverse()
results = {}

for i in range(ntests):
  print "test", i+1, "of", ntests
  for g in gains:
   if g not in results:
      results[g] = [0,0,{}] #msgs, positions, aircraft
   if mutability:
       p = subprocess.Popen(('/usr/bin/dump1090-mutability --net --gain '+g+' --oversample --fix --phase-enhance --quiet').split(),shell=False,stdout=subprocess.PIPE, stderr=subprocess.PIPE)
   else:
       p = subprocess.Popen(('/usr/bin/dump1090 --net --gain '+g+' --quiet').split(),shell=False,stdout=subprocess.PIPE, stderr=subprocess.PIPE)
   time.sleep(2)
   s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
   s.connect(('localhost',30003))
   t = time.time()
   d = ''
   while 1:
      d += s.recv(32)
      if time.time() - t > measure_duration:
         break
   s.close()
   p.terminate()
   messages = 0
   positions = 0
   planes = {}
   for l in d.split('\n'):
      a = l.split(',')
      messages += 1
      if len(a) > 4:
         if a[1] == '3':
            positions += 1
         planes[a[4]] = 1
   print "gain=",g, "messages=", messages, "positions=", positions, "planes=", len(planes.keys())
   results[g][0] += messages
   results[g][1] += positions
   for hex in planes.keys():
      results[g][2][hex] = 1

print "\n===Totals==="
print "Gain, Messages, Positions, Aircraft"
for g in gains:
   (messages,positions,planes) = results[g]
   print g, messages, positions, len(planes.keys())



Last edited by BartJr on Fri Jul 15, 2016 9:53 pm, edited 2 times in total.

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 Post subject: Re: Gain Adjustment...
PostPosted: Tue Apr 26, 2016 11:07 am 
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dstreufe - FlightAware user avatar

Joined: Sun Sep 18, 2005 11:00 pm
Posts: 195
JonHanford wrote:
dstreufe wrote:
If the gain is set to "0" does that effectively turn off the amp and it becomes basically a standard SDR dongle?


No - the gain adjustment is not changing the amplification of the extra LNA installed on the ProStick - same as with the standard dongles, it's changing the gain of the amp that's part of the tuner.

The additional LNA featured in the pro-stick has a fixed gain value.

The core concept behind the ProStick is the inclusion of the fixed-gain, higher quality, lower noise LNA should allow you to use a lower tuner gain setting - since the amp in the tuner introduces far more noise.


So, really, the object is to run the gain as low as possible as long as you can still get traffic at your "maximum" range..? Is the advice to run "max gain" if you're using a filter necessarily accurate then?


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 Post subject: Re: Gain Adjustment...
PostPosted: Tue Apr 26, 2016 1:27 pm 
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lignumaqua - FlightAware user avatar

Joined: Fri Oct 16, 2015 12:05 am
Posts: 125
Location: Austin, TX
@BartJr

That's a very interesting idea, thanks for providing the Python script. Just ran it against a ProStick with a full range of allowed gain values and the same 15 second interval. Just as you found, the results are highly inconclusive! :lol:

Code:
===Totals===
Gain, Messages, Positions, Aircraft
49.6 46301 2842 194
48.0 45442 2840 194
44.5 46277 2895 189
43.9 46921 2922 198
43.4 47035 2894 191
42.1 45787 2875 192
40.2 46333 2868 196
38.6 47250 2914 195
37.2 47150 2846 198
36.4 47876 2941 195
33.8 47486 2926 194
32.8 47854 2972 192
29.7 47968 3064 200
28.0 48427 2976 199
25.4 48744 3008 201
22.9 47377 2894 202
20.7 48416 2901 201


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 Post subject: Re: Gain Adjustment...
PostPosted: Tue Apr 26, 2016 2:31 pm 
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Me109 - FlightAware user avatar

Joined: Sun Jan 01, 2006 9:00 pm
Posts: 48
FWIW, I normalize the raw values into ADSB messages per ADSB aircraft (excluding MLAT). There's too much variability IMO to look at time slices of message and aircraft quantities. I also run for at least 24 hours to collect enough data points and compare the percent change delta to the previous day, then choose a neighboring site to see how much that site changed and whether I'm +/-. I only tune in real time for gross gain adjustments.

That's how I do it anyway...with a SQL database to store the values over a longer period than available on the FA stats page.


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 Post subject: Re: Gain Adjustment...
PostPosted: Tue Apr 26, 2016 2:37 pm 
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BartJr - FlightAware user avatar

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@lignumaqua I lifted the idea from obj who proposed it as a dump1090-mut enhancement :)


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 Post subject: Re: Gain Adjustment...
PostPosted: Wed Apr 27, 2016 6:00 pm 
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Joined: Wed Sep 09, 2015 5:23 pm
Posts: 11
BartJr wrote:
cptdevine wrote:
I've been wanting to setup a script to change the gain setting once every hour to test each setting and find the best results.


