noise canceller


Posted on Feb 7, 2014

Are you situated in an area where there is significant QRM/QRN noise (QRM: man-made noise and QRN: naturally occurring noise) present on the HF Band making it impossible to receive weak signals Why not try building this noise canceller which nulls out and attenuates RF noise and interference with up to 40dB (typical). This includes noise from sou


noise canceller
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rces such as power lines, switching power supplies, TV ½s, computers, vehicle engines, etc. This circuit (refer to figure 1) is based on a design published in an article by Lloyd Butler (VK5BR). It works reasonably well at "nulling" out noise across the HF Band (from 1. 8 to 30 MHz). In practice I have been able to attenuate noise sources with as much as up to 5 to 6 S units which is equivalent to about 40 dB. This noise canceller is suitable for use with a receiver or transceiver and works on all modes, including AM, FM and SSB. The noise canceller is able to attenuate noise effectively on most frequencies using a RF noise antenna installed near the source generating the noise. In my experience a V-Beam or a single Delta Loop antenna used as the noise antenna pointing in the direction of the noise source works best. I initially tried a dipole antenna and a long piece of wire and both did not work effectively. V-Beam antenna ½s are directional and have about 3 dB gain over a dipole. A better alternative to a V-Beam is a single Delta Loop, in the vertical polarization configuration (the apex at the top, flat side horizontal to the ground and fed at one of the two bottom sides), which is also directional and has about 4 dB gain over a dipole with a lower take-off angle. A V-Beam antenna is basically an inverted-V antenna mounted horizontally. The V-Beam antenna should be mounted low to the ground (about 2 meters above the...




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