[RFI] Guidance on finding noise?

[K9MA]

With any kind of direction finding antenna, you have to be aware of 
polarization. A vertically polarized loop, for example, may give very 
misleading bearings if the noise happens to be mostly horizontally 
polarized. When I walk around with my 135 MHz yagi tracker, I rotate its 
polarization as I sweep around in azimuth, and often find the most 
distinctive peak with it mostly vertically polarized.

73,
Scott K9MA




On 1/12/2020 15:18, AA5CT via RFI wrote:
>   This may be a case where the marine DF receiver succeeds, and a
> simple DF loop fails.
>
>
> With the simple DF loop one is unable, repeat, *unable* to resolve
> the __180 degree ambiguity__ that the 'null' of a simple loop gives.
>
>
> The BIG, and this is NO slight advantage offered by the marine DF
> receiver is the utilization of a "sense" antenna that works in combination
> with the built-in loop antenna to 'synthesize' a cardioid or unidirectional
> antenna pattern.
>
>
> WITH THIS feature one can actually 'sweep' around the compass rose
> and get a feel for where the strongest noise is coming from, like pointing
> a Yagi antenna around, but on 160 or 80 meters! On the other hand, the
> simple loop can ONLY give a one a NULL, and there remains the choice
> of which direction, which bearing the 'source' lines in, because of that
> 180 degree ambiguity.
>   
>
> Also with the simple loop one cannot 'scan around' for the strongest
> signal, whether that signal is a 'broad band' white noise (LIKE I get
> from a car wash in my area) OR impulse 'buzz' noise from power
> line arcing sources.
>
>
> IT REALLY IS pretty cool to 'twirl' the direction knob on one of these
> Coastal Navigator Marine DF receivers and HEAR the different 'arc'
> signatures or sounds coming from different directions.
>
>
> Maybe this is where we're getting hung up up? All my DFing for
> any noise nowadays makes use of the marine DF receiver with the
> sense antenna and that directional Cardioid pattern.
>
>
> If IT emits, its a simple matter of taking two bearings sufficiently
> spatially spaced apart and "x" marks the spot of the source. I now
> use Google maps and 'null' bearings taken from my DF receivers
> to pinpoint distant sources.
>
>
> One technique I've used too is to 'set out' after one of these sources on
> my trail bicycle, and through the use of null DFing and the Sense/Cardioid
> function eventually locate OR determine the source is further way than
> first thought. If I get down the road a mile or so AND the DF receiver is
> still indicating the SAME direction, I'm looking at a source that is now
> on the order of 4 to maybe 5 miles way, and as I've written, I've had a
> couple just like that!
>
>
> de AA5CT
>
> .
> .
>       On Saturday, January 11, 2020, 9:03:04 PM CST, Kenny Silverman <kenny.k2kw at gmail.com> wrote:
>   
>   KC4D,N3AC and N3CW went hunting with a KX3 and a DX Engineering Amplified RX loop and again didn’t find anything conclusive. Basically they said the loop performed about the same as one of the AM radios we have that’s fairly directional.
>
> We’ve been looking so many times that we’re getting frustrated.  There are a few noisy clusters, but we can’t find a specific pole or house.  Nor can we assess if the noisy areas are actually the key offender(s)
>
> Do we call in the clusters we found ?  Or do we really need to pinpoint the source(s) better before we ask for crews to come out?  We’re concerned about crying wolf and/or giving a list of more than a dozen poles for the power company to look at.
>
> Regards , Kenny K2KW
>
> P.S.  the only success so far is fixing my subject line typo 🤓
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-- 
Scott  K9MA

k9ma at sdellington.us