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how deep are the loop minima

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  • Vojtech
    Hello. I measured the maximum and minimum band noise of my 1ft dmr loop standing on a window sill. I am living near a HV power line and the attenuation of the
    Message 1 of 4 , Feb 10, 2013
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      Hello.

      I measured the maximum and minimum band noise of my 1ft dmr loop standing on a window sill. I am living near a HV power line and the attenuation of the powerline noise when turned towards the noise source is in the ballpark of -10dB (-13dB if I am optimistic). Is this a usual value, or shall I strive to do better?

      Thanks, Vojtech OK1IAK
    • Andrew Ikin
      Vojtech wrote Feb 10. I measured the maximum and minimum band noise of my 1ft dmr loop standing on a window sill. I am living near a HV power line and the
      Message 2 of 4 , Feb 10, 2013
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        Vojtech wrote Feb 10.
         
         
        I measured the maximum and minimum band noise of my 1ft dmr loop standing on a window sill. I am living near a HV power line and the attenuation of the powerline noise when turned towards the noise source is in the ballpark of -10dB (-13dB if I am optimistic). Is this a usual value, or shall I strive to do better?

        Thanks, Vojtech OK1IAK
         
         
         
        Dear Vojtech,
         
        The null width of the loop is only a few degrees. Hence,  as the noise source of the power-line is much wider than the loops null apperture then, is will be impossible to achieve a high null. Therefore a -10dB null is about right. Other factors that can affect the null is a lack of loop balance or poor isolation of the antenna to mains borne noise.
         
        Kind regards
         
        Andrew Ikin


      • fernando talamantes
        Hi Vojtech: you must try at more distance from power lines. if u are living very close, you cant get a good null because the antenna is receiving noise
        Message 3 of 4 , Feb 10, 2013
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          Hi Vojtech: you must try at more distance from power lines. if u are living very close, you cant get a good null because the antenna is receiving noise transmited along the power line. the transmiter (power line) is not a puntual antenna and probably are receiving noise from angles different than the minimal rx .
          73
          Fernando XE2EJ

          --- On Sun, 2/10/13, Vojtech <bubnikv@...> wrote:

          From: Vojtech <bubnikv@...>
          Subject: [loopantennas] how deep are the loop minima
          To: loopantennas@yahoogroups.com
          Date: Sunday, February 10, 2013, 9:09 AM

           
          Hello.

          I measured the maximum and minimum band noise of my 1ft dmr loop standing on a window sill. I am living near a HV power line and the attenuation of the powerline noise when turned towards the noise source is in the ballpark of -10dB (-13dB if I am optimistic). Is this a usual value, or shall I strive to do better?

          Thanks, Vojtech OK1IAK

        • vbifyz
          You can also try and tilt the loop around the horizontal axis. This may give you few more dB. This is my actual observation. Note that the orientation that
          Message 4 of 4 , Feb 11, 2013
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            You can also try and tilt the loop around the horizontal axis. This may give you few more dB. This is my actual observation.
            Note that the orientation that gives maximum signal-to-noise is not necessary the same as the lowest noise, but it is usually pretty close.

            73, Mike

            --- In loopantennas@yahoogroups.com, fernando talamantes wrote:
            >
            > Hi Vojtech: you must try at more distance from power lines. if u are living very close, you cant get a good null because the antenna is receiving noise transmited along the power line. the transmiter (power line) is not a puntual antenna and probably are receiving noise from angles different than the minimal rx .
            > 73
            > Fernando XE2EJ
            >
            > --- On Sun, 2/10/13, Vojtech wrote:
            >
            >
            > From: Vojtech
            > Subject: [loopantennas] how deep are the loop minima
            > To: loopantennas@yahoogroups.com
            > Date: Sunday, February 10, 2013, 9:09 AM
            >
            >
            >
            >  
            >
            >
            >
            > Hello.
            >
            > I measured the maximum and minimum band noise of my 1ft dmr loop standing on a window sill. I am living near a HV power line and the attenuation of the powerline noise when turned towards the noise source is in the ballpark of -10dB (-13dB if I am optimistic). Is this a usual value, or shall I strive to do better?
            >
            > Thanks, Vojtech OK1IAK
            >
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