[RFI] Portable DFing at HF

[Tom Thompson]

Kelly and all,

My experience has been that local HF RFI is almost always vertically 
polarized unless you are very very close to it.  This means that the 
null is looking through the loop.

My last RFI hunt took lees than 15 minutes.  I took a reading and 
determined the two directions the RFI could be coming from.  I then 
walked about 100 feet perpendicular to the direction line and resolved 
the direction ambiguity.  Walking another few hundred feet while 
twisting the loop for maximum signal located a Hobart Flex 180 battery 
operated welder in the garage of the house next door.  By the way this 
was not my neighborhood.  The ham I was helping is in the process of 
resolving the problem with his neighbor.

Tom   W0IVJ


On 8/12/2016 11:56 AM, Jim Brown wrote:
> In off-list email, Kelly has said he thinks is noise is from a grow 
> operation, so I think he has to DF it on the HF band(s) where he hears 
> it. That means loop, so something like what W0IVJ has posted is 
> probably the way to go.
>
> Another important suggestion -- a spectrum display is usually the best 
> way to nail down whether it's impulse noise or electronic noise, but I 
> don't think Kelly has one.
>
> 73, Jim
>
> On Thu,8/11/2016 9:24 PM, KD7JYK DM09 wrote:
>> :I am trying to locate a new source of RFI in my neighborhood.  I can 
>> get a
>> : decent direction in it from my yagi, but would like to DF it from 
>> another
>> : direction to pinpoint the source.  I don't know if I can DF it at 
>> VHF or
>> : UHF, but the noise is very clear on 20m.  Any ideas about a good 
>> portable
>> : DF antenna for 20m?
>>
>> I DF up to 950 MHz for two reasons.  One, small directional antennas, 
>> two,
>> they usually aren't needed because as the frequency goes up, the 
>> distance
>> goes down and you can usually narrow a source to a few feet at that
>> point.  What kind of VHF and UHF equipment do you have that can 
>> receive in
>> AM?
>>
>> Kurt
>>
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>
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