[AMRadio] Noise Source Discovered


doxemf at aol.com doxemf at aol.com
Thu Jan 12 12:58:37 EST 2006


Hello Guys,
  With the onset of the winter heating season here in the Northeast a new nasty buzzing  and periodic noise cropped up right in the middle of the AM "Window".
  At first it was thought to be from some of the seasonal lighting put up around the neighborhood but as it continued after the stuff came down a little research was needed.
  A spectrum analyzer put on the IF showed a wide and strong signature similiar to high voltage arching
but also had a serious line synched short 20db+ spike riding on it. 
  I grabbed a DX-390 portable receiver and tuned around and had no problem finding the noise as it was all over the place.
  A walk around the building located it to the recently installed Solid State oil furnace high voltage transformer! The thing is about half the size of the old standard one and encased in only a plastic housing. While the noise generation coupled to the AC line was visable to a large degree it was primarily on the positive half of the AC waveform only. A nasty burr similiar to the signature of lamp dimming triac phase control. The main radiator tho was the thermostat wire !!.
  This little noise box appears to not have the FCC type acceptance label and for all I know might be exempt but is one heck of a noise generator. Probably a high frq switching type supply.
   Have yet to figure out just what to do about this but am tempted to go out and just buy a normal transformer rather than try to explain the problem to the oil company who replaced it to begin with.
  So if you have had a similiar problem crop up this info might be of some use. 
 
Bill  KB3DKS/1



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