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On Apr 8, 8:09*am, bpnjensen wrote:
On Apr 8, 5:23*am, dave wrote: On 04/07/2011 10:26 PM, bpnjensen wrote: * * p Hmm - do you have QRM at your cabin? *My guess is that, the more rural (and QRM-free) the setting, the less useful a set of phased antennae would be. They don't work on atmospheric/QRN noise very well. *MFJ and Timewave says they work on things like lightning crashes, but you'd be very hard-pressed to twiddle those knobs fast enough to use it for that purpose. Having said that, two DX-Ultras phased together for noise abatement might be just dandy, and they don't require grounding for exemplary results. Bruce It depends. If all the QRM is coming from one t-storm cell, or a line 500 miles away, you don't have to adjust that much. I've always lived in a neighborhood and have had excellent DX catches in spite of the power lines and dimmers. The reason I use verticals is that they have reduced response to things below about 15 degrees elevation. The MFJ-1056 is handy for steering a null toward a single noise source and doesn't require a full size "noise' antenna. That's why the "noise" antenna has a preamp. My "noise" antenna is actually farther from Dewey's RV than my "main" antenna, but it still does its job. True, Dave, but the closer the noise antenna is in general electrical characteristic to the main antenna, I believe, the better phasing ability you'll get. For awhile I used the tiny noise whip that came on the 1026, and it actually worked better than one might expect, especially on 60 meters - but the few antennas I have had since than have progressively improved on that, and less preamping I need to use on the noise antenna, the better the results seem to be. The vertical idea is very intriguing. *I have heard, maybe erroneously, that verts capture more QRM due to its inherent polarity; but I can imagine that two verts pumped through a 1026 might be a really great set-up if the sources of QRM are limited. Bruce *IF* Your main RFI/EMF Noise Sources are External to your House an 'Outside' Vertical Noise {Sense} Antenna usually works better than the Built-in Whip Antenna. -however- *IF* Your Your main RFI/EMF Noise Sources are Internal to your House the Built-in Whip usually works well as the Vertical Noise {Sense} Antenna. Basic 'Outside' Vertical Noise {Sense} Antenna : Connecting a "Snake" {50 foot Coax Cable} Antenna that ends in a Vertical Section with a Bottom 5-12 Feet of Coax Shield and a Top 5-12 Feet of Inner Conductor to the MFJ-1026's Rear SO239 AUX ANT Jack. http://www.universal-radio.com/CATAL.../3542rear.html [Total 10~25 Foot Vertical Noise {Sense} Antenna] Place a Clamp-On Ferrite Bead at the Base* of the Vertical Section. * Very Near Ground Level Relative to your Main SWL Antenna your Vertical Noise {Sense} Antenna can be moved around to find the best location where it picks-up the most Noise to do it job : Right-Side [Out=L/2] Center; Left-Side [Out=L/2] Center Far-End [Out=L/2]; Near-End [Out=L/2] -if- You have an Identifiable 'Outside' Noise Source having the Noise {Sense} Antenna Closer to the Noise than the Main SWL Antenna can make it more effective and produce better overall results. -note- Out=L/2 : Try to get the Vertical Noise {Sense} Antenna "Out" and Away from the Main SWL Antenna by about Half-the-Length "L/2" of the Main SWL Antenna or at least Half-Way between the Noise Source and the Main SWL Antenna; that is within the confines of your property. -better- "Out" and Away is "L=1" iane ~ RHF |
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