[Lowfer] Noise Canceler Effectiveness... How it REALLY works ??

[Bill Ashlock]

Jay,
 
I looked at the URL on terminated loops and their cardioid pattern. It's kind of hard to analyze the antenna by removing the resistor and not completely change the antenna but it seems to me that the terminated loop is simply an E-field antenna in series with an H-field antenna. The current resulting from the incoming E-field produces a voltage across the resistor that is added to the voltage produced by the figure "8" H-field and the net result is a cardioid response. But maybe we are simply arguing semantics? 
 
One might be able to prove my theory by installing a delta-shaped loop and a long wire antenna of equal dimensions to a reference terminated loop. If the outputs are properly combined in phase and amplitude the same reception characteristics should be attainable. Another possible hint that my theory is correct is that these antennas continue to work with minimal ajustment as the frequency is lowered. I think this is because the E-field and H-field reception patterns do not change. But when the loop gets close in size to a maybe a 1/8 of a WL, where the loop would begin showing multiple lobes, the cardioid pattern would not be possible.
 
Bill



From: jrusgrove at comcast.netTo: lowfer at mailman.qth.netDate: Wed, 14 Jan 2009 18:42:49 -0500Subject: Re: [Lowfer] Noise Canceler Effectiveness... How it REALLY works ??



Some info on terminated receive loops is available at http://www.w3eee.com/ ... scroll down to receive antennas.
 
I use a large K9AY for 137 and 500 kHz. A drawing of the antenna is available at http://www.w1vd.com/k9ay11.pdf. The Vactrol terminating resistor is adjustable from the shack. I find that the resistance required for optimum front to back is the same regardless of the direction selected. The antenna maintains excellent directivity as one goes lower in frequency  -  at 60 kHz the F/B is 20+ dB - same as it is at 137 and 500 kHz. Directivity falls off at frequencies greater than 1 MHz.    
 
Jay W1VD  WD2XNS  WE2XGR/2

----- Original Message ----- 
From: Bill Ashlock 
To: lowfer at mailman.qth.net 
Sent: Wednesday, January 14, 2009 5:06 PM
Subject: Re: [Lowfer] Noise Canceler Effectiveness... How it REALLY works ??
Hi Alan, I think this antenna is far too small (WL wise) to have the properties you describe. The basic antenna looks like a small loop and a E-field sensing antenna to me and I believe the resistor is introducing what is sometimes referred to as an "Antenna Effect" or an undesired susceptibility of a loop to the E field, which tends to modify the figure "8" pattern - but in this case it is adjustable and becomes a desired effect. Any comments from others? Bill > From: alan.melia at btinternet.com> To: lowfer at mailman.qth.net> Date: Wed, 14 Jan 2009 14:39:24 +0000> Subject: Re: [Lowfer] Noise Canceler Effectiveness... How it REALLY works ??> > Hi Ok on the loops but this form of noise canceller works with two end fed> wire antennas too...... which dont have "fig of 8" patterns !!> > On the K9AY I have reservations about that explanation too because the K9AY> is not a loop....it is more like a travelling wave antenna. It may be the> model works, but I prefer to compare it with a coupled line. Think of a> directional coupler only here the coax/waveguide is the earth ionosphere.> Then the coupled line is a line terminated in a resistor where a signal> from one direction is absorbed in the matching resistor. The matching> resistor need changing depending on the direction in the K9AY ....varying> the orientation of a pick-up loop in coax changes it impedance, and so> requires a different termination. Any comment ?? There are elements of this> in a Beverage too.> > Alan G3NYK> > > > _______________________________________________> >From the Lowfer mailing list> Send messages to: Lowfer at mailman.qth.net> To sub/unsub visit: http://mailman.qth.net/mailman/listinfo/lowfer



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