Just as a follow-up, a cardioid pattern can be broken into parts. It is equal to the combination of a vertical and a loop antenna. Adding another loop antenna to mix would probably just make the main lobe of the original cardioid even wider with slightly less pickup in the center of the main lobe. Oh well, it was a thought...
73, Chris -----Original Message----- From: [email protected] [mailto:[email protected]]on Behalf Of Chris Knight Sent: Wednesday, January 28, 2009 10:49 AM To: Mailing list for the International Radio Club of America Subject: Re: [IRCA] ALA 100 Hi Steve, Nick, et. al, The ALA100 sounds like a great antenna! Some observations/thoughts... Each antenna has its (dis)advantages. The 17'x37' corner-fed loop here is very quiet, but has a broad lobe (= more splatter). Signals aren't as strong as a bi-directional loop, but they are quiet. The corner-fed allows almost nightly reception of Spain-639. A bi-directional loop (i.e.: ALA100) would not, since pest KFI on 640 is smack in the opposite lobe. The corner-fed also has a narrow, but very effective null that will entirely null any one of my locals. And, it does a great job nulling KFI's sky wave signal. The cogs are turning (WD-40 may be needed)... Guy Atkins posted a couple of small loop configurations, rotatable with a TV rotor such as a Channel Master or similar (I've gotten these on ebay for cheap). It would be possible to build a generic, 10'x10' loop (or smaller), match it with a 1:1 transformer and rotate that setup on one end of the yard (or house). At the other end, rotate a slightly larger, rectangular, corner-fed loop (~16:1 transformer). Broadband amplification would be needed for both antennas (especially the corner-fed) and could possibly be handled with a Quantum Phaser (or similar), either alone or in combo. Next, to hear Spain on 639, one could aim these antennas Southwest/Northeast (from Colorado). The corner-fed loop lobe would point SW toward the pest station (KFI), its null positioned toward Spain. Both antennas would produce lobes in the SW direction. The Quantum Phaser would come to the rescue and phase-cancel the nearly equal SW lobes (little adjustment required - important!) leaving Spain on 639 stronger than what it normally would be on just a NE corner-fed. The remaining phase-cancelled pickup would be almost entirely from the NE lobe of the bi-directional loop - at least in my mind it would be or am I assuming too much? Supposing this works, would it approximate the pickup from a phased BoG system? Or (and I think this matters) is the spacing of the 2 above antennas critical? If so, the BoG remains the winner since, as a traveling-wave antenna spacing isn't too critical. Speaking of BoGs, they take up less space than a Beverage antenna and when phased they either equal or beat a Beverage in terms of DX performance. Neil Kazaross' stellar loggings attest to that. No room here for one, unfortunately. :-( I would love to stumble upon/design an antenna setup that would emulate a BoG system, that could easily fit in my 50'x60' backyard. Having the ability to control direction and angle of signal pickup would be a plus...hi. (like a mini Wullenweber antenna) Cogs still turning (squeak, kah-thump), the next thought is a sloper toward the pest station phased against an ALA-100, for example. Would that work better as a phased combo? (think patterns and signal strengths) Another thought: How about a phasing unit with independent antenna amplification and linear gain control? This could be the key to making steer-able backyard BoG emulation work and should be easy enough to design if it hasn't been already. Comments, critiques, alternative suggestions, etc. are appreciated! 73. Chris Knight Fort Lupton, Colorado _______________________________________________ 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]