I wrote a script to sort of do this. I only ran for 15 second intervals because the amount of traffic can change a lot throughout the day. But you can try different durations.

It gives an output like:



[/code]


Thanks for posting the script.

I also have had mixed results trying to dial in gain, I think the issue is the variation of traffic during the sample times.


Just had an idea. What if you set this up so that you ran two dongles, both fed from the same antenna via a splitter? Use one dongle as the reference and the other as the variable to test gain?


You would lose sensitivity with the splitter, but it would only be used for calibration.

Make sense?


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 Post subject: Re: Gain Adjustment...
PostPosted: Wed Apr 27, 2016 6:24 pm 
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tjowen - FlightAware user avatar

Joined: Mon Mar 09, 2015 11:17 am
Posts: 378
cptdevine wrote:
BartJr wrote:
cptdevine wrote:
I've been wanting to setup a script to change the gain setting once every hour to test each setting and find the best results.


I wrote a script to sort of do this. I only ran for 15 second intervals because the amount of traffic can change a lot throughout the day. But you can try different durations.

It gives an output like:



[/code]


Thanks for posting the script.

I also have had mixed results trying to dial in gain, I think the issue is the variation of traffic during the sample times.


Just had an idea. What if you set this up so that you ran two dongles, both fed from the same antenna via a splitter? Use one dongle as the reference and the other as the variable to test gain?


You would lose sensitivity with the splitter, but it would only be used for calibration.

Make sense?


The splitter idea is good but you could also use the data from a second system as a reference. The data rate changes from traffic changes would be evident on a second nearby system. Perhaps even a friends system in the same general area.


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 Post subject: Re: Gain Adjustment...
PostPosted: Wed Apr 27, 2016 7:00 pm 
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paulviola - FlightAware user avatar

Joined: Sat Feb 21, 2009 4:00 pm
Posts: 9
cptdevine wrote:
BartJr wrote:
cptdevine wrote:
I've been wanting to setup a script to change the gain setting once every hour to test each setting and find the best results.


I wrote a script to sort of do this. I only ran for 15 second intervals because the amount of traffic can change a lot throughout the day. But you can try different durations.

It gives an output like:



[/code]


Thanks for posting the script.

I also have had mixed results trying to dial in gain, I think the issue is the variation of traffic during the sample times.


Just had an idea. What if you set this up so that you ran two dongles, both fed from the same antenna via a splitter? Use one dongle as the reference and the other as the variable to test gain?


You would lose sensitivity with the splitter, but it would only be used for calibration.

Make sense?


This is my current strategy.

My setup is Cantenna -> Inline Amp -> DC Power -> Splitter ->
1) Raspberry Pi B+, Regular tuner / Gain 42
2) Raspberry Pi 3, Pro Tuner, FA Filter / Gain 16.6
(Note: My cantenna is on my second story roof and followed by about 40 feet of coax)

I came to these gain numbers mostly by trial and error with my baseline receiver being the B+. I then compared results between the two to get the gain to where it is on the Pi 3. The Pi 3 does slightly better, most likely due to the filter.

I have graphs setup on the Pi 3 as it is a fresh install using Dump1090-Muta/PiAware add-on and the B+ is a vanilla PiAware image.

I would be interested in some more in depth tuning information as most of my results are pure speculation...

Here is my signal to noise graph from the Pi 3
Image
Image

My Sites are http://flightaware.com/adsb/stats/user/paulviola


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 Post subject: Re: Gain Adjustment...
PostPosted: Thu Apr 28, 2016 5:54 pm 
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lignumaqua - FlightAware user avatar

Joined: Fri Oct 16, 2015 12:05 am
Posts: 125
Location: Austin, TX
Realized I was being dumb when running the above Python script. I hadn’t killed my usual dump1090 instance so all I was doing was reading the same values again and again!

I modified the script to allow simultaneous testing with normal dump1090 operation and got somewhat more likely results where the figures drop off at lower gain values once you get below a threshold. I'm going to run it again over a 24 hour period (about 250 iterations rather than 10) and see how that looks.

Code:
===Totals===
Gain, Messages, Positions, Aircraft
49.6 45072 3316 225
48.0 45127 3421 230
44.5 45589 3365 226
43.9 45624 3282 223
43.4 45022 3232 220
42.1 45046 3337 217
40.2 44289 3227 221
38.6 43904 3134 222
37.2 43799 3180 220
36.4 42600 3076 215
33.8 42577 3098 213
32.8 43107 3167 212
29.7 40988 2990 202
28.0 38121 2789 200
25.4 32601 2392 179
22.9 31111 2284 175
20.7 25329 1897 155


Last edited by lignumaqua on Thu Apr 28, 2016 6:32 pm, edited 1 time in total.

