I've located the source of HF interference in the past by getting a beam
heading with my 20m yagi, then walking that direction with an FT-817 tuned
to 50MHz. For powerline noise, I then pull out a portable (Arrow) 432MHz
yagi to really pin it down to a pole. The last time I had a noise like the
one that I'm hearing now was DF'd with my 20m yagi and the FT-817 tuned to
50Mhz. This time, the source appears to be across a freeway in another
neighborhood. I was hoping to reduce my neighborhood walk time by using a
second directional antenna to triangulate the source. Unless the noise is
extremely loud, I wouldn't expect the loop to even hear it until I get
close. What I'd really like is a 20m yagi on a portable tower that I can
drive a block away and use to triangulate the source. I think that would
work the best, but that's not a very practical option.
On Fri, Aug 12, 2016 at 11:09 AM, Tom Thompson <w0ivj@tomthompson.com>
wrote:
> 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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>>> RFI@contesting.com
>>> http://lists.contesting.com/mailman/listinfo/rfi
>>>
>>>
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>>
>>
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