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Re: [WestMichiganHams] Elusive interference

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  • Andrew Young
    I am surprised the cable company hasn t been out to fix it. I had my CATV amp in the basement turned up too high and they came a-knocking. The tech showed me
    Message 1 of 7 , Aug 13, 2006
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      I am surprised the cable company hasn't been out to fix it.  I had my CATV amp in the basement turned up too high and they came a-knocking.  The tech showed me with his meter where the strongest signal came from.
       
      I was having mild 2 meter problems, but not as much as Mark.
       
      Andrew
       
      ----- Original Message -----
      From: k8mhz@...
      Sent: Saturday, August 12, 2006 2:14 PM
      Subject: Re: [WestMichiganHams] Elusive interference

      Good lead!!
       
      I found a CATV amp here that I have trouble with pegging my meter on 145.25.  Turning if off did not change my problem.  Also I can stand right next to it with my HT and get the '94 full scale.
       
      A trip down the street found with the HT confirmed that interference from 145.25 was coming from the exact same locations I was getting the most de-sensing from.  The noise seems to be coming from a length of cable coming from an amp at the corner of Edenbrook and Dorset and continuing to Hendrick and then fading away.
       
      I tried using a 440 Yagi to pin point the source but heard nothing.  The next step is to take a larger 2 meter Yagi to try to figure out if there is a problem with the cable or one of the two taps I see.  The noise is the loudest in front of one of my neighbor's houses and may be coming from inside.  A good directional reading is needed to figure that out.
       
      Thanks much Don!
       
      You too Alan,
       
      Mark K8MHZ
       
      ----- Original Message -----
      Sent: Saturday, August 12, 2006 17:15
      Subject: Re: [WestMichiganHams] Elusive interference

      Mark,
      Take a listen at the suspected trouble spot by listening to 145.25 on your 2 meter rig.  That is the carrier  frequency  for Channel 18 on the cable system.

      It sounds like what your are hearing is video.  That hum is what it sounds like on an audio (narrow bandwidth) radio

      73 de Don, WB8I

      k8mhz@k8mhz. com wrote:

      Calling all hams to put on their thinking caps....
       
      For quite some time now I have been having problems receiving 2 meter signals at my QTH.  For instance, the 94 will go from 60 over to down below the noise in an intermittent fashion.  This is confirmed by different radios and different antennas.
       
      Yesterday I made a discovery.  The source seems to be about 3/4 of a block from my house.  When I take my mobile or my HT there this is what happens:
       
      When and ONLY when I get a signal on 2 meters I hear a hum that is a bit faster then 60 cycles.  There is a point on Dorset street where the hum totally wipes out my 2 meter signal by de-sensing my radio.  I can watch as the 60 over signal from the 94 gets punched into the dirt by the hum, which is audible but does not register on the meter.  There is a point only a few feet wide on Dorset where I can stand or park and have my 2 meter rig's receiver totally wiped out.  Not intermittently either, it's nothing but a haspy staticy hum.
       
      Here is the weird part, as soon as the 2 meter signal drops, the nasty hum (audibly loud) totally disappears!  Even while standing near what seems to be the source of the problem.
       
      This makes it very tough to pin point.  I suspect a utility problem as the hot spot is right under a group of utility lines.  It has all of them, MV, LV, CATV and TX.  The lines look pretty good, no nasty connectors are visible.
       
      If I could determine how to be able record the noise without having a 2 meter radio signal present I would have a much better chance of figuring out the person or company to blame.
       
      The problem has got so bad that I routinely miss about a third of the Sunday Net as the interference takes out a word or two at a time.
       
      Today I am going to go look for some harmonics.  I am thinking it is possible that what I am hearing is a mix of compatible but different signals.
       
      Any help with my little adventure would be greatly appreciated.
       
      Mark K8MHZ


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