portegys@ihlpg.UUCP (Tom Portegys) (03/05/85)
I need help with an irritating noise problem. My neighbor and myself receive an intermittant signal on our TV and FM radio (I don't know about AM). The signal produces a band of small white dots on TV, and a buzzing sound on the radio. It can be seen on a number of TV channels. It also occurs on a portable radio held outside my house, so I don't think it is in the AC power. The noise also seems to occur without any pattern that I would associate with a ham radio, although I can't rule out that possibility. I have some power lines behind my house carrying residential power, and also a transformer on a pole back there. Can I track down the noise source with a portable radio? The radio has one of those telescoping antennas. If I could get the noise to sound louder when I hold the antenna in a certain position, how do I know which direction the noise is coming from? I would appreciate any advice. Tom Portegys AT&T Bell Labs Naperville, Ill. ...ihnp4!ihlpg!portegys
dsi@unccvax.UUCP (Dataspan Inc) (03/06/85)
Way back in the 70's (before EMI was a consideration) I encountered the
same problem fouling every attempt to make a tape recording. I have also
encountered this whilst working for a radio station.
A good bet is 1) the thermostat in your clothes dryer. It is absolutely
amazing how much RFI/EMI this thing will make just arcing away under a 30 amp
220 volt resistive load. Some dryers have two (or more) for the various heat
settings, etc. If you decide to bypass this thing, be sure to use the appropriate
UL recognised component as the voltages can be very high here.
2) Ditto for electric blankets (but these usually go schpritt-schpritt at
a 1-5 hz rate).
3) The SCR used as a control element in the heater that evaporates the
kerosene off your non-plain paper copies. Old Minolta copiers are terribly
bad about generating the most OBNOXIOUS rfi you have ever seen. The field from
this unit was so strong that it coupled into the audio chain of an AM station
located at the other end of the building.
4) Is your noise only on low band VHF channels? Sometimes, a defective
HT insulator can make your life miserable. This is extremely hard to find and
sometimes requires going from pole to pole with an AM radio and giving said
pole a good swift kick (The technique to be used is not unlike that in
kicking out streetlights. Three steps back...) . A change in sound character
or modulation indicates you might have found it.
Find this best with an AM radio and turn off stuff one at a time in your
house. It will probably show up as above problem....HOWEVER, if you have
ALUMINUM WIRING, you might just have a more serious problem which should be
brought to the attention of a qualified electrician.
dyagwyn@brl-tgr.ARPA (Doug Gwyn <gwyn>) (03/09/85)
> ....HOWEVER, if you have > ALUMINUM WIRING, you might just have a more serious problem which should be > brought to the attention of a qualified electrician. Talk about understatements!