OH1TV   OH1O   OH1WX
	Critical frequency foF2-limited local QSO on 3.7MHz
		When F2 layer height = 250km
		Ionogram	Shortest			Corresponds to 3000km
		foF2	distance	TOA		MUF	TOA
		1.0	3500	0.1		3.7	2.5
		2.0	820	29.0		7.3	2.5
		2.5	559	40.0		9.1	2.5				TOA = antenna take off angle
		3.0	365	52.5		10.9	2.5
		3.5	172	70.3		12.7	2.5				Critical frequency foF2 link
		3.6	119	76.1		13.1	2.5
		3.67	63	82.5		13.3	2.5
		3.7	0	90.0		13.4	2.5
		MHz	km	deg		MHz	deg
		Observations:
		Band is closed when foF2 is less than 1MHz
		Very short ,few tens of kilometers, QSO via F2 is possible when foF2 is 3.7MHz or more
		QSO down to 200km is possible via F2  when foF2 is 3.4MHz
		At daytime D-layer may hinder QSO even foF2 is high enough
	Back												28.4.2012