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	Minimum fo for  50MHz  band opening
	6m openings are always exciting. But they do not come out of blue. One can monitor the development from ionograms.
	When foF2 or foEs rise high enough, the band opens. But how high shall they grow?
	I used my TOA- and MUF-calculator from project 26 to find out.
	The band opens with low angles first, when fo is building, from 0 deg take-off-angle on. This has been my band opening criteria.
	Below are the results of calculations as function of layer height in table form, assuming TOA=0.
	The same is presented in graphs as well. Use Excel index below:
	A	Minimum critical frequency fo as function of layer height for 50MHz band opening
	B	Single hop station distance with 0 deg take-off angle as function of layer height, any frequency
	C	MUF-factor as function of layer height, any frequency
	D	Minimum distance between stations as function of foEs, when Es-layer is in height of 120km . (separate table)
	E	Minimum distance between stations as function of foF2, when F2-layer is in height of 250km . (separate table)
	F	Optimal antenna height for 50MHz Es contact, when Es-layer is in height of 120km
	Critical frequency fo ionogram data is available					here	and here.
	Measurements are made every 15 minutes. For good use of foEs observations the station network is not dense enough.
	17.5.2012
	Pekka, OH1TV
	Minimum fo for 50MHz band opening, TOA=0 deg
		h	fo	d	MUF-factor
		50	6.23	1590	8.03		h =  height of reflecting layer / km, from ionogram
		75	7.61	1940	6.57		fo = critical frequency from ionogram to give MUF=50MHz
		100	8.76	2240	5.71		d = distance between stations / km, valid on any frequency
		150	10.67	2730	4.69		MUF-factor =  this multiplied with fo gives MUF, valid on any frequency
		200	12.25	3150	4.08
		250	13.61	3510	3.67		TOA= take-off-angle of signal path
		300	14.83	3830	3.37
		350	15.93	4120	3.14
		400	16.94	4400	2.95
		450	17.87	4650	2.80
		500	18.73	4880	2.67
		km	MHz	km
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													17.5.2012