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Re: [IRCA] Are Broadside Nulls Deeper with Phased Active Loops?
If this noise is 24/7, it's probably coming from power co. equipment & probably nearby. If you can start to pin down the area, walking around with a portable radio, or driving around using a radio in the car, that would be a good start.
Just put the radio on a dead spot or weak broadcaster & notice where the noise is strongest. If possible start with the highest frequency that you can hear the noise on & note that, & which direction from your house does the noise continue & how far.
Then call your power co, & ask for the radio frequency interference expert. If your power co doesn't have the needed equipment to track down the precise spot, they probably can call the power co that serves an adjacent area.
My power co, which serves parts of 4 counties, takes RFI very seriously. Valuable electricity is probably escaping. My power co has replaced over 8,000 insulators. I had HF interference over a 1 block area. He detected the noise above 300 MHz! It was the insulator near the corner of our yard. Hope this helps! 73, George S., MN
--- 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, 1:42 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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