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Re: [IRCA] Are Broadside Nulls Deeper with Phased Active Loops?
Please indulge me here, but I'm wondering just how much of the S9+15 of noise you have is actually coming from LA at 40 miles away. Ordinarily city noise doesn't radiate that far at that level. This doesn't alter the basic question you've asked, but it might factor into the discussion of a solution. I suspect the high tension lines are the primary noise source, and while the single array has reduced the noise by 15db, you need more.
I am unfamiliar with the Wellbrooks other than a very basic second-hand knowledge. One other option might be a cardioid array, which can be achieved by phasing a loop and a vertical, and if indeed the majority of the noise is N then it's easier to deal with.
I would try taking the portable and going right up close to the lines to your North and following the level as you move toward your home, then go a similar distance to the South and compare the results.
Russ Edmunds
Blue Bell, PA ( 360' ASL )
[15 mi NNW of Philadelphia]
40:08:45N; 75:16:04W, Grid FN20id
<wb2bjh@xxxxxxxxx>
FM: Yamaha T-80 & Onkyo T-450RDS w/ APS9B @15'
AM: Modified Sony ICF 2010 barefoot
--- On Tue, 3/24/09, Roy H Norris III <royhnorris@xxxxxxxxx> wrote:
> From: Roy H Norris III <royhnorris@xxxxxxxxx>
> Subject: [IRCA] Are Broadside Nulls Deeper with Phased Active Loops?
> To: "IRCA" <irca@xxxxxxxxxxxxxxxx>
> Date: Tuesday, March 24, 2009, 2:42 PM
> Hi,
> I am new to the list. Although I am a ham radio guy, the
> knowledge on this
> list might be able to help me with an unusual problem.
> Forty miles to my
> south sits Los Angeles, the largest source of noise in the
> universe. To my
> north by two miles are very high tension power lines. My
> noise level on the
> 80 meter and 40 meter amateur bands is 15 dB over S-9! I
> have determined
> that the noise is not from my own house or any of my
> neighbors by shutting
> off power and using a hand held loop RDF.
>
> I want to be able to communicate primarily in an easterly
> direction. I can
> accomplish this if I can null out the noise coming from the
> North and the
> South. But with my present noise level, I can't hear
> anything. I plan to
> use separate receive and transmit antennas.
>
> 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.
>
> I would appreciate any thoughts or suggestions on the best
> configuration of
> a receive only antenna to deal with this problem. Since I
> will be using a
> separate transmit antenna running a lot of power (1,500
> watts) I am looking
> at building active loops using the amplifiers from DX
> Engineering's active
> whip antennas since they ground the inputs when powered
> down.
>
>
> Your thoughts and suggestions would be greatly appreciated.
>
> Roy Norris, K4EEG
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