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Thread: Very Dim Newbie v What Am I Seeing

  1. #21
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    Hi abcd567,

    Yes, even down here in Western Australia we have mobiles and, despite our beloved Telstra, a decent signal most of the time

    I was under the impression that filters were often used to more advantage in cities etc, where there is likely to be more stray noise around the receiving antenna. Where there is less noise then the filter may be filtering out signals that might be weak but usable. Of course, it is far more likely that I've mis-read something and that I could be talking out of my behind.

    I am pleased to say, however, that I am up and running again and managed to avoid falling from the ladder in order to put the antenna back in place

    Is there any advantage in changing the baud rate from 'default' to anything else with a Flight Aware Pro dongle? I have tried to Google the answer instead of relying on the patience of forum members but I couldn't glean any information from the WWW. My message rate shows about 18/sec received and 51/sec Positions/s (on my fancy graphs). I have no idea if this is normal and/or whether it is just a function of there being very little traffic around at the moment. Max range is 169nm today so far.

    As you may have gathered, none of this is vital because I'm just very pleased with the fact that it all works and I can see things. I'm just tinkering to see if I can do anything to better my set up.

  2. #22
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    Tweaking the Gain of dongle often improves. By default, dump1090 sets it to "max" which is 49.6 dB. Reduce it in steps of say about 3 dB i.e. 45, 42, 38, 35 etc. After every step watch performance for a while.

    It is also worth to conduct a scan to determine what signals you have in the area.


    Do I need a Filter? - Find RF Signals In Area

  3. #23
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    I'll have a play and see if I can see any discernible difference in performance by tweaking the gain. Presumably that is done in the settings page by writing "--Gain -3" in the 'Process Arguments' box.

    I attempted to conduct a scan of the area. Unfortunately, when I try to get the heat map (sudo wget https://raw.github etc) I get an "ERROR 400: Bad Request" message. The RTL-SDR and Python things loaded just fine.

    I copied and pasted the line so that I didn't make a mistake

    Edited to add: I've tried to do a bit of my own research. I think the sudo wget code tells the Pi to download the program at the GitHub address. I went into GitHub and looked for the program but got this response:

    We couldn’t find any repositories matching 'ke...map/heatmap.py'
    Perhaps it is no longer available and I should download a different heatmap.

    Edit to the edit: I've also just tried to use the Gain Optimization program but this time when I ran it a got the message:

    pi@raspberrypi:~ $ sudo ./optimize-gain-mut.py
    test 1 of 5
    [....] Restarting dump1090-mutability (via systemctl): dump1090-mutability.servi[ .k
    Traceback (most recent call last):
    File "./optimize-gain-mut.py", line 26, in <module>
    s.connect(('localhost',30003))
    File "/usr/lib/python2.7/socket.py", line 228, in meth
    return getattr(self._sock,name)(*args)
    socket.error: [Errno 111] Connection refused
    My sockets have an error apparently :-)
    Last edited by PaulSS; 2019-06-10 at 05:26.

  4. #24
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    You can use the graphs to check for the "red signals" which are >-3dB.

    If the percentage is larger than 1-5% you can think of reducing the gain.
    I've written down some rough guidelines here: https://discussions.flightaware.com/...g-gain/44482/2

    I'm not a fan of the gain optimization scripts, they don't necessarily give you proper results.
    You also have to stop fr24feed in your case to use them, because the dongle can't be used by two applications at the same time.

    One good thing about a co-linear antenna is that it does frequency filtering essentially.
    So that hopefully avoids overloading the LNA with noise.
    After the LNA is a SAW filter so that should help keep the noise out of the actual receiver.

    The rtl-sdr LNA has a two stage amplifier and better filtering. (The LNA is much much more resistent against overloading with non-ADS-B signals)
    You can also place it near the antenna to avoid cable loss, which can be a very significant factor regarding range.

    You might also want to check your terrain and how your "view" is: https://forum.flightradar24.com/thre...ange-I-can-Get

  5. #25
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    We couldn’t find any repositories matching 'ke...map/heatmap.py'

    Links that are long Have ... truncation. You need to copy the FULL contained path/link address it links to using right click, not the 'preview' text that has been shortened
    Just like the others in these posts
    Posts not to be taken as official support representation - Just a helpful uploader who tinkers

  6. #26
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    Thanks again, guys, for the continued information stream

    Wiedehopf, I ran the code to look at the maximum gain and came out with a result of 2.123. So I think I should probably just leave things alone. I have attached my ADSB signal report for the last 6 hours and I don't seem to wander beyond the red line very much.

