[RFI] Guidance on finding noise?

[Grant Saviers]

A couple of comments:

I just bought ($25) a Marine DF, with BFO, 3 bands 0.15 to 5MHz, & VHF 
FM, has D battery as well as 12v.  Optical sights, S meter, sense 
antenna as well!  Pretty good RFI DF I think. Aqua-Guide CH-704 Marine 
Direction Finder.  If anybody has documentation, a copy would be greatly 
appreciated.

A nearby pole had its ground wire cut and the remaining length was a 
perfect length as a 40m vertical.  PSE was quick to fix it when logged 
as a safety problem.  However, the "ground" for a pole might be a single 
rod or a spiral wrap of the wire when the pole was dropped into the 
hole, so ground wires are likely decent radiators.

I also have a Lokata 7 LF/BCB DF handheld from my way back sailing days, 
a top rated handheld DF, digital freq readout but it is dead, so also 
looking for schematics for it.

Grant KZ1W
Redmond, WA

On 1/13/2020 03:51, AA5CT via RFI wrote:
>   Scott,
> 
> 
> The marine DF receiver (with the "sense" antenna to give a
> cardioid pattern) in use by myself (and a few others) covers
> the old "marine" band as shown on the scale as 1.6 MHz
> through 4.0 MHz and _not_ the (now) traditional VHF band
> (using FM) near 156.8 MHz ("CH 16").
> 
> 
> Also it's rx mode is AM. Sorry for the confusion.
> 
> 
> I have used it with the ferrite loopstick vertically oriented
> (for horz polarization) and reception goes to nil in that case,
> so it works out just fine leaving it oriented for incoming
> vertical plane waves.
> 
> 
> When "inspecting" a noisy pole with the UHF beam I do note
> a difference when rotating the beam; this is trivial to perform
> but does show that various 'elements in the structure' (wires)
> are preferential to the radiation of the RFI 'noise' over others
> at the much shorter UHF (450 MHz) wavelengths (a factor of
> over 100 'shorter' over the wavelengths of the old "marine"
> band.)
>   
> 
> The hypothesis (my hypothesis) to the radiation of power
> line noise (___for the HF low bands____) is the ground wire
> running along the pole does the majority of the "radiating".
> Just imagine a T-top vertical antenna; that antenna is a
> vertical radiator and the opposite 'currents' in the T-top
> wire generate magnetic fields opposite in direction. The
> T-top wire is the active phase line(s) involved in the creation
> of the noise, and it could also include the neutral wire.
> 
> 
> If you've ever seen the demonstration video by N4IS (Jose
> Carlos) of the large Waller Flag (works on 160m and 80m)
> you will note when he rotates the flag horizontal ALL the
> (what sounds like) power line noise __goes away__, leading
> one to conclude that the majority (if not all) of the local
> low band HF/MW (160m and 80m) 'noise' is vertical in nature.
> 
> 
> de AA5CT
> .
> .     On Sunday, January 12, 2020, 11:12:47 PM CST, K9MA <k9ma at sdellington.us> wrote:
>   
>   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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> 
>