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 Post subject: Re: Gain Adjustment...
PostPosted: Thu Apr 28, 2016 6:21 pm 
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dstreufe - FlightAware user avatar

Joined: Sun Sep 18, 2005 11:00 pm
Posts: 195
Are those the only valid values for gains? What happens if you just use integers?


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 Post subject: Re: Gain Adjustment...
PostPosted: Thu Apr 28, 2016 6:26 pm 
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lignumaqua - FlightAware user avatar

Joined: Fri Oct 16, 2015 12:05 am
Posts: 125
Location: Austin, TX
dstreufe wrote:
Are those the only valid values for gains? What happens if you just use integers?

dump1090 rounds to the nearest one from the full list:

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


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 Post subject: Re: Gain Adjustment...
PostPosted: Thu Apr 28, 2016 7:52 pm 
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crkbday - FlightAware user avatar

Joined: Tue Apr 21, 2015 7:57 pm
Posts: 92
lignumaqua wrote:
Code:
===Totals===
Gain, Messages, Positions, Aircraft
49.6 45072 3316 225
48.0 45127 3421 230
44.5 45589 3365 226
43.9 45624 3282 223
43.4 45022 3232 220
42.1 45046 3337 217
40.2 44289 3227 221
38.6 43904 3134 222
37.2 43799 3180 220
36.4 42600 3076 215
33.8 42577 3098 213
32.8 43107 3167 212
29.7 40988 2990 202
28.0 38121 2789 200
25.4 32601 2392 179
22.9 31111 2284 175
20.7 25329 1897 155

This illustrates an interesting phenomenon. The maxima for messages and the maxima for aircraft do not necessarily occur at the same gain. I've personally noticed that I can increase a/c count with more gain but at the expense of message count.


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 Post subject: Re: Gain Adjustment...
PostPosted: Thu Apr 28, 2016 7:55 pm 
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crkbday - FlightAware user avatar

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lignumaqua wrote:
I modified the script to allow simultaneous testing with normal dump1090 operation...

BTW, care to share the modified script? :D


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 Post subject: Re: Gain Adjustment...
PostPosted: Thu Apr 28, 2016 9:28 pm 
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lignumaqua - FlightAware user avatar

Joined: Fri Oct 16, 2015 12:05 am
Posts: 125
Location: Austin, TX
crkbday wrote:
lignumaqua wrote:
I modified the script to allow simultaneous testing with normal dump1090 operation...

BTW, care to share the modified script? :D

Happy to do so, but be warned, this *will* mess up your local collectd stats. Depending on the timing between when collectd samples and the gain levels switching you'll likely see some strange results. However, the overall average won’t change much and you'll keep feeding data to FA. The constant rebooting of dump1090 will also break MLAT for the duration of the test. It's a fairly crude hack of BartJr's code that rewrites the dump1090-mutability config file with a different gain and then restarts dump1090. Please don’t use this unless you are prepared to deal with all that. No warranty is implied or should be inferred, if it breaks you get to keep both pieces! :shock:

PS - If someone knows a cleaner way of restarting dump1090 with a different gain, then please post it.

Code:
#!/usr/bin/python2
import time, socket, subprocess, fileinput, os

measure_duration = 62 #seconds
ntests = 10
gains = "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".split()
#gains = "36.4 38.6 40.2 42.1 44.5 48.0 49.6".split()
#gains = "22.9 25.4 28.0 29.7 32.8 33.8 36.4".split()
gains.reverse()
results = {}

for i in range(ntests):
  print "test", i+1, "of", ntests
  for g in gains:
   if g not in results:
      results[g] = [0,0,{}] #msgs, positions, aircraft

   for line in fileinput.input('/etc/default/dump1090-mutability', inplace=1):
      if line.startswith('GAIN'):
         print 'GAIN='+g
      else:
         print line,
   os.system("sudo /etc/init.d/dump1090-mutability restart")
   time.sleep(2)
   s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
   s.connect(('localhost',30003))
   t = time.time()
   d = ''
   while 1:
      d += s.recv(32)
      if time.time() - t > measure_duration:
         break
   s.close()
   messages = 0
   positions = 0
   planes = {}
   for l in d.split('\n'):
      a = l.split(',')
      messages += 1
      if len(a) > 4:
         if a[1] == '3':
            positions += 1
         planes[a[4]] = 1
   print "gain=",g, "messages=", messages, "positions=", positions, "planes=", len(planes.keys())
   results[g][0] += messages
   results[g][1] += positions
   for hex in planes.keys():
      results[g][2][hex] = 1

print "\n===Totals==="
print "Gain, Messages, Positions, Aircraft"
for g in gains:
   (messages,positions,planes) = results[g]
   print g, messages, positions, len(planes.keys())


Last edited by lignumaqua on Fri Apr 29, 2016 2:26 pm, edited 1 time in total.

