Alan,
Good point regarding a possible additive process that could
disproportionately affect a small signal; and I agree with all of your
points regarding phase, and add that the repeatability of NAA phase over six
or seven days measured, may elevate the likelihood of other phase error
sources. Like yourself, I am at a loss to imagine an ionospheric phase-error
source of this magnitude, slew rate, and localization that does not show up
in the Dst or other indicators, other than one associated with an
interference null. I smoothed the WH2XBA/1 traces (amplitude and phase) by
eye, found the answer that I wanted, and decided that I had been subjective
in my smooth-by-eye process. I'll try again this morning while look at the
small NAA features that you mention as potentially corresponding to WH2XBA
features.
Thanks for your comments. It would be nice to wrangle these photons.
73, Jim AA5BW
-----Original Message-----
From: [email protected]
[mailto:[email protected]] On Behalf Of Alan Melia
Sent: Sunday, March 9, 2014 5:59 PM
To: [email protected]
Subject: Re: LF: Daytime 29.499 kHz
Hi Jim I have been pondering those plots, but beware they are "relatve
amplitude" I'm not quite sure what Paul means here but the big swings on a
small signal v small swings on a big signal may not be significant. I
presume that the amplitudes are logaritmic (dBs)
The phase swing is harder to explain. We really need a close in station
monitoring NAA phase to be sure, but it could just be an antenna retune? I
tend to the feeling that sudden changes dont happen in nature :-)) just when
a fidgety hand comes into play. Only really the phase plots give us definite
changes the ionosphere.
I dont know how to explain this but (and it may be wishfull thinking :-) )
I think I see small upward blips , and downward blips in NAA which seem to
correspond to the big upward and downward swings of Bob's signal in the
night-time period. One would not expect them to be exactly the same as the
paths are a different length and the frequencies are different. The effect
on the amplitude is greatly affected but the mix of modes propagating ?? I
am not a great believer in averages but I wonder what it would look like
with a running average to smooth the XBA trace a bit. Though that would hide
he detail.
The daytime signal looks as though it might be too close to the noise to
follow the NAA "daytime dome shape".
Great bit of signal monitoring and processing.
Alan
G3NYK
----- Original Message -----
From: "hvanesce" <[email protected]>
To: <[email protected]>
Sent: Sunday, March 09, 2014 11:19 PM
Subject: RE: LF: Daytime 29.499 kHz
> Paul,
>
> With each piece of data (your NAA/WH2XBA 3-day amplitude below) this
> becomes
> more interesting.
>
> Summarizing some previous discussion and thoughts:
> NAA amplitude and phase are stable and repeatable night to night
> (amplitudes
> stable and repeatable within +/- 1dB across 3 nights).
> On two successive nights WH2XBA amplitudes are reduced and less stable
> (less
> stable even after normalizing amplitude stability for SNR), and are
> accompanied by premature, fast phase swings (2-hour transitions) of ~120
> degrees.
> If I think of ionosphere, oscillator phase, long-path ground effects,
> antenna and weather, my thoughts are slightly biased toward antenna and
> perhaps some secondary weather/temperature effect on the antenna, as you
> and
> Bob had considered.
>
> I'm glad that you noticed premature and fast 120 degree phase swings on
> successive nights, in contrast to stable phase on a (relatively) nearby
> path. That is intriguing on its own, especially in the absence of
> indicators in the Dst and other indices.
>
> Much appreciation to Bob, yourself and others for making these questions
> possible.
>
> 73, Jim
>
> -----Original Message-----
> From: [email protected]
> [mailto:[email protected]] On Behalf Of Paul Nicholson
> Sent: Sunday, March 9, 2014 12:44 PM
> To: [email protected]
> Subject: Re: LF: Daytime 29.499 kHz
>
>
> Jim wrote:
>
> > was the quick phase change of 120 degrees > corrected prior to
> integration?
>
> I'm plotting the signal in 20 minute integrations so there isn't much loss
> due to the phase change.
>
> We had about 120 deg phase change on the night of 6th/7th but it took 6
> hours, not 2.
>
> Here I plot three nights of opera alongside NAA for comparison of
> amplitudes
>
> http://abelian.org/vlf/tmp/29499_140309b.gif
>
> --
> Paul Nicholson
> --
>
>
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