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Topband: Re: Puzzeling Propagation

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Subject: Topband: Re: Puzzeling Propagation
From: (Bill Tippett)
Date: Wed, 11 Aug 1999 19:01:48 +0100
K1FK wrote:

>On 6 August, 1999, I began hearing HZ1AB on 1822 just above the noise
>beginning at about 0135 UTC.  His signal slowly increased to an S7 at 0145
>UTC, at which time I called once and he responded with a 559. His signal
>(he was still calling CQ) gradually decreased and completely disappeared
>into the noise again at 0157 UTC.  There were no signs of QSB (either rapid
>or slow) on his signal during the entire period.
>The next day I received an email from Thomas, SM0CXU, the guest operator at
>the HZ1AB club station, who confirmed the QSO and suggested that we had
>experienced excellent gray line propagation.  He was in the SR end of the
>gray line at that time, but it was 2-hrs 44-min past my SS here in northern
>Maine and I was clearly out of the gray line "zone" by more than 2 hours at
>this end of the circuit.

Hi Dave!  Congrats on HZ1AB!  I heard him several times earlier this year
but never been able to get him to hear me.  Since I have his sunrise as 
0205 on 1 August, he probably thought it was greyline.  In fact, this
should more properly be called "sunrise enhancement" (just like what
we experience to JA or VK at our sunrise) since only one end of the path
is in twilight.  True "greyline" normally refers to the situation where
both paths are near twilight, so Thomas was probably just using the wrong

>What is more puzzling to me is that if this were a true great-circle path,
>over 40% of my end of the circuit was "skirting" just outside ofthe auroral
>oval and over 50% of my end of the circuit was through latitudes of 50N or
>more, and a small portion was through the auroral oval being displayed at
>the SEC site.  I'm located at 47.252N.
>Any thoughts as to what propagation mechanisms may have been involved?  

I checked the WWV numbers for 0 UTC on 6 August (I assume you were using
the correct UTC date and didn't actually mean local evening of 6 August which
is 7 August UTC) and the K index was 2 indicating a mildly disturbed
geomagnetic field.  In this situation, I would not be surprised if the path
was skewed slightly south due to the disturbance.  Could you tell which 
direction the signal was coming in from?  If it was south of your great circle
bearing, it may have been skirting the auroral oval to the south.  See page 11
of the August '99 issue of CQ for a discussion of this mechanism by K9LA.  

I hope this helps and I'm posting my response to the reflector also since others
might be interested or want to comment.

73,  Bill  W4ZV

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