    Also, I have attached the report of the terrain near me. I assume the red stuff is saying I won't see very much there. I find that a bot strange as my antenna is about 107' above sea level and west of us is an estuary, some low lying sand dunes and then the Indian Ocean. SO I would expect visibility to the moon and back, so don't really know why I've got red over the water.

    As I said before, I'm just tinkering and fully expect to be told not to touch anything as it all seems to be doing the best it can.

    Oblivian, thank you for the advice regarding truncation of long addresses. I will try the whole thing again but click on the link to get the full address. Lucky one of us knows what he's doing

    Note to my stupid self: read ALL the instructions. Yes, I can see all the way to the moon and back. Edited to add a picture of what happens when you do as you're told and zoom out
    Attached Images Attached Images
    Last edited by PaulSS; 2019-06-10 at 07:20.

  7. #27
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    URL shortening in a marked up code block? -.-

    I think putting the URL in quotes helps and the shell won't care about the quotes.

    Code:
    sudo apt-get install rtl-sdr
    sudo apt-get install python-imaging
    sudo wget "https://raw.githubusercontent.com/keenerd/rtl-sdr-misc/master/heatmap/heatmap.py"
    sudo chmod +x heatmap.py
    abcd567: Would probably make sense to modify your how-to to include the quotes to avoid automatic shortening.

  8. #28
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    Quote Originally Posted by PaulSS View Post
    Wiedehopf, I ran the code to look at the maximum gain and came out with a result of 2.123. So I think I should probably just leave things alone. I have attached my ADSB signal report for the last 6 hours and I don't seem to wander beyond the red line very much.
    That percentage should also be shown in the first graph at the bottom. (Messages >-3dB)

    The mean level shouldn't be allowed much over -10 dB in my experience, -8 dB might be ok.
    But the percentage of messages >-3dB is a better way to determine gain.

    Also, I have attached the report of the terrain near me. I assume the red stuff is saying I won't see very much there. I find that a bot strange as my antenna is about 107' above sea level and west of us is an estuary, some low lying sand dunes and then the Indian Ocean. SO I would expect visibility to the moon and back, so don't really know why I've got red over the water.
    In the top right of the map you need to click "up in the air" to change the mode.
    It will then draw outlines for your theoretical range for planes at 10000 and 30000 ft.

    You need to zoom out with the - button on the bottom left to see it though.

    The red stuff is "visibility cloak" which is something quite different.

    Looks like you can see around 200 nmi, but i suspect that is for 30000 ft, it makes sense to check for 40000 ft
    Last edited by wiedehopf; 2019-06-10 at 07:30.

  9. #29
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    Yes, I put 37000 as that is what I would expect the EK flight from DXB to PER to be flying at and got 263nm. SO my antenna getting 208nm isn't too bad I thought

    I did try to persist with the heat map of stray RF in my area but ran up against another error code, about which I have no idea. Instead of Tuner Gain settings and Exact Sample rates I got a USB interface error:

    sudo rtl_power -f 800M:1200M:100k -i 30 -c 50% -e 30m -g 30 -F 9 >scan.csv
    Number of frequency hops: 286
    Dongle bandwidth: 2797202Hz
    Downsampling by: 1x
    Cropping by: 50.00%
    Total FFT bins: 9152
    Logged FFT bins: 4576
    FFT bin size: 87412.56Hz
    Buffer size: 16384 bytes (2.93ms)
    Reporting every 30 seconds
    Found 1 device(s):
    0: Realtek, RTL2832U, SN: 00001000

    Using device 0: Generic RTL2832U
    usb_claim_interface error -6
    Failed to open rtlsdr device #0.
    Again, not a snag, just playing

  10. #30
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    Quote Originally Posted by wiedehopf View Post
    URL shortening in a marked up code block? -.-

    I think putting the URL in quotes helps and the shell won't care about the quotes.

    Code:
    sudo apt-get install rtl-sdr
    sudo apt-get install python-imaging
    sudo wget "https://raw.githubusercontent.com/keenerd/rtl-sdr-misc/master/heatmap/heatmap.py"
    sudo chmod +x heatmap.py
    abcd567: Would probably make sense to modify your how-to to include the quotes to avoid automatic shortening.
    Possibly wasn't, made assumption based on error result containing them
    Posts not to be taken as official support representation - Just a helpful uploader who tinkers

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