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 Post subject: Re: Gain Adjustment...
PostPosted: Thu Apr 28, 2016 11:34 pm 
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paulviola - FlightAware user avatar

Joined: Sat Feb 21, 2009 4:00 pm
Posts: 9
From my Pi 3

Edit: This was done with 10 second intervals for a total cycle of about 5 minutes each. I figure this gets a close snapshot of the sky rather than planes coming and going with 60 second intervals.

Code:
===Totals===
Gain, Messages, Positions, Aircraft
49.6 2793 369 22
48.0 2639 354 22
44.5 2740 348 24
43.9 2743 354 25
43.4 2674 351 23
42.1 2672 349 25
40.2 2804 373 24
38.6 2817 382 26
37.2 2821 386 25
36.4 2891 376 26
33.8 2927 398 27
32.8 2981 396 26
29.7 2872 366 26
28.0 2704 348 26
25.4 2629 343 25
22.9 2609 340 25
20.7 2582 326 25
19.7 2614 345 25
16.6 2423 310 27
15.7 2373 297 24
14.4 2201 292 24
12.5 2019 279 22
8.7 1928 274 21
7.7 1943 279 20
3.7 1909 263 20
2.7 1731 243 20
1.4 1431 194 19
0.9 1344 188 19
0.0 936 127 15


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 Post subject: Re: Gain Adjustment...
PostPosted: Fri Apr 29, 2016 10:15 am 
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caius - FlightAware user avatar

Joined: Sat Mar 07, 2015 4:51 pm
Posts: 249
lignumaqua wrote:
Happy to do so, but be warned, this *will* mess up your local collectd stats. Depending on the timing between when collectd samples and the gain levels switching you'll likely see some strange results. However, the overall average won’t change much and you'll keep feeding data to FA. The constant rebooting of dump1090 will also break MLAT for the duration of the test. It's a fairly crude hack of BartJr's code that rewrites the dump1090-mutability config file with a different gain and then restarts dump1090. Please don’t use this unless you are prepared to deal with all that. No warranty is implied or should be inferred, if it breaks you get to keep both pieces! :shock:

PS - If someone knows a cleaner way of restarting dump1090 with a different gain, then please post it.


I got this error:

Code:
Traceback (most recent call last):
  File "./gain2.py", line 23, in <module>
    os.system("sudo /etc/init.d/dump1090-mutability restart")
NameError: name 'os' is not defined


Adding 'os' to the list of imported modules fixed it.


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 Post subject: Re: Gain Adjustment...
PostPosted: Fri Apr 29, 2016 1:30 pm 
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tottoman - FlightAware user avatar

Joined: Thu Apr 07, 2016 4:36 am
Posts: 60
Location: Sweden
Pls explain for a noob, how do i run this script, and find the logfile? :)


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 Post subject: Re: Gain Adjustment...
PostPosted: Fri Apr 29, 2016 2:27 pm 
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lignumaqua - FlightAware user avatar

Joined: Fri Oct 16, 2015 12:05 am
Posts: 125
Location: Austin, TX
caius wrote:
Adding 'os' to the list of imported modules fixed it.

Yes, sorry, I had that of course, but missed it out in the version I copied/pasted. :roll: I've added it to the code above.


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 Post subject: Re: Gain Adjustment...
PostPosted: Fri Apr 29, 2016 6:07 pm 
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lignumaqua - FlightAware user avatar

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Location: Austin, TX
This is after running the test script on my system (FlightAware antenna in the roof space with about 20ft of RG6 to a FA Filter and ProStick in a Pi2) for 24 hours. (It clobbered my stats for the day as expected, but kept feeding data)

This was 70 iterations of the test, running 62 seconds each per gain setting.

Code:
===Totals===
Gain, Messages, Positions, Aircraft
20.7 498628 34177 1148
22.9 625771 42228 1291
25.4 678968 44266 1358
28.0 792787 52516 1451
29.7 836895 56191 1481
32.8 887074 59649 1499
33.8 911740 60627 1540
36.4 929263 62254 1542
37.2 937247 62541 1548
38.6 943844 62937 1569
40.2 958554 64469 1555
42.1 963873 64462 1545
43.4 981767 65265 1559
43.9 981427 65904 1561
44.5 985292 66594 1581
48.0 989690 66515 1573
49.6 997097 67386 1571


Messages and Positions peak at the highest gain. Aircraft peak at 44.5 dB. However, realistically, there is very little change in anything once above 33 dB.

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