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	Local QSO's on 40m and other HF-bands
	In the higher latitudes, 60deg N and more, 40m band conditions are not always suitable for local contacts.
	During sunspot minima possibilities are rather limited but during maxima a bit better.
	The critical frequency foF2 stays often below 7MHz, which means that local contacts on 40m with high take-off-angles are at risk.
	But with distance useful frequency increases from the critical frequency and MUF may reach the band.
	The same phenomena happens also on other HF-bands: DX-stations can be stronger than locals.
	In order to better understand, when communication is possible and how far the other stations shall be, I made some calculations.
	I used the TOA-calculator I had developed earlier and which is presented here on my pages as project 26.
	I assumed  the F2-layer to be on height of 250km.
	The needed critical frequency is available in near real time from ionograms and as a world wide map from VK-land here:
	foF2 map
	My results are presented in table form and graphs:
	Local QSO on 7MHz
	Local QSO on 3.7MHz
	Local QSO on 14.2MHz
	Local QSO on 28.5MHz
	D-layer attenuation, which disturbs on 80m even when critical frequency foF2 is higher than band frequency, is not considered here.
	On the file is also shown take-off-angle of a horizontal antenna as function of antenna height.
	Pekka
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	28.4.2012