OH1TV   OH1O   OH1WX
	Critical frequency foF2-limited local QSO on 28.5MHz
		When F2 layer height = 250km
		Ionogram	Shortest			Corresponds to 3000km
		foF2	distance	TOA		MUF	TOA
		7.76	3500	0.1		28.5	2.5
		8.00	2720	4.1		29.0	2.5
		9.00	1965	9.6		32.7	2.5
		10.0	1610	13.3		36.3	2.5
		11.0	1375	16.5		39.9	2.5
		12.0	1201	19.5		43.6	2.5
		14.0	951	25.1		50.8	2.5
		16.0	772	30.7		58.1	2.5
		18.0	633	36.3		65.3	2.5				TOA = antenna take off angle
		20.0	519	42.2		72.6	2.5
		22.0	418	48.6		79.9	2.5				Critical frequency foF2 link
		24.0	323	55.9		87.1	2.5
		26.0	226	64.7		94.4	2.5
		27.0	170	70.5		98.0	2.5
		28.0	0	90.0		101.6	2.5
		MHz	km	deg		MHz	deg
		Observations:
		Band is closed when foF2 is less than 7.8MHz
		Very short ,few tens of kilometers, QSO via F2 is possible when foF2 is 28MHz or more
		QSO down to 1000km is possible via F2  when foF2 is 13.4MHz
		QSO impossible to distances less than 2000km when foF2 is 9MHz or less. DX is coming fine but out own continent not.
		QSO may still be possible via other propagation modes like back scatter, F1 etc.
		Back											28.4.2012