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RF Gain: More Powerful than NR?

Discussion in 'Amateur Radio News' started by KE0EYJ, Feb 11, 2017.

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  1. K3RW

    K3RW Ham Member QRZ Page

    You know, that is probably it. Our powerlines are all buried here and I'm right next to a corner lot on 3 sides due to the odd lot shapes behind me, and a culdesac behind. So I actually have 7 neighbors.

    That and the cannabis grow lights, that's definitely possible. Just need a card here in WA to grow-your-own. In OR, anyone can. Lots of High wattage grow light dealers around here.

    If that's the source, and I'd bet it probably is, not sure how to get around it.

    Maybe I can null it out with a box or software, maybe even a loop antenna. But for tx, I wonder if my signal is disturbed. I don't make nearly as many QSOs here that I did elsewhere. If I can hear them, they don't seem to hear me well. I figured my soon-to-be vertical might help, but with that level of ground noise, it could also be even worse!

    I'll start a new thread and post some screenshots of what I'm seeing. Thanks everyone!
     
  2. KM3F

    KM3F Ham Member QRZ Page

    Someone mentioned AF filtering awhile back.
    On my KW 2000, I use a number of helps when trying a difficult contact.
    The Beat Cancel on, then go to bandpass manual sweep control filter using the Function button.
    This depends on how you hear the best setting with head phones.
    Get help from the receive EQ and the DSP in combination.
    Then the two NR functions as needed.
    There is another help not in the radio.
    That is a short receiving antenna if the noise is a local area source and not coming in long distance with the desired signal.
    Signal levels drop but he noise drops faster on a short antenna.
    One may not believe it but I can switch receive to my Mosley 10/15/20m beam on 75m and drop a lot of noise out and hear the DX under very difficult conditions.
    Lots of ways to help but many don't take advantage of all the radios have to offer.
    Good luck.
     
    KE0EYJ likes this.
  3. K2EZ

    K2EZ Ham Member QRZ Page

    I adjust down the RF gain to better hear signals in the noise.

    It my non-technical understanding as to why this works is fairly simple.

    There is some noise present in any received signal, be that atmospheric noise or the noise figure of the early RF stages.

    When RF gain is high, short of overload of intended or adjacent signals, if the signal one is receiving is strong the RF gain setting isn't too critical as the signal is well out of the noise and AGC will cut back gain and push the noise floor down making listening cleaner.

    When signals are down at the noise level however, that noise competes with the intended signal with perhaps signal completely in the noise or just a little above. As the RF gain is reduced the noise will start to fall off the detection threshold providing a signal with less noise to the audio amplification stages.

    If the signal is in the noise, you can't just lower the gain to the point where all the noise falls off because the intended signal is lost, but even noise that may be lower than the intended signal will make copy more difficult so dropping that weaker noise out increase intelligibility. Thus a point can be reached of maximum intelligibility where dropping noise (and even some of the intended signal) off is balanced against the amount of intended signal that is kept.

    Don't know if that makes sense. It is how I perceive it as work and I agree it is a good technique to adjust down RF gain under such conditions.
     
    KE0EYJ likes this.
  4. KE0EYJ

    KE0EYJ Ham Member QRZ Page

    I have been experimenting with the notch filter, and it sometimes seem to cut a bit more hiss, if I have it set just right.
     

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