I have a more reliable SA on my bench, I will be doing some compairs to
the tinySA, although there is a fellow on YouTube that used a decent HP,
and the tinySA is fairly decent if you watch input levels... I have a
preamp I am building for the mess... I want a small single box I can
put on the antenna... :)
73, and thanks,
Dave (NK7Z)
https://www.nk7z.net
ARRL Volunteer Examiner
ARRL Technical Specialist, RFI
ARRL Asst. Director, NW Division, Technical Resources
On 4/12/21 1:44 PM, Alan Higbie wrote:
Dave ~
Adding a spectrum analyzer should be interesting.
Getting it all configured for easy use in the field is the next logical
step.
I hope it is broadbanded. While the SWR measured 1.1 to 1 from 160 past
10 meters . . . I'm not sure that means it is truly broadbanded.
When viewing a power line source I noticed that its strength was not
uniformly the same across the 9 MHz I was looking at. However, that
could be caused by resonance along the power lines.
I don't know - but it's all getting easier than it used to be.
~ Alan K0AV
On Mon, Apr 12, 2021 at 1:56 PM Dave Cole <dave@nk7z.net
<mailto:dave@nk7z.net>> wrote:
Hi,
You sir are a mind reader, I just started working on a FLAG for just
this sort of setup-- portable use of a broadband antenna.
I am happy to hear it is as broadband as you say... I will be
taking it
and my SDR on a few walking trips soon...
Being able to see 10 or so MHz. of spectrum is enlightening as hell
once
you start seeing your RFI on more than one band at a time... When you
dip one source, you see many signals dip at the same time, and you
realize they are all related! That and they all look the same, just
shifted in frequency. :)
That blog post you cited, (and thank you for that), is part II of a
three part blog entry...
Part I covers setup and use of the SDR for this sort of thing, and
is at:
https://www.nk7z.net/sdr-rfi-survey-p1/
Dave (NK7Z)
https://www.nk7z.net
ARRL Volunteer Examiner
ARRL Technical Specialist, RFI
ARRL Asst. Director, NW Division, Technical Resources
On 4/12/21 8:56 AM, Alan Higbie 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
> _______________________________________________
> RFI mailing list
> RFI@contesting.com <mailto:RFI@contesting.com>
> http://lists.contesting.com/mailman/listinfo/rfi
>
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