Pat, Dave and Dale,
Small bidirectional loop antennas such as the Pixel "magnetic" loop
are very effective at placing a deep null on a single vertically polarized,
ground wave propagated RFI source. They cannot null RFI from
multiple directions, nor can they null horizontally polarized RFI.
They have little to no useful directivity for ionospherically propagated
signals .
Antennas with high RDF, such as a relatively small 4-square receiving
array (65 feet on a side on 160 meters), are very effective for
reducing RFI from multiple directions and they also have excellent
directivity for ionospherically propagated signals.
73
Frank
W3LPL
----- Original Message -----
From: "Patrick" <wa4tuk-rf@comcast.net>
To: "Dale J." <dj2001x@comcast.net>, "David Harmon" <k6xyz@sbcglobal.net>
Cc: rfi@contesting.com
Sent: Sunday, March 23, 2014 3:23:22 PM
Subject: Re: [RFI] Noise cancellers....
Dave/Dale:
I was really interested in one of these a few years back but after
studying the various web pages devoted to magnetic loop antennas I was
left with more questions than answers about how they might help with
power line noise.
It's easy enough to see how a directional receive antenna would help.
And a steerable receive antenna for 30MHz down to below standard
broadcast might see a lot of use.
I've got probably three different line noise sources all probably
one-half mile and further away along with one really nasty fence charger
pop. None of these sources could be called near field.
None of these (at least at present) are bad enough to wage a campaign over.
So, do you think you are actually getting some rejection of line noise
or is the improvement in reception mostly due to the directional
properties of the antenna?
Pat
wa4tuk
On 3/22/2014 1:09 PM, Dale J. wrote:
> Dave,
>
> I've been looking at one of these. Do you use it in conjunction as a noise
> antenna for a noise canceler or alone? What if the signal you are trying to
> hear is in the null zone? I assume you have a small rotor for it?
>
> Dale, k9vuj
>
>
> On 22, Mar 2014, at 11:22, "David Harmon" <k6xyz@sbcglobal.net> wrote:
>
>> Because these noise cancellers did not work very well for me and required
>> constant fiddling I got a Pixel magnetic loop.
>> These units have the ability to null out plasma noise as well as being
>> non-responsive to power line type noise.
>> It is a receive only antenna about 40" in diameter mounted on a 10' conduit
>> in the yard.
>> It is portable as well....I can disconnect the coax and walk away in 26
>> seconds.
>> It has a broad band amp at the loop and I use a 18db DXE amp under the desk
>> to get the received signal equal to the main antenna.
>> The directivity increases as the frequency goes up.
>> It is expensive....$500 but if bought direct from Pixel it has a 30 day no
>> questions asked money back guarantee if you are dissatisfied in any way.
>> It is the difference between going permanently off the air or continuing to
>> operate.
>> I cannot stress how well this thing works.
>> It took my 20/9 noise to S1.
>>
>> 73
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