[TowerTalk] re Take off angles - especially for LF work

[n4kg@juno.com]

N4KG comments inserted between paragraphs.

On Thu, 21 Dec 2000 10:22:29 +1100 (EST) Peter Forbes
<prforbes@tbsa.com.au> writes:
> To the list,  
> 
> I have been following with interest the various exchanges regarding 
> the effect of takeoff angles especially regarding the lower HF bands.
> 
> It is all quite scientific, but I have a far more scientific method 
> of> predicting the peak times/closing times, especially for westward 
> paths at sunrise.
> 
> 
> 160 metre opening - once it is light enough to read the headlines on 
> the newspaper outside, the band has closed

	N4KG:  Usually true.  
> 
> 80 metre opening - once it is light enough to read the fine print on 
> the newspaer outside, the band has closed

	N4KG:  NOT  SO.  This the mistake VK0IR made.
	My observations are that signals begin to rise at
	sunrise (Sun on horizon, past first light) and peaks
	to the West 10 to 30 minutes past SR. 

	One SUMMER, I heard FR5DX on 75M LP an 
	hour and a half past my SR (and about the same
	amount of daylight before his SS).  MUF (and 
	absorption) rises more slowly in summer months.

	BTW, the hour BEFORE SR can be be the WORST
	hour of the day, especially to the West.  Weaker
	stations from the Pacific are often inaudible before
	SR (working other stations to my east) but come up 
	nicely at my SR.  I remember sitting on 3798? hearing
	East Coast stations working XX9-- a their SR, following
	the SR from W1 to W4 but not a peep here until my SR
	at which time he came up enough to make contact and
	disappeared a few minutes later as the W5's began 
	working him.   de  N4KG
> 
> 40 metre opening - once the birds stop twittering the band has 
> closed.
> 
	40M usually peaks from 30 to 60 minutes past SR.
	I have heard Pacific / SE Asians as late as 3 hours
	past my SR during low sunspot levels.  de  N4KG

> 30 metres opening - add 1 hour for summer, 2 hours for 
> spring/autumn, add 3 hours for winter to 40 metre times.
> 
> 
> Laugh if you will, but in 40 years of DXing, the rule has never 
> failed me!!!!
> 
> 
> I am carrying out extensive scientific analysis on formulating a 
> rule for
> sunsets propagation to the east.  Findings will be released soon.
> North/south paths present more problems such as what the hell is 
> going on in the ionosphere/geomagnetic field !!!
> 
	Signals arriving perpendicular to the approaching 
	Sunset terminator can be heard before SS (an hour
	or more on 40M).  As the terminator gets closer,
	signals from further south can be heard.  During
	the twilight period, LP signals from East / SE Asia
	can be heard.  These LP openings typically last
	for 5 to 15 minutes on 80M, longer on 40M, perhaps
	up to an hour.  de  Tom  N4KG

> Cheers and happy DXing
> 
> Peter  VK3QI   
> 

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