TopBand: RE: Poor 160 Conditions

[w8ji.tom]

Hi Bob,

> There is more than enough ionization overhead to support 160 meter
> propagation.  Put another way, MUFs are not an issue.  Period.  But
> magnetic activity with higher SSNs continues to be a problem, even at
> mid-latitudes.

Everything I've read indicates signal levels drop as frequency is moved
further below the MUF, and the strongest signals occur just below the MUF.
It is in the Antenna Engineering Handbook section on propagation and also
in other engineering textbooks. They lay the blame to increased absorption
as frequency is decreased below the MUF.

Is that incorrect in some way?

> 1) a slight rise in ionospheric absorption during quiet days, just as
> there is a slow rise in foE with increasing SSN.  You will see this in
> Figure 5.13 in Davies' new book.
> 
> 2) there will be a slight increase in the radiation angle needed to get RF
> past the peak of the E-region at night.  That is the case as the effective
> vertical frequency must increase to go along with the slight change in
> foE at night.  The rise in foE means that more RF goes on E-hops, with
> accordingly greater signal losses for a given power output.

The above two statements seem to support the fact that if MUF is high (from
an increased SSN, which also pushes up MUF) on a given circuit, LUF will
also increase. What am I missing?

73 Tom


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