[HCARC] Propagation

[Kerry Sandstrom]

Bruce,

I'm glad you got something out of the propagation discussion.  I haven't 
looked at the ARRL propagation bulletins in a few years.  What I remember of 
them is there are specific paths from various locations in the US to various 
DX locations with the best frequency every hour or two for that path.  They 
are generated using one of the propagation models.  In the old days, the 
model used was the large FORTRAN model from ITS that ran on a main frame.  I 
expect they are using VOACAP or a commercial version of it now.  I expect 
the reason that you can't relate what I said to  those charts is because 
they really aren't related.  I tried to describe the ionosphere and then 
give you a little idea of how our signals behave in the evening.  This is 
because the discussion at the time involved NVIS and 40 meters and why it 
isn't good for local activity after dark and why NVIS won't work on 40 m 
after dark, particularly in the winter.  The ARRL bulletin on the other hand 
is looking at particular DX paths.  You see some of the same changes but 
only on one path and you lose the overall effect that we see on our bands.

I don't know of a single source for that information.  A lot of it came from 
articles in the old Proceedings of the Institute of Radio Engineers, now 
part of the IEEE.  Most of the basic work was done in the 30's and 40's.  A 
second wave of research was done during the IGY around 1957.  The old 
articles are quite readable for any technically interested ham but not easy 
to find.  You have to have access to a good technical library , which I no 
longer do.  I actually think the ARRL Handbooks and Antenna Books from the 
50's and 60's give better presentations than the modern versions.   The 
Proceedings of the IRE are an excellent source.  Another excellent source is 
the Journal of Geophysical Research, series A, I believe, from the same 30's 
through 60's period.  There are numerous "textbooks" which are not as 
readable for anyone but do show the underlying theory and equations.

After Antennas, propagation is probably the area of ham radio that is most 
full of nonsense!  There is nothing magic.  For every effect there is a 
cause and we can understand it.  My suggestion would be if you have an area 
you would like to learn about, go to the internet and search.  I try to find 
references to older articles and try to find those articles.  It takes a 
while but it is something I've always enjoyed doing.  Often one article will 
lead you to another.  And best of all, I got my uncle to pay me to do a lot 
of it!  You have to be in the right place at the right time.  And my uncle 
is still paying me to do it but only part time.

73,

Kerry