> Alan
> Does the Flag loop antenna hear noise
> ( Noise Sense Antenna ) better than say a
> Small 2 foot Magnetic Loop That resonates at 40meters ?
>
> Trying to use a loop than say a Magnetic Loop
> or a Vertical Mobile CA-HV 40meter coil type HF Whip with a DXE NCC-1 that
> acts as a noise Cancellation system with Amplitude and Phase
> adjustments
>
> Any comments appreciated
>
> Mike
> WB6DJI
>
>
>
>
> Sent from my iPhone
>
>> On Apr 12, 2021, at 8:57 AM, Alan Higbie <alan.higbie@gmail.com> wrote:
>>
>> In the past few days I've started using a Flag Loop antenna (designed by
>> WD8DSB).
>>
>> I supplement it by also using a National RF HF-DF bidirectional loop.
>>
>> The patterns on both have been confirmed by using a known signal source (RF
>> signal generator).
>>
>> Having a unidirectional antenna is very helpful. The null of the
>> cartioid pattern is quite pronounced.
>>
>> Example: for years now, I have had a noise source which seemed to be coming
>> from 40 deg. at times - and other times coming from 220 deg. I believe
>> that the results had been confounded by re-radiation along the power lines.
>> Now
>> I have now definitely determined that it is from 220 deg. (i.e. a giant
>> step closer to location and resolution).
>>
>> An ** interesting feature ** of the Flag Loop is that it is broadbanded -
>> maintaining its directional properties over a big chunk of spectrum.
>> Unlike a tuned loop (or tuned yagi), a broadband antenna allows you to view
>> a huge piece of spectrum at once. And with an SDR this is quite easy - and
>> very interesting.
>>
>> Dave, NK7Z, has a blog where he describes using an SDR to make site RFI
>> survey. He was using a fixed broadband antenna.
>>
>> Look at Dave's work on this subject:
>> https://www.nk7z.net/rfi-site-survey-part-ii-interpretation/
>>
>> Having a broadband and unidirectional ROTATABLE antenna allows us to
>> quickly and more definitively see associations among the various sources.
>> And, simultaneously begin to find the RFI source.
>>
>> Yesterday I set my SDR to receive a section of spectrum from 3.0 to 11.0
>> MHz. Then I rotated the Flag Loop - - and the results were very
>> interesting: I could see some very strong and wide signals. These
>> appeared across the spectrum and which rose-and-fell together (meaning they
>> are from the same device). I had not realized that junk was there.
>>
>> Still don't know if these wide signals are ACTUALLY AFFECTING MY RECEIVER'S
>> NOISE FLOOR on any band. To be determined. Interesting nonetheless.
>>
>> *Why this matters*: a broadband / unidirectional antenna with SDR now
>> allows a view of what kind of RFI is really out there.
>>
>> 73, Alan K0AV
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