Return to KLUBNL.PL main page

rsgb_lf_group
[Top] [All Lists]

LF: Re: DHO Link

To: <[email protected]>
Subject: LF: Re: DHO Link
From: "Markus Vester" <[email protected]>
Date: Sun, 16 Mar 2014 18:05:14 +0100
Authentication-results: mx.google.com; spf=neutral (google.com: 195.171.43.25 is neither permitted nor denied by best guess record for domain of [email protected]) smtp.mail=[email protected]; dkim=fail [email protected]
Delivered-to: [email protected]
Dkim-signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=mx.aol.com; s=20121107; t=1394989525; bh=y/bAu/4egPsOzJF5XdeW7s8QyJB0ad1uN8v49y89KMg=; h=From:To:Subject:Message-ID:Date:MIME-Version:Content-Type; b=BrAl2m+ZNefxdzXafcHaxmTJkKyPHyj0daJ8BTHHin+hPQ/FKxvGoWf12tM5qRXEn CqWHo7qdshGdmB/chHnEv0ycYA89rv7M0W6bh0EWi2liMdpQamUP73HD4p2jKxV3at WPlkO0kxRS39tpZHdvO5J91Xgy2UhLhuUA+qKTY0=
In-reply-to: <[email protected]>
References: <[email protected]>
Reply-to: [email protected]
Sender: [email protected]
Jim,
 
thank you very much for pointing out the online papers. I'll take my time to read them, and (though being an engineer not a physicist) will at least try to conceive the main lines of thought. Not sure if I understand zenith angle dependence of the beta parameter - is this not just an electron density gradient, vertically measured?
 
I am also wondering how to make quantitative use of the long / short path fringe patterns, which are so easily observed in spectrograms of NWC 19.8 kHz in Europe.
 
BTW Jim are you planning to start transmitting on VLF yourself, either 29.5 or below 9 kHz ?  
 
Best 73,
Markus (DF6NM)
 
----- Original Message -----
From: hvanesce
Sent: Sunday, March 16, 2014 2:39 PM
Subject: LF: DHO Link

Markus,

 

Thanks for the DHO diurnal plot.

 

It?s a memorable image, with interesting symmetries.

 

I remain hopeful of finding or making a model that qualitatively represents VLF amplitude and phase diurnals for a substantial percentage of cases. This would be very helpful in preparing for DX, QRP and other activities.

 

Thomson has done some great work in this area (VLF diurnals). I was surprised to find that he reverted (prior to 2011) to Wait?s 2-parameter ionospheric reflection model (using h and beta*, and adjusting them empirically), instead of using LWPC or ModeFinder (which he mentions require more knowledge of ionospheric parameters than is currently available:  http://www.physics.otago.ac.nz/space/Thomson_LongPath_paper_JGR_2011.pdf ; I thought Paul might also find this point interesting)

 

To make matters more interesting, Han (http://people.ee.duke.edu/~cummer/reprints/132_Han11_JGR_DaytimeDRegionSharpness.pdf  ) recently showed considerable and substantial disagreement (qualitative and quantitative) between beta* parameters values derived (empirically) by a number of expert sources including Thomson. Han?s findings are well-summarized on the last page of his paper. The kind of discrepancies shown by Han seem (to me) suggest a lot of work remaining on the way to good diurnal amplitude and phase models. Among the four expert sources on D-region beta cited by Han, there were three different findings on the polarity of the change in beta with zenith angle:  decreasing beta with increasing zenith angle (1 of 4), increasing beta with increasing zenith angle (2 of 4), relatively constant beta with increasing zenith angle (1 of 4); not to mention considerable disagreement between the four sources in magnitude of sensitivity of beta to zenith angle. All of this is clearly summarized on the last page of the paper.

 

I thought you might find the paragraph above interesting because it shows a significant gap in the understanding of some basics that affect (at some distances and on some days) whether VLF daytime signal strength increases or decreases. In his conclusion, Han describes the magnitude of  disagreement in derived values for beta as surprising. He suggests that the two-parameter model may not be sufficient (a circumstance that Thomson hoped to avoid, see above)

 

On a related topic, Han?s method of deriving beta (using broadband signals) is interesting and appears to have substantial merit, but I?m guessing that the available broadband sources used by Han (sferics) come with their own issues in this type of measurement.

 

I think I can end on a light note: if you have a chance to look at one figure and one paragraph in this paper by Volland: http://nvlpubs.nist.gov/nistpubs/jres/68D/jresv68Dn2p225_A1b.pdf , Adobe Reader page 4 (document page 228), including Figure 3 and the paragraph including ?A remarkable exception from this rule has been observed in Lindau (Germany), Figure 3 shows two successive daily phase variations of GBR? Such phase inversions are rare??, I think you may find something interesting, odd or even humorous.

 

  *  (D-region electron density sharpness)

 

Regards,

 

Jim

 

<Prev in Thread] Current Thread [Next in Thread>