At 18:42 3/24/2009, you wrote: >I am currently using a Wellbrook ALA-330S loop to cut the noise down to S-9 >by placing the broadside of the loop in the N-S direction. Could I get a >deeper broadside null (figure eight pattern) by phasing two or more active >loops positioned with the planes of the two loops running North and South >and separated by 1/2 wavelength? Is there another configuration of two or >more loops that could be phased by separation and one of the adjustable >phasing devices such as the DX Engineering NCC-1 or the MFJ1025 that would >give me a deep broadside null to the preferred direction of communications >(East)? (Of course, being able to communicate in more than an easterly >direction would be nice but I can't see how to do that as I would need a >steerable antenna system (electrically or physically) with very deep fixed >direction broadside nulls. ) > >The write up on the Wellbrook phased array: >http://www.wellbrook.uk.com/phasedarray.html shows a pattern similar to >what I want to achieve with two loops at 180 degrees (1/2 wavelength >separation, I believe they mean) and fed with zero phase setting. But since >they do not compare the results of the phased array with a single loop, I >cannot tell if the broadside nulls are deeper with the phased array.
Awhile back I measured an ALA100 preamp using a somewhat smaller loop than what Wellbrook suggests, Roy...the null on a single loop was somewhat greater than 30dB, which agrees with theory, and may well be what you're getting already. However, what Wellbrook shows with their phasing unit and 1/2 wavelength separation is a greater than 40dB null, and the pattern is less rounded than a single loop, so would be more directional east-west. For example, they show a signal would be down 6 dB at 45 degrees, while my single loop gave more like 3dB at 45 degrees. With the phasing unit, you might be able to play the null a bit to attenuate your noise further, but no guarantees....especially as it seems you can't put a single null on it at present (i.e. it's not a point source). best wishes, Nick ***************************** Nick Hall-Patch Victoria, BC Canada _______________________________________________ IRCA mailing list [email protected] http://montreal.kotalampi.com/mailman/listinfo/irca Opinions expressed in messages on this mailing list are those of the original contributors and do not necessarily reflect the opinion of the IRCA, its editors, publishing staff, or officers For more information: http://www.ircaonline.org To Post a message: [email protected]
