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Thread: I'm trying to understand which options it's better ? Automatic Gain Control (-10)

  1. #1
    Flight attendant
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    May 2014
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    I'm trying to understand which options it's better ? Automatic Gain Control (-10)

    or max Gain (+49.6) ?
    that is the result i'm getting on my graph.

    001c.jpg
    002c.jpg
    003c.jpg
    Last edited by ramimz; 2019-06-15 at 07:49.

  2. #2
    Captain
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    you excluded the most relevant graph: the first one, message rate.

    Both settings are probably fine.

    If you like looking at local close by low flying traffic, then 49.6 is most likely the better setting for you.
    With the higher gain some low flying close by traffic will disappear from the map.

    (maybe at 3 miles from your antenna)

  3. #3
    Flight attendant
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    Hi..... sorry about that.
    here is the one with message rate.

    004c.jpg
    Attached Images Attached Images
    Last edited by ramimz; 2019-06-15 at 07:42.

  4. #4
    Captain
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    Compare two week days, that's a bit better than comparing like this.

    Also the graphs are an old version and don't display message >-3dB correctly.
    And you switched up the labels for -10 and 49.6 it seems.

    It's best to compare two complete weeks.

    Anyway these are my thoughts on gain:
    https://github.com/wiedehopf/adsb-wi...ptimizing-gain
    Last edited by wiedehopf; 2019-06-14 at 17:25.

  5. #5
    Captain abcd567's Avatar
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    First of all for ADS-B signals, the "gain -10" or "gain agc" does not set the gain to AGC. It sets gain to about 55 dB, which is higher than maximum value (49.6 dB) which can be set manually. This is due to very fluctuating nature of ADSB signal, while dongle is actually designed for receiving TV stations which have a stable signal level. In addition it is also due to a quirk in the RTL dongles.

    The value "gain max" sets gain to max designated value of 49.6

    Now the important question: What value is better?
    This depends entirely on location, hardware, and strength of interfering Cell/Mobile signals. It also depends on if you prefer to see long distance planes (highest gain setting) or close by / overhead planes (very low gain setting).

    For further reading:

    (1) Dump1090-mutability: About gain -10

    (2) ABOUT AGC

    (3) Do I need a Filter? - Find RF Signals In Area
    Last edited by abcd567; 2019-06-14 at 18:15.

  6. #6
    Flight attendant
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    Quote Originally Posted by wiedehopf View Post
    And you switched up the labels for -10 and 49.6 it seems.

    It's best to compare two complete weeks.

    Anyway these are my thoughts on gain:
    https://github.com/wiedehopf/adsb-wi...ptimizing-gain
    I fix it

    i will try it for longest time...... thanks

  7. #7
    Flight attendant
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    Quote Originally Posted by abcd567 View Post
    First of all for ADS-B signals, the "gain -10" or "gain agc" does not set the gain to AGC. It sets gain to about 55 dB, which is higher than maximum value (49.6 dB) which can be set manually. This is due to very fluctuating nature of ADSB signal, while dongle is actually designed for receiving TV stations which have a stable signal level. In addition it is also due to a quirk in the RTL dongles.

    The value "gain max" sets gain to max designated value of 49.6

    Now the important question: What value is better?
    This depends entirely on location, hardware, and strength of interfering Cell/Mobile signals. It also depends on if you prefer to see long distance planes (highest gain setting) or close by / overhead planes (very low gain setting).
    Thank you very much..... i have a lot of info to read on this weekend

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