Over the Air -Antenna interference

[Dahillbilly]

discovered the following & wondering if anyone knows a way to resolve the problem; While using the King OTA roof antenna pictures are nice clear UNTIL the roof vent fans are turned ON, the more fans I turn on the more static/interference on the screen to the point you cannot watch the TV. Once the fans are turned OFF you have a clear picture. Has to be something with the 12VDC motors causing the issue.

 

[Bogie]

I think your are experiencing EMF generated by the DC motors. You might try adding Ferrite cores to the wiring close to the motors. Also might add one to the wiring of the antenna amplifier.

Like these.... These

 

[wdk450]

The small DC motors typically use commutator brushes to supply the right polarity of current to the armature coils as it rotates. This causes arcing with every current switching reversal, and electrical arcing causes wideband electromagnetic noise. Marconi used an electrical arcing source to send the first transatlantic radio communications.

You can try wiring across the motor a small ( something like a .001 pF ceramic 12 volt) capacitor to "short out" the RF noise while not affecting the 12 volts DC to the motor.

Newer, more expensive, small DC motors have eliminated the contact brushes with a solid state device called a Hall Effect switch that turns on and off under the influence of a magnet's field and doesn't produce RF noise.