[SBE] Looking for possible interference when siting a dish --

[George Nicholas]

Back in the analog audio days, I remember our Learfield sports network audio would get occasional "motorboat" type sounds in the background.  We tried all kinds of dish/LNB alignment and filters.  Of course, it got worse during night games.  It turned out to be an adjacent transponder with network video on it, and every time they showed a red graphic, it would modulate interfering audio.

gn   
  ----- Original Message ----- 
  From: Bill Burckhard 
  To: 'sbe member discussion mail list' 
  Sent: Thursday, February 26, 2009 1:47 PM
  Subject: Re: [SBE] Looking for possible interference when siting a dish --


  We had intermittent interference here for a long time. It was only on one transponder. We finally figured out that the fast food restaurant next door had a leaky microwave oven!



  William R Burckhard

  445 South 24th Street West

  Billings, MT. 59102

  (406)652-4743

  billb at khmt.com

  www.yourbigsky.com

  -----Original Message-----
  From: sbe-bounces at sbe.org [mailto:sbe-bounces at sbe.org] On Behalf Of Edwin Bukont
  Sent: Tuesday, February 24, 2009 1:51 PM
  To: sbe
  Subject: Re: [SBE] Looking for possible interference when siting a dish --



  Radar detectors and some vehicle anti-collision systems also apparently can cause issues.  TV station here went nuts with that problem until someone noticed it only happened when one particular car parked in front of the dish at the perimeter fence.

  Edwin Bukont CSRE, DRB, CBNT 
  Comm-Struction and Services LLC 
  Baltimore/Washington DC
  V- 410.879.5567 F- 410.272.5750 C- 240.417.2475 

  A Harris Broadcast Channel Partner 
   
  The opposite of PROgress is CONgress



   


------------------------------------------------------------------------------

  From: mlangner at swcp.com
  To: sbe at sbe.org
  Date: Tue, 24 Feb 2009 13:31:08 -0700
  Subject: [SBE] Looking for possible interference when siting a dish --

  Hello all !!



  Potential C-band interference thread --



  All good answers.



  "Out here in the west" before we site a dish we do an RF survey of the site.



  Usually we use a sheet-metal horn and a spare LNB from the shelf hooked into a spectrum analyzer.



  Since this microwave stuff bounces so well, even if you have a company do a search for terrestrial microwave paths, you likely wouldn't find out about the bounces off tall buildings, etc.



  Another not uncommon C-band interference source impossible to predict -- but that you can measure -- is certain kinds of radar altimeters from aircraft.



  Here in Albuquerque, NM, one station's "look" goes right across the approach to Albuquerque International Sunport (Airport) for planes landing headed east.  Made us crazy several years ago, since it was so intermittent.  But one day a staff member was listening to the air signal outdoors, and observed it disappearing as a Southwest Airlines plane was right in line!



  A passive C-band filter ahead of the LNB "fixed" the problem.



  Still, one TV station here several years ago had no option but to shield its receive dish.  They shielded it, all right!  They dug a 10 foot deep hole in their back parking lot and stuck the dish down in the ground.  Poof!  No more TI (terrestrial interference.)



  You can also get absorptive panels with with to ring your dish if you have TI coming in pretty far "off axis."



  Last I knew we shared out C-band allocation with Ma Bell and whatever carriers have come along since.



  Moral of our little story?  Ya gotta measure it!  Then license it to protect yourself from new potential TI problems as the spectrum continues to get more and more users.



  Good luck !



  Mike Langner, CPBE

  Albuquerque, NM

  ________________________





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