On Sun, 26 Sep 2004, NW7US, Tomas wrote:
> > How does the MUF map predict availablity of a DX path
> > for 80 Meter QSOs (which was the original question),
> > or for 160 Meters?
> ........
> This question (propagation on 80 and 160, and models used to forecast) is
> not addressed well in the VOACAP/IONCAP models. There are other models
> that some software offerings incorporate to help in detailing signal paths
> for MW propagation. Proplab and SnapMAX are two such examples. .....
Tomas has stirred me up here to take look at the "mfsignal" subroutine I
wrote for SnapMAX & I've finally gotten round to looking to see what were
the references that I used for the MF algorithms.
The basic info. was based on a curve used by the International Frequency
Registration Board when looking at European MF broadcasting allocations in
the band 285 - 1605 KHz, and also on a similar FCC curve. These, with some
others are shown in the book "Propagation of Waves" by David and Voge
(Pergamon) where the discrepancies between this and other data are also
looked at. This is for night propagation and needs massaging for daytime
and that came from Davies book "Ionospheric Radio" (Peregrinus), or so my
program comment lines say! The final algorithm also looked at E layer
incidence angle and the mid-point gyro frequency (which comes from a map
built into the program).
Which is all very well, and tied in with a good number of known examples,
but the real guesstimate was on how to ease those numbers into the HF
region calcs. Where does MF stop and HF start??? I was fairly arbitrary,
after some head-scratching, and again checking with some examples that
seemed to be a fair sample, I settled on saying that below 1.9 MHz was
pure MF propagation, while above 3.9 MHz was "pure" HF, and in between I
fudged the answers as a proportion, using a 50/50 mix of the two calcs. at
2.9 MHz. It's probably a good thing there's no ham band between 80 & 160!
Not very technical, but I could find no better answer at the time, and
have had no user feedback to say it doesn't work. Any comments on any of
that would be welcome.
73, Crawford WA3ZKZ/VP8CMY
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